FIELD OF THE INVENTION

The present invention relates to a thermal management device for heat generating component, such as powered components that consume DC or AC power, and in particular electrical or electronic heat generating components

DISCUSSION OF RELATED ART

It will be appreciated that equipment, and in particular powered equipment has an optimum operating temperature. Equipment such as electrical and electronic equipment is often deployed in industrial environments which may serve to heat or cool those components. Operation of equipment within a preferred temperature window; may assist with long term maintenance of performance and efficiency, and ensures that stated equipment design lifetime can be met. Operating equipment above or below a manufacturer's approved range may reduce operational efficiency and may significantly reduce the lifespan of such equipment, leading to equipment failure and potentially significant maintenance costs.

It is known to provide cooling apparatus, for example fans or the like equipment, to dissipate built up heat in operational systems. Such cooling apparatus typically operate intermittently and use convection or other means to cool the equipment with air. However such cooling typically requires some source of power, which is not ideal because this is a further heat source. Often equipment is mounted in arrays or cabinets for example to protect it from external elements such as weather etc. Enclosing the equipment in such a way exacerbates the heating issue. Furthermore the enclosure, such as a rack or cabinet may leave little room for cooling equipment to be effective. It is desired to provide a means of addressing issues with thermal management of equipment.

SUMMARY

Accordingly, a first aspect provides a thermal management device for heat generating components comprising: a thermally conductive structure coupleable to a heat generating component and operable to provide a thermal path between the heat generating component and a thermoelectric module; the thermoelectric module being operable to transfer heat between itself and the thermally conductive structure to maintain temperature of the heat generating component within a predetermined range. Thermal management devices that are battery thermal management devices are not within the scope of the present invention. Electrical or electronic components that are within the scope of the present invention do not include batteries.

One possible solution to optimizing operating temperature of heat generating components is to provide the heat generating components with their own enclosure, thus separating the heat generating component from the surrounding environment. That physical separation of heat generating components from the surrounding environment, whilst having advantages, also has associated difficulties as mentioned above. In such an arrangement, for example, a thermoelectric module (for example, a thermoelectric cooler), may be employed to cool air within the enclosure. The thermoelectric cooler cools air in direct contact with a cold plate and a fan is employed to push that air around heat generating components within the enclosure. Use of air as a cooling medium in such solutions may be particularly inefficient and the pushing of that cool air over heat generating component within an enclosure typically occurs by use of fans. Fans inevitably have moving parts and tend to be unreliable, particularly when exposed to elevated temperatures. The failure of cooling solutions involving movement of cold air via fans is thus likely and maintenance and repair of such solutions can prove costly.

Furthermore, it will be appreciated that installation and maintenance costs for large industrial sites for use in the event of equipment failures can be particularly large.

Large industrial deployments may have various electronic and other equipment.

Components of that equipment typically each have an optimum working temperature.

For example, in a telecommunications base station, general cooling of an equipment area may occur either by arrangement of appropriate air entry and exit points, associated with appropriate fans, and/or by use of appropriate air conditioning.

Telecommunications or other equipment may have an maximum operational temperature for example, as dictated by a manufacturer. Provision of a separate housing for any equipment operating at a significantly different temperature may be considered to offer a solution which can negate the need for provision of constant air conditioning, thereby saving a degree of electrical consumption within such an industrial equipment environment. In overview, the first aspect allows for removal of an external housing or enclosure and negates a need to use fans. Such active components are replaced with predominantly passive components such as heat pipes and thermoelectric modules as described in more detail with reference to further embodiments, to provide a heat generating component cooling and heating solution thus offering thermal stabilisation to equipment operation in an industrial deployment. It is believed that embodiments offer a solution which can be inexpensive, lightweight, reliable and which may be retro fitted to equipment deployments in industrial environments. The first aspect provides, with appropriate choice of components, a means of providing a substantially passive means of heat extraction and heat transfer, thereby reducing power consumption expended in comparison to an active thermal management solution. It will be appreciated that the supply of power to thermoelectric modules may be considered an active step, but that the heat transfer is substantially passive.

According to one embodiment, the thermally conductive structure is arrangeable adjacent to at least a part of a surface of the heat generating component.

Accordingly, by arranging the thermally conductive structure adjacent to at least a part, or substantially the entire surface of a heat generating component, heat transfer can be directed to precisely where it is required, ensuring that operation of the heat generating component is optimised.

According to one embodiment, the thermally conducive structure is coupleable to the heat generating component via a thermally conductive paste. Accordingly, it will be appreciated that the structure may be thermally coupled to the heat generating component in a number of ways. There may be a direct physical connection, it may be placed adjacent to the surface, or may be affixed by means of a thermally conductive paste, direct contact, or other similar means. In each case thermal transfer between the heat generating component and structure may be optimised.

According to one embodiment, the thermally conductive structure is operable to spread thermal load across at least part of a surface of the heat generating component. Accordingly, by spreading thermal load across at least a portion of a heat generating component surface, thermal management of the heat generating component may be more efficiently implemented, since heat transfer may be effected across a greater surface area. Accordingly, a greater heat generating component temperature stability may be achieved. The structure may, in some embodiments, be a heat spreader. According to one embodiment, the thermally conductive structure comprises a† least one thermally conductive plate arranged adjacent to at least a part of a surface of the heat generating component. That thermally conductive plate may comprise a substantially planar metallic sheet. According to further embodiments, heat pipes or shunts may be appropriately dimensioned to negate a need for a separate heat spreader plate. That is to say, heat pipes may be placed in contact with at least a part of the surface of the heat generating component for heat load transfer.

According to one embodiment, the thermally conductive plate is coupled to the thermoelectric module. By directly coupling or connecting a heat spreader to a thermoelectric module, thermal stability of heat generating components may be more efficiently implemented. According to one embodiment, the coupling between the thermally conductive plate and the thermoelectric module comprises a direct connection. It will be appreciated that according to some embodiments connections and thermal coupling may be made between components using thermally conductive paste or similar.

According to one embodiment, the coupling between the thermally conductive plate and the thermoelectric module comprises at least one heat pipe operable to provide a heat path between the conductive plate and the thermoelectric module. Use of heat pipes provides an efficient passive means of transferring heat within a temperature management device.

According to one embodiment, the thermally conductive structure comprises at least one heat pipe which provides the thermal path between the heat generating component and the thermoelectric module.

According to one embodiment, a heat sink is coupled with the thermoelectric module and operable to dissipate heat. Accordingly, heat dissipation from the device may be optimised.

According to one embodiment, the coupling between the heat sink and the thermoelectric module comprises a heat shunt or pipe operable to provide a thermal path between the thermoelectric module and the heat sink. According to one embodiment, the device comprises a retrofit module for installation between adjacent heat generating components. Provision of a modular device allows implementation of a thermal management solution which is flexible across heat generating component deployments. According†o one embodiment, the device is integrally formed with at least one heat generating component. Accordingly, a heat generating component or components may be manufactured to include a device according to embodiments.

According to one embodiment, the device further comprises feedback control logic, operable to monitor heat generating component temperature and compare that temperature with said predetermined range. If it is determined that the heat generating component temperature lies outside said predetermined range, operational temperature of the thermoelectric module may be adjusted according to a predetermined increment. The effect of that incremental change may be monitored to see whether further temperature changes are required to stabilise the heat generating component operating temperature within the predetermined range. According to some embodiments, ambient environment temperature may be monitored and taken into account in the feedback logic unit. Furthermore, in an industrial deployment, it will be appreciated that the heat generating component feedback thermal monitoring unit may form part of a larger industrial thermal control unit. A second aspect provides a method of thermally managing a heat generating component comprising:

providing a thermally conductive structure coupleable to a heat generating component and operable to provide a thermal path between the heat generating component and a thermoelectric module;

providing a thermoelectric module arranged to transfer heat between itself and the thermally conductive structure to maintain temperature

. of the heat generating component within a predetermined range.

According to one embodiment, the thermally conductive structure is arranged adjacent to at least a part of a surface of the heat generating component.

According to one embodiment, the thermally conducive structure is coupled to the heat generating component via a thermally conductive paste. According to one embodiment, the thermally conductive structure is arranged to spread heat load across at least part of a surface of the heat generating component. According†o one embodiment, the thermally conductive structure comprises at least one thermally conductive plate arranged adjacent to at least a part of a surface of the heat generating component. According to one embodiment, the thermally conductive plate is coupled to the thermoelectric module.

According to one embodiment, the coupling between the thermally conductive plate and the thermoelectric module comprises a direct connection.

According to one embodiment, the coupling between the thermally conductive plate and the thermoelectric module comprises at least one heat pipe arranged to provide a heat path between the conductive plate and the thermoelectric module. According to one embodiment, the thermally conductive structure comprises at least one heat pipe arranged to provide the thermal path between the heat generating componentand the thermoelectric module.

According to one embodiment, the method comprises coupling a heat sink with the thermoelectric module and operable to dissipate heat.

According to one embodiment, the coupling between the heat sink and the thermoelectric module comprises a heat shunt or pipe arranged to provide a thermal path between the thermoelectric module and the heat sink.

According to one embodiment, the method comprises retrofitting the device as a module between adjacent heat generating components.

According to one embodiment, the method comprises integrally forming the device with at least one heat generating component.

A thermal management device of the invention may comprise a carrier and a plurality of thermally conductive structures projecting as fingers from the carrier and arranged to provide a plurality of thermal paths between one heat generating component or a plurality of heat generating components and respective thermoelectric modules. Such a device may comprise a thermally conductive structure coupleable to the heat generating component and operable to provide a thermal path between said heat generating component and a thermoelectric module; said thermoelectric module being operable to transfer heat between itself and said thermally conductive structure to maintain temperature of said heat generating component within a predetermined range, but provided that the thermal

management device is not a battery thermal management device and/or that the electrical or electronic component is not a battery.

A thermal management device of the invention may thus comprise a retrofit module comprising a plurality of thermally conductive structures arranged to provide a plurality of thermal paths between one heat generating component or a plurality of heat generating components and respective thermoelectric modules. This means a given piece of equipment may be cooled at a plurality of locations, or plurality of equipment may be cooled, each at one location. It will be appreciated that it is also possible to cool a plurality of pieces of equipment each at a plurality of locations. A thermal management device of the invention may be configured as a retrofit module suitable for any such cooling applications. The module may be adapted to be slidably inserted, for example by means of a carrier as described above, into an array of equipment for example above or below, or to one side of a heat generating component. In one arrangement the module is carried on a rail for insertion into and removal from the array. Desirably the rail is coupleable to the array.

In a thermal management system according to the invention the heat generating component(s) may be selected from any heat generating equipment: computing equipment, telecoms equipment, motors, switches, relays, routers, transformers, control systems, analogue devices, digital devices, electronic boards, etc.

Such a system is easily adapted for different purposes, for example the number and spacing of the heat pipes can be varied. The carrier may be thus easily adapted for fitting to different arrays. Furthermore the device can be adapted for the array to which it is fitted for example by providing suitable connection points etc.

Further particular and preferred aspects of the present invention are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure 1 illustrates schematically main components of a heat pipe for use in embodiments;

Figure 2 illustrates schematically main components of a thermoelectric module for use in embodiments;

Figure 3 is an exploded perspective view of a temperature management solution for an electronic or electrical heat generating component according to one embodiment; Figure 4 is an exploded perspective view of a temperature management solution for an electronic or electrical heat generating component according to one embodiment;

Figure 5 is an exploded perspective view of a temperature management solution for an electronic or electrical heat generating component according to one embodiment;

Figure 6 is an exploded perspective view of a temperature management solution device for an electronic or electrical heat generating component according to one embodiment;

Figure 7 is an exploded perspective view of an alternative temperature management system of the invention and an array (stack) of heat generating components;

Figure 8 is a perspective view from the front and to one side of the alternative temperature management system of the invention of Figure 7; and

Figure 9 is a perspective view of the temperature management system of Figure 7 inserted into an array (stack) of heat generating components.

DESCRIPTION OF THE EMBODIMENTS

In overview, embodiments provide a temperature management assembly for an electronic or electrical heat generating component which does not require a physical enclosure surrounding the heat generating component, and does not require use of fans to move air around heat generating components or to remove heat from a heat sink. Embodiments provide a passive heat management system comprising heat pipes and thermoelectric modules, thereby providing an inexpensive, lightweight, reliable and potentially modular heat management assembly which may be retro fitted to existing heat generating component deployments.

It will be appreciated that heat generating components such as electrical or electronic components have an optimum operating temperature. Operation of heat generating components within a preferred temperature window; may assist with long term maintenance of component performance and efficiency, and ensures that stated component design lifetime can be met. Operating heat generating components significantly above or below a predetermined optimum temperature; may significantly reduce the lifespan of such a heat generating component, leading to equipment failure and potentially significant maintenance costs. Embodiments described herein predominantly use passive components such as heat pipes and thermoelectric modules to provide a heat generating component cooling and/or heating solution. The use of passive components may be less expensive, weigh less and be more reliable than solutions relying on air circulation options. Passive component systems may also negate a need for use of fans or air conditioning to provide temperature stabilisation to heat generating components. Moreover, a passive component system may also be retro fitted to existing deployments in industrial environments.

Before discussing the assembly in detail, an explanation will first be given of some of the main components of the assembly.

Figure 1 illustrates schematically an example of a heat pipe which transports and transfers heat from a heat source. The heat pipe 1 comprises a casing 10 which surrounds a wick 20 which in turn, surrounds a vapour cavity 30.

A heat pipe thermal cycle occurs as follows: At point A at a high temperature, working fluid evaporates to vapour, thus absorbing thermal energy. At point B the vapour migrates along the vapour cavity 30 towards a lower temperature end. There is a temperature gradient in the direction of arrow E in Figure 1 . At point C in the heat pipe thermal cycle, vapour condenses back to a fluid and is absorbed by wick 20, thereby releasing thermal energy. As indicated by arrows at point D, the working fluid then flows back towards the high temperature end. It will be appreciated that heat pipes efficiently transfer heat energy from regions of heat to a region of cooler temperature without the requirement to actively pump or move the working fluid. Vapour condenses releasing thermal energy and is then absorbed by the wick structure 20, and can return to the evaporative end of the heat pipe structure.

Figure 2 illustrates schematically an arrangement of a thermoelectric module 100. The structure of the thermoelectric module (TEM) 100 is such that it includes n-doped pellets 1 10 and p-doped pellets 120. Pellets 1 10, 120 are connected by sets of electrodes 130 and 140. The pellets 1 10, 120 and electrodes 130, 140 are configured to be electrically in series and thermally in parallel. Upper and lower substrates 150, 160 serve to electrically isolate the thermoelectric module from an object with which the thermoelectric module 100 is placed in thermal contact, and to provide mechanical strength. The substrates 150, 160 may be formed from an electrically insulating ceramic with a sufficiently high thermal conductivity such as, for example, Alumina, aluminium nitride or beryllia (beryllium oxide).

The efficiency of heat transfer by the thermoelectric module decreases with increasing heat flux across the pellets 1 10, 120. By applying a voltage potential across the semiconductors, substrates 150, 160 become either hot or cold. In the illustrated example, plate 150 is the cold side and absorbs heat, and plate 160 is the hot side and releases heat. That is to say, the thermoelectric module can act as a heat pump.

A thermoelectric module such as that illustrated in Figure 2 can provide controlled heating or cooling on the condenser or evaporator end of a heat pipe such as that illustrated in Figure 1 . It will be appreciated that low power loads, compared to those loads used to drive fans or electric air conditioning units, can be required to drive the thermoelectric module of Figure 2 since a temperature difference of only a few degrees between ends of a heat pipe can allow efficient heat pipe operation.

Figure 3 is an exploded perspective view of a thermal management solution for heat generating component according to one embodiment. Heat generating components 1000 which are typically arranged in close proximity to each other, often times side by side or stacked, one on top of the other, may be cooled passively by a heat generating component cooling assembly 300 comprising heat pipes 310 and thermoelectric modules 320 mounted on a support plate 330. According to the embodiment shown in Figure 3, heat pipes 310 are arranged to fit between and adjacent to heat generating components 1000. Those heat pipes may directly contact the heat generating components thereby removing a heat load from the heat generating components. Heat load is transported via heat pipes 310 to the thermoelectric modules 320 mounted on support plate 330. It will be appreciated that heat pipes 310 are also mounted on support plate 330, but that the exploded perspective view of Figure 3 is such that the connection is not shown.

Such a heat generating component cooling solution may provide both heating and cooling of heat generating components 1000 at a relatively low power cost. The cooling offered by cooling assembly 300 is substantially passive. It will be appreciated that the thermoelectric modules may be connected to a voltage source and that temperature sensors may be provided on the heat generating components and connected into a feedback electronic loop also connected to the thermoelectric modules†o ensure that the heat generating component temperature is maintained at a substantially constant value. Furthermore, it will be appreciated that a heat sink may be provided attached to the thermoelectric module and support plate such that heat loads from the thermoelectric module can be dissipated to ambient air. Such an assembly can act to cool the heat generating components when required, for example if the outside temperature is high and heat the heat generating component when required, for example if the ambient temperature is determined to be too low.

Figure 4 is an exploded perspective view of a cooling assembly for heat generating components according to a further embodiment. Cooling assembly 400 comprises generally heat pipes 410, thermoelectric modules 420 supported on a support plate 430 and spreader plates 440. In the embodiment shown in Figure 4, spreader plates 440 are placed between and in contact with heat generating components 1000. Those spreader plates are made from a thermally conductive material and act to remove heat load from the heat generating components and spread that heat load evenly across the spreader plates. Heat pipes 410 are sandwiched within the spreader plates and are operable to transfer heat load from the spreader plates to the thermoelectric modules above. The thermoelectric module generates a cold side temperature that causes heat at the thermoelectric module side of each heat pipe to condense, thus releasing its heat energy and controlling the temperature of the heat generating components 1000. Heat load from the thermoelectric modules may be dissipated to the air by means of a heat sink (not shown). Such an embodiment may act to cool heat generating components if outside temperature is high, and heat the heat generating components if outside temperature is low, by provision of a feedback circuit and appropriate monitoring sensors for example provided at the heat generating components and/or in the region of thermoelectric modules 420. It will be appreciated that provision of the spreader plates allows for an increased surface area for heat transfer from and to heat generating components 1000. Figure 5 is an exploded perspective view of a cooling assembly for heat generating components according to a further embodiment. The cooling assembly 500 comprises spreader plates 540, heat pipes 510 and thermoelectric modules 520 mounted on a support plate 530. The embodiment shown in Figure 5 is modular and flexible and thus offers robustness to many variations of deployment of heat generating components in the field. Again, the basic idea is that the spreader plates, which are thermally conductive and, for example, made of metal, may be placed between and in contact with heat generating components 1000. Those spreader plates are operable to remove heat load from heat generating components and spread that heat load across the spreader plates. Heat pipes 510 are then sandwiched between the spreader plates and are operable to transfer heat load from those spreader plates 540 to the thermoelectric modules provided on support plate 530. It will be appreciated that although Figure 5 shows deployment such that the thermoelectric modules are provided on the top of the heat generating components, they could also be provided at any suitable position proximate the heat generating components, for example on a front plate, arranged to slot between adjacent heat generating components horizontally rather than vertically.

As described previously, the thermoelectric module is operable to generate a cold side temperature that causes the heat at the thermoelectric module side of heat pipes to condense, thus giving off its heat. In such a way, the temperature of the heat generating components may be controlled. The heat load from each thermoelectric module may be dissipated to the air via a heat sink (not shown in the Figure for clarity) .

Figure 6 is an exploded perspective view of a cooling assembly for heat generating components according to a further embodiment. Cooling assembly 600 comprises thermoelectric modules 620, heat pipes 610 and a heat sink 660. In this embodiment, thermoelectric modules 620 are arranged between heat generating components 1000. Heat spreaders are provided that have been removed from Figure 6 for clarity. In the solution shown in Figure 6, thermoelectric modules are provided such that their cold side contacts spreader plates, thereby cooling them. Those spreader plates transfer the cold temperature to the heat generating components and thereby act to regulate temperature of the heat generating components. One particular benefit of an arrangement according to Figure 6 is that a hot side of a thermoelectric module is provided in direct contact with heat pipes 610, thereby improving efficiency of heat pipe operation to transport heat. Heat transferred by heat pipes 610 from the heat generating components via thermoelectric modules 620 is dissipated to the air via heat sink 660.

The embodiments shown in Figure 6 may provide good temperature control at a hot surface of heat generating components 1000. It will be appreciated that the embodiment of Figure 6 offers a means of temperature control rather than significant heat dissipation. Heat pipes 610 are operable to control the temperature of heat generating components 1000. The heat load from each thermoelectric module hot side is dissipated to the ambient air via a condenser section of heat pipes 610. I† will be appreciated that the embodiment illustrated in Figure 6 may also operate to heat the heat generating components, as has been described previously in relation to other embodiments. It will be appreciated that embodiments described relate to generally passive systems which have no moving parts and thus offer a low maintenance or no maintenance cooling solution for heat generating components deployed in an industrial environment. Modular solutions such as those shown in Figures 5 and 6 offer a relative plug-and-play capability and the ability to retro fit to existing equipment deployments. Heat pipes at thermoelectric modules offer large heat transfer capability and an opportunity for good thermal uniformity whilst only using a low parasitic power as a result of low power requirements of thermoelectric modules.

Embodiments reduce the possibility of thermal runaway and are operable to heat heat generating components in reduced ambient conditions, thereby offering temperature stabilization apparatus. Furthermore, in contrast to known solutions, heat generating components are not enclosed for the purposes of fan cooling and thus there is better natural cooling also. Embodiments provide a natural thermal isolation without the need for physical isolation.

Although embodiments of the present invention are described as separate retro fit devices, it will be appreciated that similar embodiments can be implemented if heat generating components and cooling apparatus are integrally formed. Hence, it can be seen that an arrangement is provided in which cooling can be provided at extremely low cost in a highly reliable modular manner and which does not affect normal operation of heat generating component deployments. Such arrangements do not significantly affect safety of heat generating components, or require high maintenance, unlike standard solutions which enclose the heat generating components thereby promoting the possibility of catastrophic failure due to heat.

Figure 7 is an exploded perspective view of an alternative temperature management system 700 of the invention and an array (stack) 750 of heat generating components which in the array are a series of telecommunications devices 701 . The array 750 is held in place/supported by vertical support members 702, and in the embodiment with one at each of four corners of the array 750. As can be seen from the Figures the telecoms devices 701 are closely fitted components and are thus susceptible to overheating within the array. Figure 8 is a perspective view from the front and to one side of the alternative temperature management system 700 as shown in Figure 7; while Figure 9 is a perspective view of the temperature management system 700of Figure 7 inserted into the array (stack) 750. The thermal management system or device 700 comprises a carrier which in the embodiment takes the form of a vertical support plate 720. To the support plate 720 is mounted a heat dissipating element in the form of a series of heating fins 710 and a series of heat pipes 730. Mounted between the heat fins 710 and the heat pipes 730 are thermoelectric modules 71 1 . As can be seen the heat pipes 730 provide a plurality of thermally conductive structures projecting as fingers from the carrier and arranged to provide a plurality of thermal paths. It will be appreciated that the device 700 can provide multiple cooling points which may be proximate one piece of equipment, or a plurality of pieces of equipment, or some combination thereof. The heat pipes operate in the same manner as described above, for example as described in relation to Figure 1 above. It will be appreciated that this embodiment demonstrates a concept which allows the insertion of the thermal management system between components in a vertically stacked system. Earlier embodiments showed the thermal management system in use between horizontally spaced apart components. The support plate 720 is in turn coupleable to the vertical support members 702 of the array 750, by means of brackets 725 and connecting pieces 726. This is best seen in Figures 8 and 9. Figure 8 shows the assembled device 700. It is ready for attachment to an insertion into the array 750. Figure 9 shows the device 700 inserted into the array. In effect the device 700 runs on a rail and is thus easily insertable and removable from the array 750.

When inserted fully substantially only the heat fins 710 protrude to an extent from the array 750 thus allowing for external heat dissipation. It will be appreciated that spreader plates etc. as mentioned for the embodiment above may also be used with the device of the invention. For example one or more horizontal spreader plates may be used.

Furthermore it will be appreciated that the concept of using a carrier for the thermoelectric modules and the heat pipes is a versatile concept. For example the number and spacing of the heat pipes can be varied. The carrier is easily adapted for fitting to different arrays. Furthermore the device can be adapted for the array to which it is fitted for example by providing suitable connection points etc. The description and drawings merely illustrate the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its scope. Furthermore, all examples recited herein are principally intended to expressly be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.