Patent Publication Number: US-2020292048-A1

Title: Non-metal sprocket with reduced thermal expansion

Description:
RELATED APPLICATION INFORMATION 
     This Patent Application is a continuation in part of, and claims priority to, U.S. Non-provisional patent application Ser. No. 16/307,950, filed Dec. 7, 2018, the disclosure of which is incorporated herein in its entirety, by reference. 
    
    
     FIELD 
     The field to which the disclosure generally relates is belt sprockets, and more particularly to belt sprockets formed from polymeric materials which are usable with standard bushings. 
     BACKGROUND 
     This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art. 
     Sprockets typically include a plurality of teeth that are arranged in alternating fashion with groves. The teeth and grooves extend about an entire outer circumference of the sprocket. A toothed belt engages the toothed surface. Conventional sprockets for high torque applications are made of iron or steel. Often the sprocket is affixed onto a shaft with a bushing. The use of a bushing allows a sprocket to be installed on many different shaft sizes. Two common types of bushings are quick disconnect (QD) and Taper-Lock. Both of these bushing types use a tapered interface between the sprocket hub and bushing which generates large hub forces in the sprocket in order to clamp onto the shaft. 
     Synchronous belts and pulleys are commonly offered in standard pitch sizes of 5, 8, 14, and 20 mm. There are some offerings of non-metal pulleys in the 5 and 8 mm pitch sizes. These are typically made of nylon molded to an aluminum or steel hub with a straight bore and set screw for attaching to a shaft. However, such pulleys are not adequately durable for high torque applications, many of which require the larger pitch sizes. 
     In some cases, synchronous pulleys made of other materials than steel can have wear issues and have the teeth erode, wear out and fail. Thus, there is an ongoing need for durable non-metal pulleys or sprockets for high torque applications, such need is met, at least in part, with embodiments according to the following disclosure. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a necessarily a comprehensive disclosure of its full scope or all of its features. 
     In a first aspect of the disclosure, a high torque sprocket is provided which includes a body defining an outer periphery and a hub section defining an inner surface for engaging a bushing. A continuous toothed structure is disposed on the outer periphery of the body, and a textile reinforcement embedded in the body adjacent the inner surface of the hub section. The body is formed of a castable polymer material, such as a polyurethane material, epoxy material, or the like. In some cases, one or two optional flanges are disposed on side(s) of the body immediately adjacent the continuous toothed structure, and in some further aspects, a textile reinforcement may be embedded in a surface of the flange(s) immediately adjacent the continuous toothed structure. The hub section inner surface may be of a tapered shape, and maybe adapted to engage a conventional QD bushing or a taper-lock bushing. In some applications, the high torque sprocket may be used as a synchronous sprocket, gear sprocket, or coupling. Also, the sprockets may include any other features or materials described in the summary or the description. 
     In some aspects, the high torque sprockets further include a textile reinforcement embedded in the continuous toothed structure outer surface, and the textile reinforcement is selected from nylon, carbon cordage, cotton, aramid, PTFE, and mixtures thereof. 
     In some aspects, the high torque sprockets have a castable polymer material body devoid of any metal structure, and may further define ports which could have threaded metal inserts placed therein. In some embodiments, the continuous toothed structure is formed of steel or the castable polymer material. 
     In some other embodiments of the disclosure, high torque sprockets include a body defining an outer periphery and a hub section for engaging a bushing, and a belt engaging structure disposed on the outer periphery of the body. The hub section inner surface is a tapered shape, and the body is formed of a castable polymer material which is devoid of any metal structure. A textile reinforcement may be embedded in the body adjacent the hub section inner surface. The high torque sprockets may further include a flange, or flanges, disposed on a side, or sides, of the body immediately adjacent the belt engaging structure. In some cases, a textile reinforcement is embedded in a surface of the flange(s) immediately adjacent the belt engaging structure. Also, a textile reinforcement may be embedded in the belt engaging structure outer surface. The textile reinforcements may be selected from carbon cordage, nylon, cotton, aramid, PTFE, and mixtures thereof. The hub section inner surface is adapted to engage a conventional QD bushing or a taper-lock bushing. The high torque sprockets may be used for engaging a v-belt, poly v-belt, micro v-belt, or synchronous belt. Also, the sprockets may include any other features or materials described in the summary or the description. 
     Yet other embodiments of the disclosure are high torque sprockets having a body defining an outer periphery and a hub section for engaging a bushing, a continuous toothed structure disposed on the outer periphery of the body, and a textile reinforcement embedded in the hub section inner surface. The hub section inner surface is a tapered shape. An outer portion of the body is formed of a castable polymer material and an inner portion of the body is formed of steel. In some aspects, the castable polymer material is adhered to the inner portion of the body using a precoating, while in some other aspects, the castable polymer material is cast onto the inner portion of the body. Further, the sprockets may include any other features or materials described in the summary or the description. 
     In some embodiments of the disclosure, the castable polymer material contains ultra-high molecular weight polyethylene (UHMWPE) powder in a suitable amount to provide increased durability to the sprocket. In some cases, the average size of the particles in the UHMWPE powder may be from about 20 microns to about 100 microns, from about 40 microns to about 80 microns, or even from about 50 microns to about 70 microns. The UHMWPE powder may be incorporated in suitable amounts, such as from about 1% to about 10% by weight of the castable polymer material, from about 2% to about 8% by weight of the castable polymer material, or even from about 3% to about 7% by weight of the castable polymer material. 
     In some cases, the addition of the UHMWPE powder imparts increases the hardness of the final cured castable polymer material mixture to from about 60 Shore D to about 100 Shore D hardness value, or even from about 75 Shore D to about 85 Shore D hardness value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain embodiments of the disclosure will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements. It should be understood, however, that the accompanying figures illustrate the various implementations described herein and are not meant to limit the scope of various technologies described herein, and: 
         FIG. 1  illustrates a high torque sprocket in a perspective view, according to an embodiment of the disclosure; 
         FIGS. 2A and 2B  together depict in an isometric view, other aspects of some high torque sprockets according to embodiments of the disclosure; 
         FIGS. 3A-3D  show in side views, some examples of continuous toothed or grooved patterns useful in sprockets according to the disclosure; and 
         FIG. 4  depicts a high torque sprocket and bushing assembly in a perspective view, according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of the variations is merely illustrative in nature and is in no way intended to limit the scope of the disclosure, its application, or uses. The description and examples are presented herein solely for the purpose of illustrating the various embodiments of the disclosure and should not be construed as a limitation to the scope and applicability of the disclosure. While the compositions of the present disclosure are described herein as comprising certain materials, it should be understood that the composition could optionally comprise two or more chemically different materials. In addition, the composition can also comprise some components other than the ones already cited. In the summary of the disclosure and this detailed description, each numerical value should be read once as modified by the term “about” (unless already expressly so modified), and then read again as not so modified unless otherwise indicated in context. Also, in the summary of the disclosure and this detailed description, it should be understood that a concentration or amount range or dimension listed or described as being useful, suitable, or the like, is intended that any and every concentration or amount or dimension within the range, including the end points, is to be considered as having been stated. For example, “a range of from 1 to 10” is to be read as indicating each and every possible number along the continuum between about 1 and about 10. Thus, even if specific data points within the range, or even no data points within the range, are explicitly identified or refer to only a few specific, it is to be understood that inventors appreciate and understand that any and all data points within the range are to be considered to have been specified, and that inventors had possession of the entire range and all points within the range. 
     Unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by anyone of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present). 
     In addition, use of the “a” or “an” are employed to describe elements and components of the embodiments herein. This is done merely for convenience and to give a general sense of concepts according to the disclosure. This description should be read to include one or at least one and the singular also includes the plural unless otherwise stated. 
     The terminology and phraseology used herein is for descriptive purposes and should not be construed as limiting in scope. Language such as “including,” “comprising,” “having,” “containing,” or “involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited. 
     Also, as used herein any references to “one embodiment” or “an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily referring to the same embodiment. 
     In some embodiments, a high torque sprocket  100 , as depicted in the perspective view presented in  FIG. 1 , is provided which includes a body  102  defining an outer periphery  104 , and a hub section  106  for engaging a bushing. A continuous toothed structure  108  is disposed completely around the outer periphery of the body  102 . In some embodiments, a textile reinforcement is embedded in the hub section adjacent inner surface  110 . The textile reinforcement may embedded adjacent inner surface  110  at any suitable distance from inner surface  110 , so that it may provide effective shape maintaining strength to the overall body  102  from hoop stresses imparted onto body  102  when a bushing is installed into hub section  106 . 
     The body  102  may be formed of a castable polymer material, and in some aspects, may be essentially free or devoid of any metal structure, or structures. In some other aspects, the body  102  is formed of a castable polymer material, and includes a metal hub upon which the castable polymer body  102  is adhered to, cast upon, or otherwise installed upon. In some other embodiments, the body  102  is formed of a castable polymer material essentially free or devoid of any metal structure(s) other than metallic threaded inserts and/or metallic collars installed within ports of the body  102  for retaining an installed bushing; and in such cases, it is within the definition of “essentially free or devoid of any metal structure(s)” when such separate metallic parts are installed into one or more ports, or even partial ports, as described in further detail below. 
     In some embodiments, the continuous toothed structure  108  disposed around the outer periphery of body  102  is an extension of, or otherwise formed from, the castable material forming body  102 . In such cases, the matrix of material forming body  102  and toothed structure  108  is essentially a continuous matrix, and even so in cases where suitable textile reinforcement material(s) are embedded therein. In some alternative embodiments, the continuous toothed structure  108  disposed around the outer periphery of body  102  is formed a different material from the castable material forming body  102 , such as a different polymeric material or composite, or even metal, such as steel, aluminum, and the like. Also, optionally, in some embodiments, an outer portion of the body  102  is formed of the castable polymer material and an inner portion of the body is formed of steel,  122 , as alternatively illustrated in  FIG. 1 . 
     In some aspects, a flange  112  is disposed on a side of the body  102  immediately adjacent the continuous toothed structure  108 . Although one flange is shown in the embodiment illustrated in  FIG. 1 , it is within the scope of the disclosure that sprocket embodiments have zero, one or two flanges. In some embodiments, a textile reinforcement is embedded in the side surface  114  of the flange  112  (or flanges when two are used) immediately adjacent the continuous toothed structure  108 . Also, in some embodiments, a textile reinforcement is embedded in the continuous toothed structure  108  outer surface. As further shown in  FIG. 1 , body  102  may include ports  116 ,  118  formed therein for such purposes as attachment to other components with suitable fasteners for retaining a bushing, balance, weight optimization, temperature conductivity, and the like. 
     Now referencing  FIGS. 2A and 2B , which depict other aspects of some sprocket embodiments according to the disclosure. Sprocket  200  is shown in  FIG. 2A  from a side view perspective, and includes body  202 . Continuous toothed structure  204  is disposed completely around the outer tooth periphery  206  of the body  202 . Optional flanges  208  and  210  extend outwardly from the outer edges of tooth periphery  206 , and while two flanges are shown, it is within the scope and spirit of the disclosure to have one flange, such as  208  or  210 , or no flange, as well. Body  202  further defines hub section  212 , which is essentially an opening for accepting and engaging a bushing. As shown in  FIG. 2B , a cross-sectional view of  FIG. 2A  taken at section A, hub section  212  is a tapered shape where the diameter of opening  214  is greater than the diameter of opening  216 . Body  202  may further define ports  218  (three shown, for example, in  FIG. 2A ) for securing or otherwise retaining the sprocket onto a QD type bushing using a suitable fastener system. 
     As further depicted in  FIG. 2B , the high torque sprocket further includes at least one high modulus tensile member  220  (5 shown) disposed beneath and/or upon the periphery of the body, and below the continuous toothed structure. The high modulus tensile member(s)  220  may be helically or linearly wrapped upon or within the body in the circumferential direction of the sprocket. Any suitable number of high modulus tensile members  220  may be used, such as 1, 2, or even from 3 to about 50. 
     While most industrial sprockets are made from metal, such as cast iron, the sprockets according this disclosure are based upon a castable polymer material. Sprockets made from metal typically have a thermal coefficient of expansion of approximately 11×10 −6 /deg Celsius, providing acceptable amount of dimensional change of typical operating temperature. Also, sprockets made from metal typically have a mass of about 45 kg or greater. Thus, sprockets according this disclosure are significantly lower in mass, below 45 kg, and have a thermal coefficient of expansion of from about 7×10 −6 /deg Celsius to about 14×10 −6 /deg Celsius, such as approximately 10×10 −6 /deg Celsius, or even approximately 11×10 −6 /deg Celsius, over an operating temperature of from about −35 deg Celcius to about 60 deg Celcius. This is a significant reduction from typical castable polymer material thermal coefficient of expansion of about 108×10 −6 /deg Celsius. 
     In some embodiments, the one or more high modulus tensile members  220  are applied onto the circumferential periphery of the body, or within the body near the circumferential periphery, before sprocket teeth are molded on the sprocket. According to one aspect of the disclosure, a polyaramid based material is useful to form the one or more high modulus tensile members. 
     Now turning to  FIGS. 3A-3D  which show in side, or otherwise edge views, some examples of continuous toothed or grooved patterns useful as engaging structure for some sprockets according to the disclosure. In a first aspect shown in  FIG. 3A , a raised tooth pattern, such as that depicted at  108  in  FIGS. 1, and 206  in  FIG. 2 , surrounds the outer tooth periphery of body  304 , and is positioned between opposing and optional flanges  306  and  308 . The tooth pattern depicted may be useful for several applications, including, but not limited to, driving or being driven by a synchronous belt, or any belt with a mating face, as well as use as a synchronous sprocket, gear sprocket, coupling, and the like. 
       FIG. 3B  shows a belt engaging structure  312  continuously disposed on the periphery of body  314 , and which is shown positioned between opposing and optional flanges  316  and  318 . The belt engaging structure  312  is effective for driving or being driven by a poly-v belt. The belt engaging structure  312  is essentially a series of continuous parallel grooves embossed in the periphery of the body  314 . In some aspects, the surface of the belt engaging structure  312  may be embossed with a suitable textile reinforcement material. 
       FIG. 3C  depicts yet another belt engaging structure  322  which is useful for driving or being driven by so called offset tooth belts, some of which are commercially available under the name SILENTSYNC® from Continental Corporation, Fairlawn, Ohio. Offset belt engaging structure  322  is continuously disposed on the periphery of body  324 . Belt engaging structure  322  includes offset rows of teeth and landing portions designed to mesh with teeth on a mating offset tooth belt. Similar to that described above, the surface of the belt engaging structure  322  may be embossed with a suitable textile reinforcement material. 
       FIG. 3D  shows a belt engaging structure  332 , which engages a v-belt, continuously disposed on the periphery of body  334 , and which is shown positioned between opposing and optional flanges  336  and  338 . Here also, the surface of the belt engaging structure  332  may be embossed with a suitable textile reinforcement material. 
     Now referencing  FIG. 4 , which depicts high torque sprocket and bushing assembly  400  in a perspective view. Sprocket and bushing assembly  400  includes sprocket  402  and bushing  404 . While a QD bushing is shown as  404 , in some other aspects a tapered bushing may be used as well. Bushing  404  may be installed into recessed hub  406  defined by the body of sprocket  402  for receiving bushing  404 , and retained with any suitable fastening means, such as screws  408  (one shown) installed through ports  410  in bushing  404  which engage complimentary aligned threaded ports in the body of sprocket  402 , thus securing sprocket  402  and bushing  404  with one another. Alternatively, screws  408  could be installed from an opposing side of sprocket  402  through ports therein, and screwed into threaded ports  412  of bushing  404  to secure the sprocket  402  and bushing  404 . 
     Sprocket  402  may be of any suitable design according to the disclosure. In the embodiment shown in  FIG. 4 , sprocket  402  includes a body  414  defining an outer periphery and a recessed hub section  406  for engaging the bushing  404 . Continuous toothed structure  416  is disposed completely around the outer periphery of the body  414 . As described above, a textile reinforcement may embedded in the hub section  406  adjacent the inner surface, and/or a textile reinforcement may be embedded in the continuous toothed structure  416  outer surface. A flange  418  may be disposed on one or both sides of body  414  immediately adjacent the continuous toothed structure  416 , and a textile reinforcement may in some cases, be embedded in the side surface of the flange(s). 
     The bushing  404  may be formed of steel, or in some cases, formed from a castable polymer material, similar to that described herein for sprocket embodiments. In some embodiments, bushing  404  is formed of a castable polymer material essentially free or devoid of any metal structure(s) other than metallic threaded inserts and/or metallic collars installed within ports of the bushing. Alternatively, the bushing  404  may be formed of both castable polymer material and metal components. In some aspects, bushing  404  may have textile reinforcement material(s) embedded adjacent the outer surface of the portion of bushing  404  which is installed into hub section  406 . 
     Any suitable textile reinforcement materials may be used in embodiments according to the disclosure, including, but not limited to, woven or non-woven materials, in any desirable weight and orientation, and in some cases is comprised of multiple individual plies separated by appropriate elastomeric or adhesive layers. In some other aspects, the textile reinforcement are single plies. The textile reinforcement materials may be based upon a wide variety of synthetic and natural fibers, including polyester, nylon, aramid (e.g., Kevlar), glass, polypropylene, carbon cordage, cellulose, wool, or others. The fibers may be multi-filament, monofilament, or staple fibers. In some embodiments, the textile reinforcement materials are single plies of polyester and/or nylon. The polyester can be polyethylene terephthalate or polyethylene naphthalate. In some cases the polyester can be a copolyester that contains repeat units, which are derived from both terephthalic acid and isophthalic acid or dimethyl esters thereof. In such cases, the copolyester will typically contain at least about 95 weight percent terephthalic acid and up to about 5 weight percent isophthalic acid. More typically, the copolyester will contain at least about 97 weight percent terephthalic acid and up to about 3 weight percent isophthalic acid. The polyester fabric can optionally be made from polyester staple yarn to improve adhesion characteristics. The nylon fabrics that can be used in conjunction with this disclosure may be comprised of virtually any type of nylon, such as nylon-6,6, nylon-6,12, nylon-6,10, nylon-6,9, nylon-6, nylon-11, or nylon-12. For commercial reasons, the nylon will typically be nylon-6,6 or nylon-6. 
     Castable materials forming the sprocket bodies according to the disclosure include castable polymer materials, such as polyurethane polymers, polyester polymers, epoxy polymers, and the like. Polymer casting is a method of casting where a mold is filled with a liquid synthetic polymer, which then hardens. In embodiments according to the disclosure, casting may be accomplished with the liquid polymer plus an effective amount of a “hardener” liquid, which functionally contains a second polymer or reactant, for use in forming a final product which is a copolymer. Copolymers contain two different alternating chemical entities in the final polymer molecule. For example, in a polyurethane casting process, the polyurethane polymer structure may be formed by reacting a di- or polyisocyanate with a polyol. Both the isocyanates and polyols used to make polyurethanes contain on average two or more functional groups per molecule. The materials are mixed, introduced into the mold, and exposed to certain conditions (i.e. temperature, time, pressure, etc.) to form the polyurethane polymer structure or body. In some aspects, the sprocket bodies, or portions thereof, are prepared by a low pressure casting process where pressure within an empty mold is sufficiently reduced, and low pressure is used to transfer the reaction components into the empty mold, which then react and cast the sprocket body within the mold. In some other aspects, the sprockets are formed using a compression mold process which does not involve lowering pressure in the mold, but rather, high pressure is used to transfer the reaction components into the empty mold, and sufficient forces are placed on the components in the formation of the sprocket in the mold. 
     The polymeric materials used forming the sprocket bodies may also be mixed with various additives in conventional or suitable amounts known to persons having ordinary skill in the art. Such additives may include, and are not limited to, cross-linking agents, accelerators, retardants to prevent an unduly quick cure, antioxidants, aging resistance aids (e.g., ozone and UV resistance), adhesion promoters, processing aids, flame retardancy additives, reinforcing agents and fillers, such as carbon black, silica, other mineral fillers, lignin, fibers, friction modifiers such as UHMWPE and PTFE, and the like. In some cases, carbon black, silver salts, or any other suitable electrically conductive materials may also be added to control and/or reduce static electricity buildup. Reinforcing fillers are typically utilized at a level which is within the range of about 1 parts per hundred parts of resin (phr) to about 50 phr. 
     In some embodiments ultra-high molecular weight polyethylene (UHMWPE) is incorporated into the castable polymer material mixture in a suitable amount to provide increased durability to the sprocket. Any suitable shape of UHMWPE particles may be used, for example, powder, fibers, and the like. In cases where UHMWPE powder is used, the average size of the particles in the powder may be from about 20 microns to about 100 microns, from about 40 microns to about 80 microns, or even from about 50 microns to about 70 microns. The UHMWPE powder may be incorporated in suitable amounts, such as from about 1% to about 10% by weight of the castable polymer material, from about 2% to about 8% by weight of the castable polymer material, or even from about 3% to about 7% by weight of the castable polymer material. In any case, when the UHMWPE powder is incorporated into the castable polymer material mixture, the mixture needs to have a low enough viscosity to be processed through gear pumps on automated mixing equipment, which is typically used in the art for processing such products. 
     In some cases, the hardness of the final cured castable polymer material mixture including UHMWPE powder, or otherwise the produced sprocket, is from about 60 Shore D to about 100 Shore D hardness value, or even from about 75 Shore D to about 85 Shore D hardness value. 
     The advantages of embodiments according to the disclosure include a sprocket that is light weight and very wear resistant under high torque loads. The sprocket embodiments are also less costly to manufacture than existing art, and a flange or flanges can be added to the sprocket without significant additional cost. The sprocket embodiments also allow any desired cosmetic design to be easily cast into the sprocket, while creating a very accurate, strong, and wear resistant tooth and groove area. Also, the sprocket embodiments are corrosion resistant and do not require painting or other corrosion resistant finishes. 
     In application, embodiments of the disclosure may be useful for engaging such belts as a v-belt, poly v-belt, micro v-belt, or synchronous belt, and either driving or being driven by such belts. In other applications, the sprocket embodiments may also be used as a synchronous sprocket, gear sprocket, or coupling. 
     Embodiments according to the disclosure may be utilized over a range of suitable torque loads, both narrow and wide in scope; for example, from about 0.1 ft-lb to about 4,000 ft-lb, from about 10 ft-lb to about 1,000 ft-lb, about 150 ft-lb or greater, about 200 ft-lb or greater, about 250 ft-lb or greater, about 300 ft-lb or greater, or even about 400 ft-lb and above. Sprocket/pulley embodiments may be of any suitable diameter, such as, but not limited to from about 1 inch to about 45 inches in diameter. The width of the toothed structures may be of any suitable width, including about 0.25 inches wide to about 10 inches wide, or even from about 0.375 inches wide to about 8 inches wide. Also, the toothed structures may have any applicable tooth pitch, including, but not limited to 8 mm pitch to 14 mm pitch or any point there between. 
     In one testing example, a pair of sprockets, similar to that shown in  FIG. 1 , were each formed of castable polyurethane containing 5% by weight ultra-high molecular weight polyethylene (UHMWPE) powder having an average particle size of 60 microns. The sprockets further included a textile reinforcement embedded in the body adjacent the inner surface of the hub section. The pair of sprockets each had a tooth pitch of 14 mm, diameter of about 5.5 inches and 32 tooth continuous toothed structure having a width of 43 mm. They were mounted on shafts with a QD bushing installed in the hub. One sprocket was used as a driver and the other was driven. The driver sprocket was used to drive a 37 mm wide belt (ContiTech® belt number 14GTR-1750-37) at 2633 inch-lbs of torque at an RPM of 450 for 859 hrs, which in turn drove the driven sprocket. No failure or any other significant damage was noted in the sprockets after these test conditions, other than slight wear on the tooth surface. A comparative test was conducted on sprockets not including UHMWPE in the castable polyurethane, and such sprockets failed at 193 hours. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. Example embodiments are provided so that this disclosure will be sufficiently thorough, and will convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the disclosure, but are not intended to be exhaustive or to limit the disclosure. It will be appreciated that it is within the scope of the disclosure that individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 
     Also, in some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Further, it will be readily apparent to those of skill in the art that in the design, manufacture, and operation of apparatus to achieve that described in the disclosure, variations in apparatus design, construction, condition, erosion of components, gaps between components may present, for example. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner”, “adjacent”, “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated  90  degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.