Patent Publication Number: US-2021180733-A1

Title: Gimbals and their manufacture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This specification is based upon and claims the benefit of priority from United Kingdom patent application number GB 1918607.1 filed on Dec. 17, 2019, the entire contents of which is incorporated herein by reference. 
     BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to gimbals and a method of manufacturing gimbals. The gimbals may be used for example on gas turbine aircraft engines. 
     Description of the Related Art 
     A gimbal is a 3-dimensional connecting two ducts/pipes that allows for angular movements between the connected ducts/pipes by providing two orthogonal axes of rotation. Gimbals are often used, for example, to provide flexible connections in between certain parts of the ducting which are often long running and are installed between certain parts of a gas turbine aircraft engine. Having a flexible connection reduces the stresses that result from the duct&#39;s ends moving during engine manoeuvres and to reduce thermal stresses in the ducting during engine operation. 
       FIG. 1  shows known gimbals located on the fan case of a gas turbine aircraft engine. It is not uncommon for a gas turbine aircraft engine to have 10 to 15 gimbals. 
       FIG. 2  shows an exploded view of the known gimbal shown in  FIG. 1 . Each gimbal consists of 12 sub-components. The gimbals are manufactured using traditional extrusion, rolling and forming processes which require a number of welds to connect various pins, devises, bellows and flanges. Welding requires the services of skilled welders and yet components that fail in service often fail as a result of one or more welds used to manufacture the component failing. 
     The method of manufacturing the gimbal of  FIGS. 1 and 2  restricts the size, design and strength of the gimbal that is manufactured. The gimbal design does not have sufficient strength to contain pressurised liquids therefore currently, its use is limited to connecting ducts that carry air. 
     There is therefore a need to provide a gimbal that overcomes or at least minimises the disadvantages and limitations of the aforementioned known gimbal or at least provides a useful alternative to that and other known gimbals. 
     SUMMARY OF THE DISCLOSURE 
     According to a first aspect there is provided a gimbal for connecting pipes, the gimbal comprises a core portion and at least one joint shield portion that surrounds the core portion; the core portion, which has a core portion internal surface and a core portion external surface, comprises and at least two pipe engaging portions that are separated by at least one flexible portion, which has a flexible portion internal surface and a flexible portion external surface, and a plurality of joint cover portions; each joint cover portion extends from the core portion external surface of the core portion to provide a protective cover for the flexible portion external surface of at least one flexible portion of the core portion and is pivotably connected to a least one joint shield portion; the or each joint shield portion is configured to provide a protective shield for at least one flexible portion of the core portion; and the core portion and the or each joint shield portion are formed as a single unitary component. 
     The gimbal may be used for connecting pipes or ducts of the gas turbine engine. Benefits include reducing part count, avoiding the need for any welding, improving gimbal strength, providing a gimbal that is suitable for carrying fluids generally, and potentially providing a “fit-and-forget” component. 
     In some embodiments, the core portion and the or each joint shield portion are formed as a single unitary component by an additive layer manufacturing process. Additive layer manufacturing provides flexibility in the design, sizing and optimisation of gimbals for specific uses and applications. 
     In some embodiments, one or more of the core portion, the pipe engaging portions, the or each flexible portion, and the or each joint shield portion is cylindrical in cross-section. 
     Such portions being cylindrical, be that generally cylindrical or substantially cylindrical, provides structural strength, e.g. by balancing stresses, and is especially compatible with ducts and piping that are also cylindrical in cross-section. 
     In some embodiments, the gimbal has two or more joint cover portions that are equally spaced around the core portion of the gimbal. Such arrangements assist in providing structural strength to the gimbal. 
     In some embodiments, the core portion further comprises at least one core portion joint guard that provides protective cover for at least one flexible portion. Such arrangements optimise protective cover for the or each flexible portion. 
     In some embodiments, the core portion joint guard is configured to complement the configuration of the joint cover portion to maximise protective cover for at least one flexible portion of the gimbal. Such arrangements optimise protective cover for the flexible portion(s) and help to optimise the structural strength of the gimbal. 
     In some embodiments, the or each joint shield portion and the joint cover portions are configured to complement each other in order to maximise protective shielding for the or each flexible portion of the gimbal. Such arrangements optimise protective shielding for the flexible portion(s) and help to optimise the structural strength of the gimbal. 
     In some embodiments, the gimbal has two to six joint cover portions and a single joint shield portion. The provision of multiple joint cover portions optimises protective shielding for the flexible portion(s) of the gimbal and helps to optimise the structural strength of the gimbal. 
     In some embodiments, the gimbal has four joint cover portions, a single joint shield portion, and the core portion has two pipe engaging portions and a single flexible portion. Such an arrangement provides a first embodiment of the gimbal of the present disclosure that usefully balances structural strength and structural simplicity. 
     In some embodiments, at least one of the pipe engaging portions is elongated. Such an arrangement enables fluid flow to be directed through the gimbal. 
     In some embodiments, at least one of the pipe engaging portions is curved. Such an arrangement enables fluid flow to be directed through the gimbal, for example involving a change in the plane of the fluid flow whilst avoiding the critical stress location that would be formed by an elbow and that avoids involving any welding of separate parts. 
     In some embodiments, the gimbal has four joint cover portions, a single joint shield portion, and the core portion has three pipe engaging portions and one flexible portion. Such an arrangement usefully provides embodiments where one stream of fluid is separated in the gimbal into two streams of fluid, or two streams of fluid converge in the gimbal into a single stream of fluid. 
     In some embodiments, the gimbal has six to twelve joint cover portions, three joint shield portions, and the core portion has three pipe engaging portions and three flexible portions. Such an arrangement usefully provides embodiments where one stream of fluid is separated in the gimbal into two streams of fluid, or two streams of fluid converge in the gimbal into a single stream of fluid, with optimised flexibility and fluid directing capability. 
     In some embodiments, the gimbal has at least one compartment containing vibration stress dampening material. Such an arrangement can dampen vibration stresses. The compartment may, for example, be formed within the joint cover portion, for example, adjacent the first pipe engaging portion of the gimbal. 
     In some embodiments, each joint cover portion has an aperture that receives a pin portion that extends inwardly from the joint shield portion so the joint cover portion id pivotable with respect to the joint shield portion. 
     According to a second aspect there is provided a gas turbine engine that includes at least one gimbal of the first aspect. 
     According to a third aspect there is provided a method for manufacturing a gimbal of the first aspect, the method comprising forming a gimbal of the first aspect by additive layer manufacturing. 
     The skilled person will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. Furthermore except where mutually exclusive any feature described herein may be applied to any aspect and/or combined with any other feature described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments will now be described by way of example only, with reference to the Figures, in which: 
     
    
    
       FIG. 1  is a perspective view of a gas turbine engine with its nacelle removed and indicates where two known gimbals are located on the engine. 
       FIG. 2  is an exploded view of a known gimbal used on gas turbine engines. 
       FIG. 3  is a perspective view of a first embodiment of a gimbal of the present disclosure. 
       FIG. 4  is a vertical cross-sectional view of part of the first embodiment of the gimbal of the present disclosure shown in  FIG. 3 . 
       FIG. 5  is a perspective view of the first embodiment of a gimbal of the present disclosure fitted between portions of two cylindrical pipes. 
       FIG. 6  is a view through the interior of the first embodiment of a gimbal of the present disclosure fitted between portions of two cylindrical pipes. 
       FIG. 7  is a close-up view of the first embodiment of the gimbal of the present disclosure fitted between portions of two cylindrical pipes. 
       FIG. 8  is a perspective view of a second embodiment of a gimbal of the present disclosure. 
       FIG. 9  is a perspective view of a third embodiment of a gimbal of the present disclosure. 
       FIG. 10  is a perspective view of a fourth embodiment of a gimbal of the present disclosure. 
       FIG. 11  is a vertical cross-sectional view of part of a fifth embodiment of the gimbal of the present disclosure shown in  FIG. 3  that has vibration stress dampening material contained within a compartment formed within the gimbal. 
     The following table lists the reference numerals used in the drawings: 
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Ref no. 
                 Feature 
               
               
                   
                   
               
             
            
               
                   
                 10 
                 Gas turbine engine 
               
               
                   
                 20 
                 Known gimbal 
               
               
                   
                 21 
                 Liners 
               
               
                   
                 22 
                 Bellow 
               
               
                   
                 23 
                 Pin 
               
               
                   
                 24 
                 Body ring 
               
               
                   
                 25 
                 Weld Ring 
               
               
                   
                 26 
                 Clevises 
               
               
                   
                 28 
                 Pipe 
               
               
                   
                 30 
                 One-component gimbal 
               
               
                   
                 40 
                 Core portion 
               
               
                   
                 41 
                 Core portion internal surface 
               
               
                   
                 42 
                 Core portion external surface 
               
               
                   
                 43 
                 First pipe engaging portion 
               
               
                   
                 44 
                 Second pipe engaging portion 
               
               
                   
                 45 
                 Third pipe engaging portion 
               
               
                   
                 46 
                 Flexible portion 
               
               
                   
                 47 
                 Flexible portion internal surface 
               
               
                   
                 48 
                 Flexible portion external surface 
               
               
                   
                 49 
                 Core portion joint guard 
               
               
                   
                 50 
                 Joint cover portion 
               
               
                   
                 51 
                 Joint cover portion internal surface 
               
               
                   
                 52 
                 Joint cover portion external surface 
               
               
                   
                 60 
                 Joint shield portion 
               
               
                   
                 61 
                 Joint shield portion internal surface 
               
               
                   
                 62 
                 Joint shield portion external surface 
               
               
                   
                 64 
                 Pin portion 
               
               
                   
                 65 
                 Compartment 
               
               
                   
                 66 
                 Vibration stress dampening material 
               
               
                   
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     Aspects and embodiments of the present disclosure will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. 
     The present disclosure relates to a gimbal for use, for example in a gas turbine engine. The gimbal provides a flexible connection for pipes or ducting in a gas turbine engine. They are typically located on and around the core engine of a gas turbine engine connecting pipes and ducts that run into and out of the core engine. While the movement of such piping and ducting is typically restricted within the confines of a core engine nacelle, they are still prone to movement during engine operation. The use of flexible connections assists the arrangement of piping and ducting to resist the stresses placed on them during engine operation. 
     In broad terms the gimbal of the present disclosure comprises a core portion and at least one joint shield portion that that surrounds the core portion, the core portion and the at least one joint shield portion being formed as a single unitary component. 
       FIG. 3  shows a perspective view of a first embodiment of a gimbal  30  of the present disclosure. It may be used, for example, for connecting pipes, ducts and the like of a gas turbine engine. The gimbal  30  has a core portion  40  and a joint shield portion  60  that surrounds the core portion. The joint shield portion surrounds the core portion by encircling at least part of the core portion. The core portion and the joint shield portion form the gimbal as a single unitary component i.e. the gimbal is made and used as a single, one-part, component. 
     The core portion  40  of the gimbal  30  has a core portion internal surface  41  and a core portion external surface  42  and it comprises a first pipe engaging portion  43  and a second pipe engaging portion  44  that is separated by a flexible portion  46 . The flexible portion  46  has a flexible portion internal surface  47  and a flexible portion external surface  48 . The core portion further comprises a plurality of joint cover portions  50 . 
     The first pipe engaging portion  43  and the second pipe engaging portion  44  of the first embodiment of  FIG. 3  are cylindrical in cross-section to assist in providing fluid-tight connections to pipes and ducts that are also typically cylindrical in cross-section. The cylindrical cross-section also provides hoop strength and therefore assists in resisting internal pressures. 
     The gimbal of the first embodiment has four joint cover portions  50 , equally spaced around the periphery of the core portion  40 . Fully functional gimbals can be made with various numbers of joint cover portions, however for the first embodiment, four joint cover portions  50  were chosen to balance part strength for its intended purpose for use in connecting pipes in a gas turbine aircraft engine. 
     Each joint cover portion  50  of the first embodiment of gimbal  30  of the present disclosure has a joint cover portion internal surface  51  and a joint cover portion external surface  52 . The joint cover portion  50  extends from the core portion external surface  42  and is configured to protect at least part of the flexible portion external surface  48  of the flexible portion  40 . 
     Each joint cover portion  50  is pivotably connected to the joint shield portion  60 . This enables the gimbal to accommodate angular movements of the ducts that are connected by the gimbal. The manner in which the joint cover portions are pivotably connected to the joint shield portion in the first embodiment of gimbal of the present disclosure is described below. 
     The joint cover portion  50  may take various forms to fulfil its purpose. In the first embodiment shown in  FIG. 3  each of the four joint cover portions  50  has a common shape, two of those extending generally axially in one direction and the other two extending generally axially an opposed direction but they are all pivotably connected to the joint shield portion  60 . In this way the gimbal of the present disclosure is formed in a manner that is analogous in function to the devises  26  and body ring  24  of the gimbal shown in  FIGS. 1 and 2 . 
     In the embodiment shown in  FIG. 3  the core portion  40  of the gimbal  30  has at least one core portion joint guard  49  that extends from the core portion external surface  42 . In the Figure one can most easily see a core portion joint guard  49  that extends from the core portion external surface  42  that is adjacent the second pipe engaging portion  44  of the gimbal  30 . 
     The core portion joint guard  49  serves the purpose of providing a protective shield for part of the flexible portion  46 , for example the part of the flexible portion  46  that is not protected, or only partially protected, by the joint cover portion  50 . The core portion joint guard  49  may take various forms to fulfil its purpose. It may be annular to maximise protective cover for the flexible portion  46 . The length and/or shape of the core portion joint guard  49  may vary around the core portion  40 . The core portion joint guard  49  may be configured to complement the configuration of the joint cover portion  50 , for example in order to maximise protective shielding for the flexible portion  46  of the gimbal  30 . 
     In the first embodiment the core portion  40  has four core portion joint guards  49 , two each side of the joint shield portion  60 . Each core portion joint guard  49  forms part of the gimbal that extends from the core portion that forms adjoining the joint cover portions  50 . The arrangement is such that each core portion joint guard  49  faces a joint cover portion  50  the combination of the two providing a protective cover of the flexible portion  46  located between them. 
       FIG. 4  shows a vertical cross-sectional view of part of the first embodiment of the gimbal of the present disclosure shown in  FIG. 3 . This shows more clearly how the joint cover portions  50  are configured to provide protective cover for the flexible portion  46  of the core portion  40  and how the joint cover portions  50  are pivotably connected to the joint shield portion  60 .  FIG. 4  also shows more clearly how each of the joint cover portions  50  can work in concert with each of the four core portion joint guards  49  to protect the flexible portion  46 . 
     The joint shield portion  60  has a joint shield portion internal surface  61  and a joint shield portion external surface  62 . The joint shield portion  60  may take various forms to fulfil its purpose. It may be annular to maximise protective cover for the flexible portion  46  and the joint cover portion  50 , e.g. as per the first embodiment. In other embodiments the width and/or shape of the joint shield portion  60  may vary around the core portion  40 . The joint shield portion  60 , the joint cover portion  50 , and the core portion joint guards  49  are configured to complement each other, for example in order to maximise protective shielding for the flexible portion  46  of the gimbal  30 . 
     In the embodiment of the gimbal of the present disclosure shown in  FIG. 4 , the joint shield portion  60  has a pin portion  64  that extends inwardly from the joint shield portion, i.e. towards the flexible portion  46  and passes through an aperture formed in the joint cover portion  50 . The pin portion  64  is integral to the joint shield portion  60  and enables the joint cover portion  50  to be pivotable with respect to the joint shield portion  60 . 
     The core portion  40  and the joint shield portion  60  are formed as a single unitary component i.e. they form a one-piece gimbal. This provides several benefits:
         It reduces the part count i.e. the number of component of the gimbal. For example from 12 for the known gimbal shown in  FIGS. 1 and 2  to one of the gimbal of the present disclosure. Reducing complexity and thus reduces part failures, maintenance times, maintenance costs and part storage.   It avoids the need for any welding, which is a time consuming and highly skilled activity.   It provides the potential for improved gimbal strength by avoiding the use and interaction of multiple parts and removing welds.   It provides the potential to suit different clamping or connection options.   It provides the potential to improve system dampening, for example by incorporating pockets or compartments in the gimbal that can be filled with materials that dampen vibration stresses.   It provides the potential for the gimbal to suitable for connecting fuel- and oil-carrying pipes and ducts rather than be limited to connecting air-carrying and other gas-carrying pipes and ducts.   It provides the potential for a gimbal of the present disclosure to be a “fit-and-forget” component i.e. once fitted in a machine, for example a gas turbine engine, it can be relied upon to require minimal and potentially no maintenance for working life of the machine.       

     Gimbals of the present disclosure are useful to flexibly connect piping or ducting to certain parts of a gas turbine aircraft engine.  FIGS. 5, 6 and 7  depict the above described first embodiment of a gimbal of the present invention flexibly connecting two pipes  28  of a gas turbine engine. 
       FIG. 5  is a perspective view of the first embodiment of a gimbal  30  of the present disclosure fitted between portions of two cylindrical pipes  28 . One end of one of the pipes  28  is secured to the first pipe engaging portion  43  of the gimbal  30  and one end of the other pipe  28  is secured to the second pipe engaging portion  44  of the gimbal  30 . The pipes  28  can be secured to first and second pipe engaging portions  43  and  44  by any suitable means. In some arrangements the pipes are permanently fixed to one or both of the first and second pipe engaging portions of the gimbal. In other arrangements the pipes are removably secured to one or both of the first and second pipe engaging portions of the gimbal. 
       FIG. 6  is a view through the interior of the first embodiment of a gimbal  30  of the present disclosure fitted between portions of two cylindrical pipes  28  of a gas turbine engine. Part of the flexible portion internal surface  47  of the flexible portion  46  of the gimbal  30  is visible through the portion of the pipe  28  in the foreground. One can also see a pin portion  64  of the joint shield portion  60  of the gimbal  30  is received by an aperture in a joint cover portion  50  of the gimbal. 
       FIG. 7  is a close-up view of the first embodiment of the gimbal of the present disclosure fitted between portions of two cylindrical pipes. Part of the flexible portion external surface  48  of the flexible portion  46  of the gimbal  30  is visible between the joint shield portion  60  of the gimbal  30  and a joint cover portion  50  of the gimbal  30 . 
     Various technologies are known for manufacturing parts as single unitary component. In some embodiments the gimbal of the present disclosure is manufactured by Additive Layer Manufacturing (ALM), also known as “3D printing”. Additive Layer Manufacturing involves building a three-dimensional object from a computer-aided design (CAD) model, usually by successively adding material layer by layer. This is in contrast to conventional machining, casting and forging processes, where material is removed from a stock item (subtractive manufacturing) or poured into a mold and shaped by means of dies, presses and hammers. 
     The flexibility of Additive Layer Manufacturing enables the gimbal of the present disclosure to be designed and made with optimised thermal, vibration and impact load stress relief for a wide variety of pipe/duct designs, thicknesses, diameters, and connection types. Gimbals of the present disclosure e.g. ALM gimbals of the present disclosure, can be designed to suit different clamping/connecting options. Gimbal corrugations can be optimised to meet strength and stiffness requirements. Gimbal corrugations and joints can be optimised to improve system damping. The pipe engaging portions can be formed for bespoke applications e.g. involving different configurations. A single gimbal of the present disclosure can be printed in multiple materials suited to specifics uses and/or use locations. This is can be especially important when manufacturing gimbals for use in gas turbine engine where pipe/duct can exposed to extreme temperatures and pressures during operation. 
     Additive Layer Manufacturing enables a wide variety of material options from which to form gimbals of the present disclosure. ALM gimbals can be used in critical stress locations of pipes/ducts of gas turbine engines, e.g. elbows, to reduce stress levels caused by end interface movements, vibrations and thermal loading as well as extreme impact loading such as Fan Blade Off (FBO) or Core Blade Off (CBO). 
     As evident from the above, gimbals of the present disclosure can take a variety of forms and can be manufactured to meet a variety of needs.  FIGS. 3 to 7  depict one embodiment of a gimbal of the present disclosure that is suitable for connecting fluid pipes and ducts in a gas turbine engine.  FIGS. 8, 9 and 10  depict three additional embodiments to assist in illustrating the flexibility of the gimbal of the present disclosure at least with respect to the configuration of the gimbal. 
       FIG. 8  shows a perspective view of a second embodiment of a gimbal of the present disclosure. This gimbal has a core portion  40 , four joint cover portions  50  and a joint shield portion  60  that form a single unitary component. The core portion  40  has a first pipe engaging portion  43  and a second pipe engaging portion  44  separated by a flexible portion  46 . However while the first pipe engaging portion  43  resembles that of the first embodiment of  FIGS. 3 to 7 , the second pipe engaging portion  44  is elongated i.e. longer that of the first embodiment, and it is curved. The curved nature of the second pipe engaging portion  44  serves to guide fluid carried within it to a desired axis which is different to the axis of the first pipe engaging portion  43  whilst avoiding the need to weld a separate elbow and thereby improving the strength in these areas. 
       FIG. 9  shows a perspective view of a third embodiment of a gimbal of the present disclosure. This gimbal has a core portion  40 , four joint cover portions  50  and a joint shield portion  60  that form a single unitary component. The core portion  40  has a first pipe engaging portion  43  that resembles that of the first embodiment of  FIGS. 3 to 7 . However the core portion  40  has a second pipe engaging portion  44  and a third pipe engaging portion  45  so that the gimbal can connect three pipes or ducts. A flexible portion  46  separates the first pipe engaging portion  43  from the second pipe engaging portion  44  and the third pipe engaging portion  45 . Such an arrangement is useful, for example, when one stream of fluid into the gimbal is separated into two streams of fluid, or when two streams of fluid converge in the gimbal into a single stream of fluid. The second pipe engaging portion  44  and the third pipe engaging portion  45  are elongated with respect to the first pipe engaging portion  43  and they are angled to provide different inlet and outlet axes. The axes&#39; angular orientation can be chosen as per the requirement to support the pipes/ducts routing. 
       FIG. 10  shows a perspective view of a fourth embodiment of a gimbal of the present disclosure. This gimbal has a core portion  40 , twelve joint cover portions  50  and three joint shield portions  60  that form a single unitary component. The core portion  40  has a first pipe engaging portion  43  that resembles that of the first embodiment of  FIGS. 3 to 7  as well as a second pipe engaging portion  44  and a third pipe engaging portion  45  so that the gimbal can connect three pipes or ducts. The first pipe engaging portion  43  and the second pipe engaging portion  44  are separated by two flexible portions  46 , the first pipe engaging portion  43  and the third pipe engaging portion  44  are separated by two flexible portions  46 , and the second pipe engaging portion  44  and the third pipe engaging portion  44  are separated by two flexible portions  46 . The second pipe engaging portion  44  and the third pipe engaging portion  45  are elongated with respect to the first pipe engaging portion  43  and they are angled. Such an arrangement is useful, for example, when one stream of fluid is separated in the gimbal into two streams of fluid, or when two streams of fluid converge in the gimbal into a single stream of fluid. 
       FIG. 11  shows a vertical cross-sectional view of part of the fifth embodiment of a gimbal of the present disclosure. This embodiment resembles the first embodiment however it includes the aforementioned pockets or compartments  65  in the gimbal that are filled with a material  66 , for example a powdered material, which dampens vibration stresses. The pockets or compartments  65  are formed in the joint cover portion adjacent the first pipe engaging portion of the gimbal. 
     As mentioned above, various technologies are known for manufacturing parts as single unitary components. These technologies include Additive Layer Manufacturing (ALM), which offers great flexibility in the manufacture of one component gimbals. Additive Layer Manufacturing (ALM) covers a variety of methods that involve building a three-dimensional object from a computer-aided design (CAD) model, usually by adding material layer by layer. 
     One skilled in the art can choose a material that is suitable to meet the service requirements for the gimbal. For example, the material may comprise one or more of titanium, a titanium alloy, steel, a steel alloy, aluminium, an aluminium alloy and a nickel-based superalloy. 
     While the gimbal of the present disclosure has been described with reference to embodiments that are suitable for use in gas turbine engines, for example gas turbine aircraft engines, it should be understood that the gimbal of the present disclosure could be used for other purposes and in other industries. For example in domestic or commercial plumbing, air conditioning or heating. It may also have application in automotive, marine, submarine, industrial power, nuclear, oil and gas industries. 
     It will be understood that the invention is not limited to the embodiments above-described and various modifications and improvements can be made without departing from the concepts described herein. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.