Abstract:
A system for controlling thermal conductivity between two thermal masses is disclosed. The system includes a first conduction body in thermal contact with a heat source and a second conduction body in contact with a heat sink. A thermal expansion component operatively connects to the first conduction body and moves the body between first and second positions at a predetermined temperature. In the first position the first conduction body is spaced apart from the second conduction body, thermally isolating the heat source from the heat sink. In the second position the first conduction body thermally contacts the second conduction body, and conducts heat from the heat source, through the conduction bodies and into the heat sink. Related methods are also described.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to thermal conductivity control devices, and more particularly, to thermal conductivity control devices that reduce the heat transfer rate from a heat source to a heat sink below a predetermined temperature. 
         [0003]    2. Description of Related Art 
         [0004]    Vehicles rely on batteries for power when power is not available from onboard electrical generators or an external source. Typically, vehicles have used conventional batteries with lead-acid cells or nickel-cadmium cells to meet onboard power needs when onboard generators and external sources are not available. Developments in vehicle systems have led to greater power requirements, and vehicle designers have therefore turned to high energy chemistry batteries for vehicular power storage. Lithium metal and lithium ion chemistry batteries, such as lithium cobalt oxide, have gained widespread acceptance in vehicular applications owing to their relatively small size and weight for a given amount of power storage. High energy chemistry batteries are desirable in automotive and aerospace applications because of their high energy density relative to conventional battery chemistries, such as nickel cadmium or lead acid chemistries. 
         [0005]    High energy batteries generate power through an exothermic reaction. The heat generated by the exothermic reaction needs to be dissipated from the battery. Vehicles therefore typically include a thermally efficient conduit coupling the battery to the environment external to the vehicle to dissipate heat while the battery is in operation. High energy batteries can also have a minimum operating temperature below which battery performance degrades. They therefore rely on internally generated heat or a battery powered external heating element to maintain the temperature of the battery above a minimum operating temperature. However, under certain conditions, the highly efficient conduit used to cool the battery during operation also dissipates heat generated to keep the battery above its minimum operating temperature, thereby reducing available battery power and/or reducing battery life. Vehicles operating in cold ambient temperature environments are particularly susceptible to this problem. 
         [0006]    Conventional methods and system for battery cooling have generally been considered satisfactory for their intended purpose. However, there is a need in the art for a thermal conductivity control device capable of reducing conduction path effectiveness during operation in cold ambient temperature environments. There is a further need for controlling thermal conductivity effectiveness in cold ambient temperature environments that is easy to make and use, and readily adaptable for use in existing battery installations. The present invention provides a solution for at least one of these needs. 
       SUMMARY OF THE INVENTION 
       [0007]    The subject invention is directed to a new and useful system for controlling thermal conductivity between two thermal masses. The system includes a first conduction body configured and adapted for thermal contact with a heat source and a second conduction body configured and adapted for thermal contact with a heat sink. The system also includes a thermal expansion component operatively connected to move the first conduction body between a first position in which the first conduction body is spaced apart from the second conduction body for thermal isolation of the heat source and heat sink, and a second position in which the first conduction body is in thermal contact with the second conduction body for conduction of heat from the heat source, through the conduction bodies, and into the heat sink. The thermal expansion component is configured and adapted to move the first conduction body into the second position at a predetermined temperature. 
         [0008]    In certain embodiments the first and second positions of the first conduction body define a direction of motion of the first conduction body with respect to the second conduction body. The conduction bodies can also have a wedge face oblique with respect to the direction of motion of the first conduction body. The wedge faces of conduction bodies can oppose one another, and in certain embodiments, can define an insulating gap between the bodies when the first conduction body is in its first position. The wedge faces can further form a thermally conductive interface when the first conduction body is in its second position. In an embodiment, at least one of the wedge faces is smooth and can be a polished surface for example. 
         [0009]    In certain embodiments the thermal expansion component can include a cylinder configured to remain stationary relative to the second conduction body. A piston body operatively connects the first conduction body to the cylinder. The thermal expansion component can also include a thermal expansion body within the cylinder. The thermal expansion body is disposed between the cylinder and the piston, and upon reaching a predetermined temperature, expands to drive the first conduction body in the direction of motion from its first position to its second position. The thermal expansion body can further apply pressure to the opposing wedge faces defining the interface in the second position. The thermal expansion body can be a paraffin wax pellet, for example. 
         [0010]    In accordance with certain embodiments the system can also include a resilient member that biases the first conduction body towards the first position. The resilient member can include a spring fixed on a first end to the cylinder and fixed to the piston on another end, for example. The invention also provides a battery system. The system includes a battery body for storing and supplying electrical energy, a first conduction body in thermal contact with the battery body, and a thermal expansion component. The thermal expansion component operatively connects to the first conduction body and moves the first conduction body between a first position and a second position at a predetermined temperature. In the first position the first conduction body is spaced apart from a second conduction body, and thermally isolating the battery body from a heat sink in thermal contact with the second conduction body. In the second position the first conduction body thermally contacts the second conduction body and conducts heat from the battery body, through the conduction bodies, and into the heat sink. In certain embodiments the heat sink is thermally communicative with an exterior of an aircraft or an aircraft fuel reservoir. 
         [0011]    The invention also provides a method for controlling thermal conductivity between thermal masses. The method includes contacting a heat source with a first conduction body, contacting a heat sink with a second conduction body, and conducting heat between the heat source and heat sink through the conduction bodies by thermally contacting the second conduction body with the first conduction body. First and second are placed into thermal contact by operation of a thermal expansion component, which moves the first conduction body between first and second positions at a predetermined temperature. 
         [0012]    In an embodiment, the method also includes compressing the first conduction body against second conduction body, thereby increasing a rate of heat transfer between the heat source and the heat sink. In an exemplary embodiment, placing the bodies into thermal contact additionally includes sensing temperature of the heat source with the thermal expansion component, such as by volumetrically expanding a thermal expansion body captive within the thermal expansion component. 
         [0013]    These and other features of the systems and methods of the subject invention will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    So that those skilled in the art to which the subject invention appertains will readily understand how to make and use the devices and methods of the subject invention without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
           [0015]      FIG. 1  is a schematic cross-sectional elevation view of an exemplary embodiment of a thermal conductivity control system constructed in accordance with the invention; 
           [0016]      FIGS. 2A-2F  are schematic cross-sectional elevation views of the thermal conductivity control device of  FIG. 1 , respectively showing a sequence of operational position; and 
           [0017]      FIG. 3A   FIG. 3B  are schematic cross-sectional elevation views of another exemplary embodiment of a thermal conductivity control system constructed in accordance with the invention, showing operation of the thermal expansion component of the system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject invention. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of the thermal conductivity control system in accordance with the invention is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments of the thermal conductivity system in accordance with the invention, or aspects thereof, are provided in  FIG. 2  and  FIG. 3 , as will be described. System  100  can be used for dissipating heat from high energy power storage devices, for example, and in vehicles operated in cold ambient temperature environments. 
         [0019]    Referring now to  FIG. 1 , a thermal conductivity control system  100  is shown. Thermal conductivity control system  100  has a first conduction body  110  and a second conduction body  120 . First conduction body  110  is slideably disposed on a surface of a first thermal element  102 . Second conduction body  120  is fixed to a surface  124  of a second thermal element  104 . In an embodiment, first thermal element  102  is a heat source and second thermal element  104  is a heat sink. For example, first thermal element  102  can be a battery and second thermal element can be a heat sink thermally communicative with an aircraft exterior. 
         [0020]    First conduction body  110  defines a wedge face  112 , a source face  114  adjacent wedge face  112 , and a distal face  116  adjacent to wedge face  112  and to source face  114 . First conduction body  110  is slideably disposed on surface  108  of first thermal body  102  along a portion of source face  114 . System  100  can also include a thermally conductive lubricant disposed between the source face  114  and surface  108 , thereby reducing friction between face  114  and surface  106  and providing thermal coupling during movement of face  114  across surface  106 . 
         [0021]    Second conduction body  120  has a wedge face  122  opposite wedge face  112  of first conduction body  110 , a sink face  124  adjacent to wedge face  122 , and a distal face  126  adjacent to wedge face  122  and sink face  124 . Sink face  124  is configured and arranged to conduct heat into second thermal mass  104 , thereby transferring heat from second conduction body  120 . First and second conduction bodies  110  and  120  define a movement axis  106 , shown in  FIG. 1  extending to the right in the figure, axis  106  being substantially parallel to surface  108 . In an exemplary embodiment, first and second conduction bodies  110  and  120  are constructed from a material with a high heat transfer coefficient such as copper or aluminum. 
         [0022]    Oppositely disposed wedge faces  112  and  122  are substantially parallel to one another, and define a gap  130  therebetween. Gap  130  extends between first and second conduction bodies  110  and  120  and has a width  132 . Gap width  132  extends orthogonally with respect to surfaces defined by wedge faces  112  and  122 , and defines an insulating barrier between first and second conduction bodies  110  and  120 . Gap  130  reduces the efficiency of a thermal conduit defined by first and second conduction bodies  110  and  120  such that heat transfers between bodies  110  and  120  is greatly reduced in the first position with gap  130  at a maximum. Gap  130  can be an evacuated space, an air gap, or an insulating fluid-filled reservoir. As will be appreciated, the thermal effectiveness of the conduction conduit defined by bodies  110  and  120  is influenced by both gap width  132  and the material (if any) disposed within gap  130 . 
         [0023]    With further reference to  FIG. 1 , system  100  also includes a thermal expansion component  140 . Thermal expansion component  140  includes a fixed element  142  and a movable element  144 . Thermal expansion component  140  is in thermal communication with heat source  102  and is operably coupled to first conduction body  110  at distal face  116 . Movable element  144  extends from fixed element  142  in the direction of a movement axis  106 , and can vary in connecting length based on the temperature of thermal expansion component  140 . Movement axis  106  defines a direction of movement of first conduction body  110  with respect to second conduction body  120 , and wedge faces  112  and  122  are oblique with respect to movement axis  106 . Component  140  is operable to displace first conduction body  110  by sliding body  110  across first thermal body  102  in the direction of movement axis  106 . Second conduction body  120  is fixed with respect to movable element  144 , so displacement of first conduction body  110  by movable element  144  changes the positional relationship between wedge faces  112  and  122  by increasing or decreasing gap width  132 . As will be appreciated, other arrangements of conduction bodies  110  and  120  and thermal expansion component  140  are within the scope of the present invention. For example, first conduction body  110  may be fixed to first thermal body  102 , and second conduction body  120  may be operably coupled to thermal expansion component  140  so as to slide across a surface of second thermal body  104 . Alternatively, each of first and second conduction bodies  110  and  120  may be movable with respect to thermal bodies  102  and  104 , and one or more thermal expansion components  140  can be operably coupled to both body  110  and  120 . 
         [0024]    Referring now to  FIGS. 2A-2F , system  100  is shown in a sequence of configurations in accordance with the present invention. Referring to  FIG. 2A , first conduction body  110  is shown in position (i). In position (i), gap  130  has a width (i) and conduction bodies  110  and  120  define a thermal conduit with a heat transfer coefficient (i). In the illustrated configuration first and second bodies  110  and  120  define a low efficiency thermal conduit that allows substantially no conductive heat transfer across gap  130 . 
         [0025]    Referring to  FIG. 2B , first conduction body  110  is shown in position (ii). First conduction body  110  moves from position (i) to position (ii) by operation of thermal expansion component  140 , component  140  displacing conduction body  110  by applying a force A to the distal face  116  of body  110 . Force A displaces first conduction body  110  across surface  108  of first thermal body  110  by pushing body  110  toward body  120  along movement axis  106 . Force A urges first conduction body  110  across surface  108  of first thermal body  110 , displacing body  110  from position (i) to position (ii) and narrowing gap  130 . In the illustrated configuration, gap  130  has a width (ii) and conduction bodies  110  and  120  define a thermal conduit with a heat transfer coefficient of (ii). Width (ii) is smaller than width (i) and heat transfer coefficient (ii) is substantially equal to heat transfer coefficient (i). 
         [0026]    Referring to  FIG. 2C , first conduction body  110  is shown in position (iii). Body  110  moves from position (ii) to position (iii) from continued application of force on first conduction body  110  by thermal expansion component  140 , as described above. Thermal expansion component  140  moves the first conduction body into position (iii) at a predetermined temperature. In position (iii), displacement of body  110  causes wedge faces  112  and  122  to come into thermal contact, thereby eliminating gap  130  with a mechanical interface  134  extending between bodies  110  and  120 . First conduction body  110 , interface  134 , and second conduction body  120  define a thermally efficient conduit with a heat transfer coefficient of (iii) that allows a flow of heat AA to move across the conduit. In the illustrated embodiment, heat transfer coefficient (iii) is greater than heat transfer coefficients (i) and (ii). In an exemplary embodiment, heat transfer coefficient (iii) is smaller than the heat transfer coefficient of the material(s) from which bodies  110  and  120  are constructed due to the thermal contact resistance across interface  134 . 
         [0027]    Referring to  FIG. 2D , first conduction body  110  is shown in position (iv). Position (iv) is similar to position (iii), and additionally includes compressive forces  136  and  138  applied at the respective wedge faces. Thermal expansion component  140  can optionally apply additional force on first conduction body  110  in position (ii), thereby urging wedge face  112  against wedge face  122 . Since wedge face  122  is fixed, force A presses wedge face  112  against wedge face  122 , inducing a compressive force  136  on face  112  and compressive force  138  on wedge face  122 . Compressive forces  136  and  138  cause interface  134  to conduct heat relatively efficiently, and render system  100  a more effective heat conduit. The heat transfer conduit defined by first and second conduction bodies  110  and  120  therefore has a heat transfer coefficient (iv) that is greater than heat transfer coefficient (iii). Thermal expansion component  140  moves the first conduction body  110  into configuration (iv) at a predetermined temperature. In the illustrated embodiment, coefficient (iv) approaches that of the material(s) from which first and second conduction bodies  110  and  120  are constructed. Wedge faces  112  and  122  can be polished or lapped surfaces, thereby facilitating heat transfer across the faces when in contact with one another. 
         [0028]    Referring to  FIG. 2E , first conduction body  110  is shown in position (v). Position (v) is similar to positions (iii) and (iv) absent the application of compressive forces on the opposed wedge faces. Wedge faces  112  and  122  remain in mechanical contact but no longer exert compressive forces on the opposing faces. First and second conduction bodies  110  and  120  define a heat transfer conduit with a heat transfer coefficient (v). In the illustrated embodiment, heat transfer coefficient (v) is substantially the same as heat transfer coefficient (iii). 
         [0029]    Referring to  FIG. 2F , first conduction body  110  is in a position (vi). First conduction body  110  moves from position (v) to position (vi) by operation of thermal expansion component  140 , component  140  displacing conduction body  110  by applying a force B to the distal face  116  of body  110 . Force B displaces first conduction body  110  across first thermal body  110  by pulling body  110  toward component  140  along movement axis  106 . Displacement of body  110  from position (v) to position (vi) isolates wedge face  112  from wedge face  122  by re-establishing gap  130 . Gap  130  renders the heat transfer conduit defined by first and second conduction bodies  110  and  120  less effective than that of position (v). In the illustrated configuration bodies  110  and  120  define a heat transfer coefficient (vi) that is substantially equal to above-described heat transfer coefficient (i and ii). As will be appreciated, heat can transfer both by conduction and radiation. Embodiments described herein greater amounts of heat by conduction than by radiation at common ambient temperatures, such as below 120° Fahrenheit for example. At greater temperatures a larger amount of heat can be transferred by radiation than by conduction. 
         [0030]    Operatively, system  100  controls thermal conductivity between thermal bodies  102  and  104  by (a) thermally contacting first conduction body  110  with thermal body  102 ; (b) thermally contacting second conduction body  120  with thermal body  104 ; (c) thermally contacting second conduction body  120  with first conduction body  110  by moving body  110  between a first position using thermal expansion component  140 ; and (d) conducting heat from thermal body  102  to thermal body  104  across bodies  110  and  120 . As will be appreciated, first body  102  can be a heat source and second body  104  can be a heat sink. As will also be appreciated, first position can be as illustrated in  FIG. 2A  or  FIG. 2B  and second position can be as illustrated in  FIG. 2C  or  FIG. 2D . As will additionally be appreciated, conducting heat can be as illustrated in  FIG. 2C ,  FIG. 2D , or  FIG. 2E . The method can optionally include (e) compressing first conduction body against second conduction body, thereby increasing a rate of heat transfer between the heat source and the heat sink. Advantageously, embodiments of the method wherein further pressure is applied across positionally fixed bodies  110  and  120  increases heat transfer across the bodies owing to opposing compressive forces applied at the contacting faces of the bodies. 
         [0031]    Thermal expansion component  140  thermally moves bodies  110  and  120  upon reaching a predetermined temperature, as described above. Component  140  can operate by volumetrically expanding a thermal expansion body captive within component  140 , such as a wax ball or like element that undergoes a significant volumetric expansion, e.g. about a 10% volumetric expansion, in response to temperature change. As will be appreciated, a phase change may accompany the volumetric expansion, such as from solid to liquid, liquid to gas, or solid to gas. Alternatively, component  140  can be operable through a thermal expansion component that changes shape as result of thermal expansion, such a bimetal plate that exhibits a greater amount of bow at a predetermined temperature. The bowing of such a bimetal plate would operate to drive first conduction body axially, along axis  106 , at the predetermined temperature. The bimetal plate can be a snap disk, for example. 
         [0032]    Referring now to  FIG. 3A , a battery system  200  with a first conduction body in a first position. System  200  includes a first conduction body  210 , a second conduction body  220 , and a thermal expansion component  240 . First and second conduction bodies  210  and  220  are similar to bodies  110  and  120  described above, first conduction body  210  being in thermal contact with a battery body  202  and second conduction body  220  being in thermal contact with a heat sink  204 . Battery body  220  is configured for storing and supplying electrical power to a vehicle, such as an automobile or an aircraft. 
         [0033]    Thermal expansion component  240  is similar to above-described thermal expansion component  140 , and is as additionally described below. Thermal component  240  is in thermal contact with battery body  202  such that temperature change within battery body  202  induces corresponding temperature change in thermal component  240 . Thermal component  240  includes a fixed element  242 , a movable element  244 , and a return element  246 . 
         [0034]    Fixed element  242  of thermal component  240  is a cylinder with an interior surface  248  and an aperture  254 . On its distal end, a portion of the cylinder interior surface  248  defines a chamber  252 . On its proximate end, cylinder  242  has an aperture  254  defining an avenue to chamber  252 . A portion of return element  246  is fixedly coupled to cylinder  242 , and cylinder  242  is in thermal contact with battery body  202 . Cylinder  242  can be mechanical coupled to battery body  202  by any suitable means such as screws, clamps or fasteners for purpose of providing access to battery body  202  for servicing and/or replacement as appropriate. 
         [0035]    Movable component  244  of thermal component  240  is a piston body defining a piston face on a distal end and coupling element on its proximate end. The proximate end of piston  244  operably couples first conduction body  210  and can be any suitable coupling, for example rigid or flexible, such that translation (displacement) of piston  244  along movement axis  206  induces corresponding translation (displacement) of first conduction body  210  along movement axis  206 . The piston face of the distal end of piston body  244  cooperates with a portion of cylinder interior  248  to define chamber  252 . As would be appreciated, translation of piston body  244  change volume comprised by chamber  252 , and volume change of chamber  252  induces translation (displacement) of piston body  244 . 
         [0036]    Return element  246  of thermal component  240  includes a distal post  256 , a proximate post  258 , and a resilient member  260  extending distal and proximate posts  256  and  258 . Distal post  256  is fixedly coupled to cylinder  242 . Proximate post  258  is fixedly coupled to first conduction body  210 . Resilient member  260  can be a spring operable to exert a force when extended beyond a predetermined length. As will be appreciated, resilient member  260  is operable to bias first conduction body  210  in distally, thereby urging conduction body  210  towards a first position wherein first conduction body  210  is not in thermal contact with second conduction body  220 . As will also be appreciated, other resilient member types and arrangement are possible and with the scope of the invention. For example, resilient member  260  may be spring wound about the periphery of piston  244 . 
         [0037]    With further reference to  FIG. 3A , a thermal expansion body  262  is captive within chamber  252  and in thermal communication with cylinder  242 . As illustrated in  FIG. 3A , body  262  has a pellet shape. This is for illustrative purposes and non-limiting. Thermal expansion body  262  is a deformable mass in contact with both the portion of cylinder interior  248  defining chamber  252  and the face of piston body  244 , and occupies substantially all of the volume of chamber  252 . Thermal expansion body  262  further defines the volume of chamber  252 , and is constructed of a material that exhibits a significant volumetric expansion at a predetermined temperature, such as paraffin wax for example. Below a predetermined temperature, thermal expansion body  246  defines a first volume of chamber  252 . Above the predetermined temperature, thermal expansion body  246  undergoes volumetric expansion, thereby defining a second volume of chamber  252 , the second volume being greater than the first volume. In an embodiment, volumetric expansion includes a phase change of the material from which body  262  is constructed, such as from solid to liquid or liquid to gas. As will be appreciated, further temperature increases above the predetermined temperature can cause corresponding increase of the chamber volume defined by thermal expansion body  246 . Similarly, further temperature decreases below the predetermined temperature can cause corresponding decrease of the chamber volume defined by thermal expansion body  246 . Moreover, as piston body  244  is operable coupled to first conduction body  210  on its proximate end, changes in the volume of chamber  252  operate to displace first conduction body  210  along movement axis  206 . 
         [0038]    The temperature of battery body  202  influences the position of first conduction body  210  and the position of first conduction body influences the temperature of battery body  202 . More specifically, thermal contact of battery body  202  with cylinder  246  causes temperature change in battery body  202  to induce corresponding temperature change in cylinder  246 . Thermal contact of cylinder  246  with thermal expansion body  262  in turn causes temperature change of cylinder  246  to induce corresponding temperature change in thermal expansion body  262 . When the temperature of thermal expansion body  262  rises above a predetermined temperature, its mass volumetrically expands, thereby urging piston body  244  proximately. Expansion of thermal expansion body  262  can apply proximately directed force that exceeds the biasing force of resilient member  260 , at which point thermal expansion body  262  both axially displaces piston body  244  and first conduction body  210  along movement axis  206  and extends resilient member  260 . As will appreciated, second conduction body  220  can be arranged along movement axis  206  such that thermal expansion body  262  places first conduction body  210  in thermal contact with second conduction body  220  at and above the predetermined temperature. 
         [0039]    Referring now to  FIG. 3B , system  200  is shown with first conduction body  210  in a second position. In the second position first conduction body  210  is in thermal contact with second conduction body  220 , and a heat transfer flow AA transfers thermal energy from battery body  202 , into first conduction body  210 , across an interface  234  between bodies  210  and  220 , into second conduction body  220 , and thereafter into heat sink  204 . Heat sink  204  can thereafter dissipate heat into the environment external a vehicle housing battery body  202 . As will be appreciated, heat flow AA can reduce the temperature of battery body  202  such that the temperature of thermal expansion body  262  drops below the predetermined body, thereby causing the volume of thermal expansion body  262  to decrease and reducing the force applied to the face of piston body  244 . Once the force applied to the piston face drops below the level of the biasing force of resilient member  260 , resilient member  260  displaces piston body  244  and first conduction body distally, thereby translating piston body  244  and first conduction body  210  axially along movement axis  206 . This displacement spaces first conduction body  210  apart from second conduction body  220 , thereby thermally isolating battery body  202  from heat sink  204 . 
         [0040]    As will appreciated, system  200  can alternatively cycle between first and second positions as dictated by the temperature adopted by battery body  202  owing to its operation and/or the temperature environment within which the vehicle housing battery body  202  is operated. As will also be appreciated, since the thermal body is a passive actuator, embodiments of the control device described herein do not rely upon other systems for their operation. 
         [0041]    The methods and systems of the present invention, as described above and shown in the drawings, provide for thermal conductivity control with superior properties including control of heat path efficiency of a heat conduit connecting a battery body to an environment external to a vehicle housing the battery body. While the apparatus and methods of the subject invention have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject invention.