EXHAUST GAS SYSTEM

Description

INTRODUCTION

The information provided in this section is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

The present disclosure relates generally to a vehicle and, more particularly, to an exhaust gas system for a vehicle.

Motor vehicles comprising internal combustion engines typically have catalytic converters, which provide exhaust gas aftertreatment by removing pollutant from the exhaust gas. While catalytic converters remove pollutant from exhaust gas, existing aftertreatment systems commonly struggle to eliminate pollutant emissions before they reach the atmosphere during a catalytic light-off (CLO) period (i.e., 10-20 seconds after ignition of an internal combustion engine). Shortcomings of these systems are addressed by one or more aspects of the present disclosure.

SUMMARY

In one configuration, a vehicle is provided and includes a vehicle body, an internal combustion engine coupled to the vehicle body and including an exhaust gas manifold, and an exhaust gas system coupled to the vehicle body. The exhaust gas system including a primary catalyst including a main body having a first end, a second end spaced from the first end, and at least one wall extending between the first end and the second end, an inlet coupled to the first end, and an outlet coupled to the second end. The main body is arranged downstream of the internal combustion engine and the inlet is communicatively coupled to the exhaust gas manifold. The exhaust gas system further including a heat source arranged about a portion of the main body and configured to supply heat to the primary catalyst during a catalytic light-off (CLO) period.

The vehicle may include one or more of the following optional aspects. For example, the at least one wall defines a circumference that extends between the first end and the second end. The heat source includes a first heat source arranged about a first portion of the main body that is adjacent the first end. The heat source includes a second heat source arranged about a second portion of the main body that is adjacent to the first heat source and the second end. The exhaust gas system can further include a secondary catalyst arranged downstream of the internal combustion engine. The exhaust gas system can further include a valve communicatively coupled to the exhaust gas manifold, the primary catalyst, and the secondary catalyst. The valve can be configured direct flow towards the primary catalyst or the secondary catalyst depending on a temperature of the primary catalyst. The primary catalyst can be configured to operate at a first temperature range and the secondary catalyst can be configured to operate at a second temperature range that is different from the first temperature range.

According to at least one aspect, the exhaust gas system can further include a secondary catalyst arranged downstream of the primary catalyst and communicatively coupled to the outlet of the primary catalyst. The exhaust gas system can further include a valve arranged between the primary catalyst and the secondary catalyst and is configured to bypass the secondary catalyst after the CLO period.

In another configuration, an exhaust gas system is provided and includes an inlet arranged at a first end, an outlet arranged at a second end, a primary catalyst including a first face, a secondary catalyst including a second face and arranged radially about the primary catalyst, a thermal interface between the primary catalyst and the secondary catalyst, and a valve arranged axially between the inlet and the first and second faces, the valve being configured to selectively direct exhaust gas toward one or both of the first face and the second face.

The exhaust gas system may include one or more of the following optional aspects. For example, the valve includes a first position that prevents exhaust gas from reaching the first face of the primary catalyst. The thermal interface can be configured to transfer heat from the secondary catalyst to the primary catalyst when the valve is in the first position. The valve can include a second position that directs exhaust gas toward the first face and the second face. The primary catalyst can be configured to operate at a first temperature range and the secondary catalyst can be configured to operate at a second temperature range that is included in the first temperature range.

In another configuration, an exhaust gas aftertreatment device is provided and includes a primary catalyst including a first face and made of a platinum group material, a secondary catalyst including a second face and arranged radially about the primary catalyst, and a thermal interface between the primary catalyst and the secondary catalyst that is configured to transfer heat between the primary catalyst and the secondary catalyst during a catalytic light-off period.

The exhaust gas system may include one or more of the following optional aspects. For example, the platinum group material consists of at least one of: ruthenium, rhodium, palladium, osmium, iridium, and platinum.

According to at least one aspect, the secondary catalyst consists of at least one of: hopcalite, perovskite, and platinized tin oxide. The first face and the second face can be coplanar. The secondary catalyst can be configured to achieve a catalytic light-off (CLO) temperature prior to the primary catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustrative purposes only of selected configurations and are not intended to limit the scope of the present disclosure.

FIG. 1 is a front perspective view of a vehicle according to principles of the present disclosure;

FIG. 2 is a schematic view of an engine and a first configuration of an exhaust gas system having a primary catalyst;

FIG. 3 is a close-up view of the primary catalyst of FIG. 2 having a heat source arranged at a first end;

FIG. 4 is a close-up view of the primary catalyst of FIG. 2 having a first heat source arranged at a first end and a second heat source arranged at a second end;

FIG. 5 is a schematic view of an engine and another configuration of an exhaust gas system having a primary catalyst and a secondary catalyst;

FIG.6 is a schematic view of an engine and another configuration of an exhaust gas system having a primary catalyst and a secondary catalyst;

FIG. 7A is a schematic view of an engine and an exhaust gas aftertreatment device according to the principles of the present disclosure;

FIG. 7B is a cross-sectional view of the exhaust gas aftertreatment device of FIG. 7A; and

FIG. 8 is a schematic view of an engine and another configuration of an exhaust gas system having a primary catalyst and a secondary catalyst.

Corresponding reference numerals indicate corresponding parts throughout the drawings.

DETAILED DESCRIPTION

Example configurations will now be described more fully with reference to the accompanying drawings. Example configurations are provided so that this disclosure will be thorough, and will fully convey the scope of the disclosure to those of ordinary skill in the art. Specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of configurations of the present disclosure. It will be apparent to those of ordinary skill in the art that specific details need not be employed, that example configurations may be embodied in many different forms, and that the specific details and the example configurations should not be construed to limit the scope of the disclosure.

The terminology used herein is for the purpose of describing particular exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. Additional or alternative steps may be employed.

When an element or layer is referred to as being “on,” “engaged to,” “connected to,” “attached to,” or “coupled to” another element or layer, it may be directly on, engaged, connected, attached, or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” “directly attached to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

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 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 configurations.

In this application, including the definitions below, the term “module” may be replaced with the term “circuit.” The term “module” may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip.

The term “code,” as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term “shared processor” encompasses a single processor that executes some or all code from multiple modules. The term “group processor” encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term “shared memory” encompasses a single memory that stores some or all code from multiple modules. The term “group memory” encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term “memory” may be a subset of the term “computer-readable medium.” The term “computer-readable medium” does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory memory. Non-limiting examples of a non-transitory memory include a tangible computer readable medium including a nonvolatile memory, magnetic storage, and optical storage.

The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory tangible computer readable medium. The computer programs may also include and/or rely on stored data.

A software application (i.e., a software resource) may refer to computer software that causes a computing device to perform a task. In some examples, a software application may be referred to as an “application,” an “app,” or a “program.” Example applications include, but are not limited to, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications.

The non-transitory memory may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by a computing device. The non-transitory memory may be volatile and/or non-volatile addressable semiconductor memory. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM)/programmable read-only memory (PROM)/erasable programmable read-only memory (EPROM)/electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM) as well as disks or tapes.

These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, non-transitory computer readable medium, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor.

Various implementations of the systems and techniques described herein can be realized in digital electronic and/or optical circuitry, integrated circuitry, specially designed ASICS (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device.

The processes and logic flows described in this specification can be performed by one or more programmable processors, also referred to as data processing hardware, executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user's client device in response to requests received from the web browser.

With reference to FIG. 1, a vehicle 10 is provided and includes a vehicle body 12. The vehicle 10 further includes an internal combustion engine 14 coupled to the vehicle body 12. The internal combustion engine 14 can include an engine block 16, a cylinder head, one or more cylinders, and an exhaust gas manifold 18 that is coupled to the engine block 16 and configured to capture and direct exhaust gas away from the internal combustion engine 14 during operation. The vehicle 10 can further include an exhaust gas system 100 communicatively coupled to the internal combustion engine 14 and, more particularly, to the exhaust gas manifold 18. In general, the exhaust gas system 100 is configured to treat exhaust gas before it exits the vehicle 10 and enters the atmosphere surrounding the vehicle 10.

With reference to FIG. 2, the exhaust gas system 100 includes a first or primary catalyst 102 that has a main body 104. The main body 104 has a first end 106, a second end 108 spaced from the first end 106, and at least one wall 110 extending between the first end 106 and the second end 108. The at least one wall 110 can define a circumference 112 or a perimeter that extends between the first end 106 and the second end 108. The primary catalyst 102 further includes an inlet 114 coupled to the main body 104 at the first end 106 and an outlet 116 coupled to main body 104 at the second end 108. In the present illustrative example, the main body 104 is arranged downstream of the internal combustion engine 14 and the inlet 114 is communicatively coupled to the exhaust gas manifold 18. According to one aspect, the primary catalyst 102 can be made of a platinum group material that includes at least one of: ruthenium, rhodium, palladium, osmium, iridium, and platinum.

With reference to FIG. 3, according to one aspect, the exhaust gas system 100 can further include a heat source 118 arranged about a portion of the main body 104 and configured to supply heat to the primary catalyst 102 during a catalytic light-off (CLO) period. The CLO period can refer to an amount time until one or more catalysts have reached a minimum temperature necessary for a catalytic reaction. The heat source 118 is configured to shorten the CLO period which is desirable to reduce harmful emissions from entering the atmosphere, for example. The heat source 118 can include a resistive heat source or an inductive heat source, for example. As shown in FIG. 3, a first heat source 120 is arranged about a first portion of the main body 104 that is adjacent the first end 106. A second heat source 122 can be arranged about a second portion of the main body 104 and adjacent to the first heat source 120 and the second end 108, as shown in FIG. 4.

FIG. 5 illustrates another illustrative configuration of an exhaust gas system 200. This configuration is similar in many respects to the configuration of FIGS. 2-4. Accordingly, the descriptions of the configurations are hereby incorporated into one another, and description of subject matter common to the configurations generally may not be repeated.

With reference to FIG. 5, the exhaust gas system 200 is shown communicatively coupled to the internal combustion engine 14. The exhaust gas system 200 includes a first or primary catalyst 202 and a second or secondary catalyst 204 that are both arranged downstream of the internal combustion engine 14. More specifically, the secondary catalyst 204 is arranged downstream of the internal combustion engine 14 but upstream of the primary catalyst 202. The primary catalyst 202 can be configured to operate at a first temperature range and the secondary catalyst 204 can be configured to operate at a second temperature range that is different from the first temperature range. Stated differently, the secondary catalyst 204 can be made of a material that achieves a CLO temperature prior to the primary catalyst 202. According to one aspect, the first temperature range is a higher temperature range than the second temperature range.

With continued reference to FIG. 5, the exhaust gas system 200 can include a valve 206 that is communicatively coupled to the exhaust gas manifold 18, the primary catalyst 202, and the secondary catalyst 204. A bypass channel 208 can be communicatively coupled to the valve 206 and the primary catalyst 202 so that exhaust gas can bypass the secondary catalyst 204 and flow from the internal combustion engine 14 to the primary catalyst 202. According to one aspect, the valve 206 can be a passive valve which is controlled via a bimetal spring or shape spring or an active valve that is controlled by a servo motor and an Electronic Control Unit (ECU), for example. According to another aspect, the valve 206 can have a first position (FIG. 5) and a second position (not shown). In the first position, the valve 206 directs flow of exhaust gas from the internal combustion engine 14 so that the exhaust gas can be treated by the secondary catalyst 204 before being treated by the primary catalyst 202. This may be desirable during a CLO period of the primary catalyst 202, especially if the secondary catalyst 204 is configured to achieve CLO before the primary catalyst 202, for example. In the second position, the valve closes off flow of exhaust gas to the secondary catalyst 204 and directs exhaust gas directly to the primary catalyst 202. This may be desirable once the primary catalyst 202 reaches its CLO temperature, as the primary catalyst 202 can be configured to operate at a higher temperature range, for example. As described, the valve 206 can be configured to direct flow towards the primary catalyst 202 or the secondary catalyst 204 depending on a temperature of the primary catalyst 202.

FIG. 6 illustrates another illustrative configuration of an exhaust gas system 300. This configuration is similar in many respects to the configuration of FIGS. 2-4 and FIG. 5. Accordingly, the descriptions of the configurations are hereby incorporated into one another, and description of subject matter common to the configurations generally may not be repeated.

With reference to FIG. 6, the exhaust gas system 300 is shown communicatively coupled to the internal combustion engine 14. The exhaust gas system 300 includes a first or primary catalyst 302 and a second or secondary catalyst 304 that are both arranged downstream of the internal combustion engine 14. More specifically, the secondary catalyst 304 is arranged downstream of both of the internal combustion engine 14 and the primary catalyst 302. The primary catalyst 302 can be configured to operate at a first temperature range and the secondary catalyst 304 can be configured to operate at a second temperature range that is different from the first temperature range. Stated differently, the secondary catalyst 304 can be made of a material that achieves a CLO temperature prior to the primary catalyst 302. According to one aspect, the first temperature range is a higher temperature range than the second temperature range.

With continued reference to FIG. 6, the exhaust gas system 300 can include a valve 306 that is arranged downstream of the primary catalyst 302 and communicatively coupled to the primary catalyst 302, the secondary catalyst 304, and a bypass channel 308. The bypass channel 308 can be configured to bypass the secondary catalyst 304 and carry exhaust gas to the atmosphere surrounding the vehicle 10. According to one aspect, the valve 306 can be a passive valve which is controlled via a bimetal spring or shape spring or an active valve that is controlled by a servo motor and an ECU, for example. According to another aspect, the valve 306 can have a first position (FIG. 6) and a second position (not shown). In the first position, the valve 306 directs flow of exhaust gas from the primary catalyst so that the exhaust gas can be subsequently treated by the secondary catalyst 304. This may be desirable during a CLO period of the primary catalyst 302, especially during a period when the primary catalyst 302 has not achieved its CLO temperature, for example. In the second position, the valve 306 closes off flow of exhaust gas to the secondary catalyst 304 and directs exhaust gas directly to the bypass channel 308. Bypassing the secondary catalyst 304 after a CLO period of the primary catalyst 302 (i.e., once the primary catalyst 302 achieves its CLO temperature) may be desirable to protect the secondary catalyst 304 from exhaust gas that exceeds an operating temperature range of the secondary catalyst 304. Thus, according to one aspect, the valve 306 can be configured to direct flow away from the secondary catalyst 304 depending on a temperature of primary catalyst 302.

FIGS. 7A and 7B illustrate another illustrative configuration of an exhaust gas system 400. This configuration is similar in many respects to the configurations of FIGS. 2-4, FIG. 5, and FIG. 6. Accordingly, the descriptions of the configurations are hereby incorporated into one another, and description of subject matter common to the configurations generally may not be repeated.

With reference to FIG. 7A, an exhaust gas system 400 is provided and shown communicatively coupled to the internal combustion engine 14. The exhaust gas system 400 includes an exhaust gas aftertreatment device 401 that includes a first end 402 and a second end 404 spaced from the first end 402. An inlet 406 is arranged at the first end 402 and an outlet 408 is arranged at the second end 404. The exhaust gas aftertreatment device 401 includes a first or primary catalyst 410 and a second or secondary catalyst 412 that are arranged between the inlet 406 and the outlet 408. According to one aspect, the primary catalyst 410 can be made of a platinum group material which consists of at least one of: ruthenium, rhodium, palladium, osmium, iridium, and platinum. Additionally or alternatively, the secondary catalyst 412 can be made of at least one of the following materials: hopcalite, perovskite, and platinized tin oxide. According to one aspect, the secondary catalyst 412 can be configured to achieve a CLO temperature prior to the primary catalyst 410. The primary catalyst 410 can be configured to operate at a first temperature range and the secondary catalyst 412 can configured to operate at a second temperature range that is included in the first temperature range.

In the present illustrative example, with reference to FIG. 7B, the secondary catalyst 412 is arranged radially about the primary catalyst 410. In other words, the primary catalyst 410 and the secondary catalyst 412 can be concentrically arranged with respect to the inlet 406 and/or the outlet 408. A thermal interface 414 is arranged radially between the primary catalyst 410 and the secondary catalyst 412 and can be configured to transfer heat from the secondary catalyst 412 to the primary catalyst 410 to heat up the primary catalyst 410 during a CLO period of the primary catalyst 410, for example. The primary catalyst 410 includes a first face 416 that faces toward the inlet 406 and the secondary catalyst 412 includes a second face 418 that also faces toward the inlet 406, as shown in FIG. 7B. According to one aspect, the first face 416 and the second face 418 can be coplanar with respect to one another as shown in FIG. 7A.

The exhaust gas aftertreatment device 401 can further include a flow funnel or channel 420 that is arranged axially between the inlet 406 and the first and second faces 416, 418. The flow funnel 420 includes a first opening 422 and a second opening 424 spaced from the first opening, and can be generally concentric with at least the primary catalyst 410 so that a majority of the exhaust gas that passes the inlet 406 can be directed at the first face 416.

With continued reference to FIG. 7A, the exhaust gas aftertreatment device 401 can further include a valve 426 arranged axially between the inlet 406 and the first and second faces 416, 418. In the present illustrative example, the valve 426 can be arranged with respect to the first opening 422 of the flow funnel 420 and can be configured to selectively direct exhaust gas toward one or both of the first face 416 and the second face 418. For instance, the valve 426 includes a first position (FIG. 7A) that prevents exhaust gas from the first face 416 of the primary catalyst 410. In the first position of the valve 426, exhaust gas is directed toward the secondary catalyst 412 and heat from the exhaust gas passes through the thermal interface 414 to the primary catalyst 410 to help heat up the primary catalyst 410 during a CLO period, for example. The valve 426 also includes a second position where exhaust gas can flow toward the first face 416 and the second face 418.

FIGS. 8 illustrates another illustrative configuration of an exhaust gas system 500. This configuration is similar in many respects to the configuration of FIGS. 2-4, FIG. 5, FIG. 6, and FIGS. 7A-7B. Accordingly, the descriptions of the configurations are hereby incorporated into one another, and description of subject matter common to the configurations generally may not be repeated.

With reference to FIG. 8, an exhaust gas system 500 is provided and shown communicatively coupled to the internal combustion engine 14. The exhaust gas system 500 includes a primary catalyst 502 and a secondary catalyst 504. In the present illustrative example, the secondary catalyst 504 is shown communicatively coupled to the exhaust gas manifold 18 and arranged upstream of the primary catalyst 502. Additionally, the secondary catalyst 504 is arranged adjacent the primary catalyst 502 such that there is a thermal interface 506 between the secondary catalyst 504 and the primary catalyst 502. Heat from the exhaust gas that travels through the secondary catalyst 504 can be transferred axially through the thermal interface 506 to help heat a face of the primary catalyst 502 during a CLO period, for example.

A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.

The foregoing description has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular configuration are generally not limited to that particular configuration, but, where applicable, are interchangeable and can be used in a selected configuration, 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.