Pluggable module for a communication system

A pluggable module includes a pluggable body extending lengthwise between a mating end and a cable end. The pluggable body has a first end and an opposite second end with sides extending therebetween along a length of the pluggable body. The first end, second end and sides define a cavity. An internal circuit board is held in the cavity. The internal circuit board is provided at an end of a cable communicatively coupled to the internal circuit board. The pluggable body is configured to be plugged into a receptacle assembly such that the internal circuit board is communicatively coupled to a communication connector of the receptacle assembly. The pluggable body is defined by a first shell including the first end and the sides and may be formed by extrusion and may have increased thermal conductivity and a second shell including the second end.

BACKGROUND OF THE INVENTION

The subject matter described herein relates to a pluggable module for a communication system.

At least some known communication systems include receptacle assemblies, such as input/output (I/O) connector assemblies, that are configured to receive a pluggable module and establish a communicative connection between the pluggable module and an electrical connector of the receptacle assembly. As one example, a known receptacle assembly includes a receptacle housing that is mounted to a circuit board and configured to receive a small form-factor (SFP) pluggable transceiver. The receptacle assembly includes an elongated cavity that extends between an opening of the cavity and an electrical connector that is disposed within the cavity and mounted to the circuit board. The pluggable module is inserted through the opening and advanced toward the electrical connector in the cavity. The pluggable module and the electrical connector have respective electrical contacts that engage one another to establish a communicative connection.

One challenge often encountered in the design of the pluggable module and receptacle assembly is the heat generated during operation of the communication system, which negatively affects module/system reliability and electrical performance. Typically, heat is generated by components on the internal circuit board within the pluggable module and drawn away from the internal circuit board by the metal body of the pluggable module. In some cases, a heat sink that is held by the receptacle assembly housing in direct contact with the metal body of the pluggable module is used to transfer the heat from the pluggable module. Air flowing through and around the receptacle assembly transfers the heat that emanates from the pluggable module. As data throughput speeds of the pluggable modules increase, more heat is generated. Conventional designs are proving to be inadequate for the required heat transfer.

Accordingly, there is a need for a pluggable module for use in a communication system that allows significant heat transfer.

BRIEF DESCRIPTION OF THE INVENTION

In an embodiment, a pluggable module is provided including a pluggable body extending lengthwise between a mating end and a cable end. The pluggable body has a first end and an opposite second end with sides extending therebetween along a length of the pluggable body. The first end, second end and sides define a cavity. An internal circuit board is held in the cavity. The internal circuit board is provided at an end of a cable communicatively coupled to the internal circuit board. The pluggable body is configured to be plugged into a receptacle assembly such that the internal circuit board is communicatively coupled to a communication connector of the receptacle assembly. The pluggable body is defined by a first shell and a second shell. The first shell includes the first end and the sides. The second shell includes the second end.

In another embodiment, a pluggable module is provided including a pluggable body defined by an extruded shell and a die cast shell coupled to the extruded shell. The extruded shell includes a first end extending lengthwise between a mating end and a cable end. The die cast shell includes a second end extending lengthwise between the mating end and the cable end. At least one of the extruded shell and the die cast shell includes sides between the first and second ends. The first end, second end and sides define a cavity. An internal circuit board is held in the cavity. The internal circuit board is provided at an end of a cable communicatively coupled to the internal circuit board. The pluggable body is configured to be plugged into a receptacle assembly such that the internal circuit board is communicatively coupled to a communication connector of the receptacle assembly.

In a further embodiment, a pluggable module is provided including a pluggable body defined by a first shell and a second shell. The first shell includes a first end extending lengthwise between a mating end and a cable end. The second shell includes a second end extending lengthwise between the mating end and the cable end. At least one of the first shell and the second shell include sides between the first and second ends. The first end, second end and sides define a cavity. An internal circuit board is held in the cavity. The internal circuit board is provided at an end of a cable communicatively coupled to the internal circuit board. The pluggable body is configured to be plugged into a receptacle assembly such that the internal circuit board is communicatively coupled to a communication connector of the receptacle assembly. The first shell has a uniform cross-section along the length between the mating end and the cable end. The second shell has a non-uniform cross-section between the mating end and the cable end. The non-uniform cross-section is defined by at least one pocket receiving the electrical component of the internal circuit board.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments set forth herein include communication systems and pluggable modules of the same. The pluggable module provides significant thermal heat dissipation or transfer for the components thereof. Various embodiments of the pluggable module include a pluggable body having a cost effective design. Various embodiments of the pluggable module include a pluggable body that facilitates significant heat transfer.

Unlike conventional pluggable modules that utilize an upper shell and a lower shell both having complex features, embodiments set forth herein have one of the shells made more simply while the other shell is made with the complex design features, such as the features used to hold and align the internal circuit board and other components of the pluggable module. The simple shell may be manufactured from a less expensive manufacturing process, such as extrusion, while the complex shell may be manufactured from another process that allows the complex features to be formed, such as a die casting process. The different shells may be manufactured from different materials.

Unlike conventional pluggable modules that utilize an upper shell and a lower shell both having similar sizes and shapes, including a main, center wall and opposite side walls that extend approximately half way along the sides of the pluggable body meeting at a seam that is approximately centered between the upper and lower main walls, embodiments set forth herein have one of the shells made with all or substantially all of the sides while the other shell is generally only the main or center wall. For example, the upper shell may include the upper wall and both side walls, while the lower shell includes the lower wall extending between the side walls of the upper shell. The seam is thus positioned at the lower end of the pluggable body as opposed to at the approximate center, which is typical of conventional pluggable modules. The increased size of the upper shell makes the upper shell well suited for thermal transfer. The upper shell may be manufactured from a material having good thermal characteristics, such as copper or aluminum material.

FIG. 1is a perspective cross-sectional view of a communication system100in accordance with an embodiment. The communication system100may include a circuit board102, a receptacle assembly104mounted to the circuit board102, and one or more pluggable modules106that are configured to communicatively engage the receptacle assembly104. The communication system100is oriented with respect to a mating or insertion axis91, an elevation axis92, and a lateral axis93. The axes91-93are mutually perpendicular. Although the elevation axis92appears to extend in a vertical direction parallel to gravity inFIG. 1, it is understood that the axes91-93are not required to have any particular orientation with respect to gravity. Moreover, only one pluggable module106is shown inFIG. 1, but it is understood that multiple pluggable modules106may simultaneously engage the receptacle assembly104.

The communication system100may be part of or used with telecommunication systems or devices. For example, the communication system100may be part of or include a switch, router, server, hub, network interface card, or storage system. In the illustrated embodiment, the pluggable module106is configured to transmit data signals in the form of electrical signals. In other embodiments, the pluggable module106may be configured to transmit data signals in the form of optical signals. The circuit board102may be a daughter card or a mother board and include conductive traces (not shown) extending therethrough.

The receptacle assembly104includes a receptacle housing108that is mounted to the circuit board102. The receptacle housing108may also be referred to as a receptacle cage. The receptacle housing108may be arranged at a bezel or faceplate109of a chassis of the system or device such that the receptacle housing108is interior of the device and corresponding faceplate109and such that the pluggable module(s)106may be loaded into the receptacle housing108from outside or exterior of the device and corresponding faceplate109.

The receptacle housing108includes a front end110and an opposite back end112. The front end110may be provided at, and extend through an opening in, the faceplate109. The mating axis91may extend between the front and back ends110,112. Relative or spatial terms such as “front,” “back,” “top,” or “bottom” are only used to distinguish the referenced elements and do not necessarily require particular positions or orientations in the communication system100or in the surrounding environment of the communication system100. For example, the front end110may be located in or facing a back portion of a larger telecommunication system. In many applications, the front end110is viewable to a user when the user is inserting the pluggable module106into the receptacle assembly104.

The receptacle housing108is configured to contain or block electromagnetic interference (EMI) and guide the pluggable module(s)106during a mating operation. To this end, the receptacle housing108includes a plurality of housing walls114that are interconnected with one another to form the receptacle housing108. The housing walls114may be formed from a conductive material, such as sheet metal and/or a polymer having conductive particles. In the illustrated embodiment, the housing walls114are stamped and formed from sheet metal. In some embodiments, the receptacle housing108is configured to facilitate airflow through the receptacle housing108to transfer heat (or thermal energy) away from the receptacle assembly104and pluggable module(s)106. The air may flow from inside the receptacle housing108(for example, behind the faceplate109) to the external environment (for example, forward of the faceplate109) or from outside the receptacle housing108into the interior of the receptacle housing108. Fans or other air moving devices may be used to increase airflow through the receptacle housing108and over the pluggable module(s)106.

In the illustrated embodiment, the receptacle housing108includes a first (or bottom) row116of elongated module cavities120and a second (or top) row118of elongated module cavities122. Each of the module cavities120,122extends between the front and back ends110,112. The module cavities120,122have respective port openings121,123that are sized and shaped to receive a corresponding pluggable module106. The module cavities120,122may have the same or similar dimensions and extend lengthwise in a direction that is parallel to the mating axis91. In the illustrated embodiment, each module cavity122is stacked over a corresponding module cavity120such that the module cavity120is positioned between the module cavity122and the circuit board102. Any number of module cavities may be provided including a single module cavity.

In some embodiments, the pluggable module106is an input/output cable assembly having a pluggable body130. The pluggable body130includes a mating end132and an opposite cable end134. A cable136is coupled to the pluggable body130at the cable end134. The pluggable body130also includes an internal circuit board138that is communicatively coupled to electrical wires or optical fibers (not shown) of the cable136. The cable136may be communicatively coupled by directly terminating the wires to the internal circuit board138, such as by soldering the wires to the internal circuit board. Alternatively, the cable136may be communicatively coupled by other processes, such as by using connectors at the end of the cable136and on the internal circuit board138. The internal circuit board138is supported by the pluggable body130. The circuit board138includes contact pads140at the mating end132. InFIG. 1, the mating end132is configured to be inserted into the module cavity122of the receptacle housing108and advanced in a mating direction along the mating axis91. In an exemplary embodiment, the pluggable body130provides heat transfer for the internal circuit board138, such as for the components on the internal circuit board138. For example, the internal circuit board138is in thermal communication with the pluggable body130and the pluggable body130transfers heat from the internal circuit board138. In an exemplary embodiment, the heat is transferred from at or near the mating end132, such as where various electrical components are located on the internal circuit board138, to the cable end134. The heat is pulled out of the receptacle assembly104and mating end132and rejected to the external environment forward of the faceplate109. In other embodiments, the heat may be drawn into other portions of the pluggable body130and/or the heat may be directed to other portions of the pluggable body130, such as to the mating end132where the heat may be transferred to another heat sink or heat transferring component inside the chassis.

The receptacle assembly104includes a communication connector142having first and second mating interfaces144,146. The first mating interface144is disposed within the module cavity120, and the second mating interface146is disposed within the module cavity122. The first and second mating interfaces144,146are aligned with the port openings121,123, respectively. Each of the first and second mating interfaces144,146includes respective electrical contacts145,147that are configured to directly engage the contact pads140of the pluggable module106. Thus, a single communication connector142may mate with two pluggable modules106.

In alternative embodiments, the receptacle assembly104does not include the stacked module cavities120,122and, instead, includes only a single row of module cavities120or only a single module cavity120. In such embodiments, the communication connector142may have a single row of mating interfaces or a single mating interface.

The pluggable module106is an input/output (I/O) module configured to be inserted into and removed from the receptacle assembly104. In some embodiments, the pluggable module106is a small form-factor pluggable (SFP) transceiver or quad small form-factor pluggable (QSFP) transceiver. The pluggable module106may satisfy certain technical specifications for SFP or QSFP transceivers, such as Small-Form Factor (SFF)-8431. In some embodiments, the pluggable module106is configured to transmit data signals up to 2.5 gigabits per second (Gbps), up to 5.0 Gbps, up to 10.0 Gbps, or more. By way of example, the receptacle assembly104and the pluggable module106may be similar to the receptacle cages and transceivers, respectively, which are part of the SFP+ product family available from TE Connectivity.

Also shown inFIG. 1, the housing walls114of the receptacle housing108also form a separator plate148between the module cavities120,122. The separator plate148extends generally parallel to the mating axis91between the front end110and the back end112. More specifically, the module cavity120, the separator plate148, and the module cavity122are stacked along the elevation axis92. Optionally, a light-indicator assembly (not shown), such as a light pipe may be provided in the separator cavity defined by the separator plate148. The separator cavity may allow airflow between the module cavities120,122to enhance heat transfer from the pluggable modules106located in the module cavities120,122.

FIG. 2is a partially exploded view of the receptacle assembly104and illustrates the receptacle housing108and a plurality of the communication connectors142mounted to the circuit board102. In some embodiments, the receptacle housing108is formed from a plurality of interconnected panels or sheets. For example, the receptacle housing108includes a main panel or shell170that surrounds a housing cavity172, a plurality of interior panels174, a base panel181, and separator panels176defining the separator plate148. Each of the main panel170, the interior panels174, and the separator panels176may be stamped and formed from sheet metal. As described in greater detail below, each of the main panel170, the interior panels174, and the separator panels176may form one or more of the housing walls114that define the module cavity120, the module cavity122, and the separator plate148as shown inFIG. 1. As shown inFIG. 2, the main panel170includes an elevated wall180, sidewalls182,183, and a back wall184. The elevated wall180is located furthest from the circuit board102when the receptacle assembly104is constructed. The base panel181may rest on the circuit board102. The sidewalls182,183and the back wall184are configured to extend from the circuit board102, when mounted thereto, to the elevated wall180.

The interior panels174and the separator panels176are configured to be positioned within the housing cavity172. Within the main panel170, the interior panels174and the separator panels176apportion or divide the housing cavity172into the separate module cavities120,122(FIG. 1) and the separator cavity of the separator plate148(FIG. 1).

In the illustrated embodiment, each of the interior panels174has a panel edge191that interfaces with the elevated wall180and a panel edge192that interfaces with the base panel181and/or the circuit board102. The panel edge192may include mounting pins or tails194that are configured to mechanically engage and electrically couple to vias or thru-holes196of the circuit board102. The panel edge191may include tabs or latches197that are configured to be inserted through slots198of the elevated wall180to couple to the elevated wall180. Likewise, the sidewalls182,183and the back wall184may have panel edges193that include mounting pins or tails195configured to mechanically engage and electrically couple to corresponding vias196of the circuit board102.

The main panel170, the base panel181, the interior panels174, and the separator panels176may comprise conductive material, such as metal or plastic. When the receptacle housing108is mounted to the circuit board102, the receptacle housing108and the receptacle assembly104are electrically coupled to the circuit board102and, in particular, to ground planes (not shown) within the circuit board102to electrically ground the receptacle housing108and the receptacle assembly104. As such, the receptacle assembly104may reduce EMI leakage that may negatively affect electrical performance of the communication system100(FIG. 1).

FIG. 3is an exploded view of the pluggable module106in accordance with an exemplary embodiment.FIG. 4is a front perspective view of the pluggable module106in accordance with an exemplary embodiment. The pluggable body130holds the internal circuit board138. The pluggable body130has a first end200and an opposite second end202with sides204,206extending between the first and second ends200,202. The first and second ends200,202and the sides204,206extend lengthwise along a length208of the pluggable body130between the mating end132and the cable end134. The first end200, second end202and sides204,206define a cavity210that holds the internal circuit board138.

In an exemplary embodiment, the pluggable body130includes a first shell212and a second shell214. Optionally, the first shell212may define an upper shell and may be referred to hereinafter as upper shell212. The second shell214may define a lower shell and be referred to hereinafter as lower shell214. The upper shell212includes the first end200, which defines an upper end or top of the pluggable body130. The first shell212includes the sides204,206. Optionally, the first shell212may define the entire sides204,206. In various embodiments, the upper shell212may define a significant majority of the sides204,206.

The lower shell214includes the second end202, which may define a lower end or bottom of the pluggable body130. In various embodiments, the lower shell214may define portions of the sides204,206, such portions being less than the portions of the sides204,206defined by the upper shell212. For example, the upper shell212may be taller than the lower shell214and the lower shell214may be shorter than the upper shell212.

Optionally, the lower shell214may be nested in the upper shell212such that the second end202extends between the sides204,206. For example, in such embodiments, the sides204,206of the upper shell212may extend to the bottom of the pluggable body130. In other various embodiments, the lower shell214may cap the upper shell212such that the second end202extends below bottom edges of the sides204,206to close the space between the sides204,206. In such embodiments, the second end202may define a small portion of the sides204,206at the bottom of the pluggable body130.FIG. 4illustrates the lower shell214as such. The lower shell214is shown extending across the bottom of the first shell212. The bottom edges of the sides204,206rest on the second end202of the lower shell214. The second end202defines portions of the sides204,206of the pluggable body130; however the significant majority of the sides204,206are formed by the upper shell212.

As shown inFIG. 4, the cavity210has a center plane216centered between the first and second ends200,202. The sides204,206of the upper shell212extend beyond the center plane216, such as below the center plane216. As such, the upper shell212is provided both above and below the center plane216. The lower shell214is completely positioned on one side of the center plane216, namely below the center plane216.

The pluggable body130, defined by the upper and lower shells212,214, defines a perimeter218around the cavity210. In an exemplary embodiment, the upper shell212defines at least two-thirds of the perimeter218. For example, because all or substantially all of the sides204,206are defined by the upper shell212, the upper shell212comprises a majority of the perimeter218of the pluggable body130. Optionally, the sides of the upper shell212may comprise at least 90% of the sides204,206of the pluggable body130. In an alternative embodiment, the lower shell214may define the majority of the perimeter218. For example, in such embodiment, the lower shell214may define all or a significant majority of the sides204,206in addition to the second end202.

In an exemplary embodiment, the upper shell212is used for effective heat transfer from the internal circuit board138. The upper shell212is placed in thermal communication with the internal circuit board138. Heat generated by the internal circuit board138is drawn into the upper shell212and transferred therefrom. Having the upper shell212comprise a majority of the pluggable body130allows more heat to be transferred by the upper shell212than with conventional pluggable body shells, which are typically approximately half of the pluggable body130. For example, conventional pluggable body shells typically meet at a seam along the center plane216such that both the upper and lower shells form approximately equal portions of the sides204,206. Due to manufacturing tolerances and thermal expansion, some gaps may exist along the seam between the shells of conventional pluggable bodies, and these gaps reduce heat transfer from the upper shell to the lower shell. As such, with conventional pluggable bodies, only approximately half the pluggable body (for example, only the upper shell or only the lower shell) is used for heat transfer. In contrast, with the pluggable body130, having the upper shell212define significant portions of the sides204,206, which extend near or to the bottom of the pluggable body130(for example, significantly beyond the center plane216), more material and surface area is available for heat transfer. A greater amount of heat transfer is achieved using the enlarged upper shell212as compared to conventional shells of conventional pluggable bodies. In alternative embodiments, the lower shell214may be oversized compared to the upper shell212and the lower shell214may be used to transfer the majority of the heat generated by the pluggable module106rather than the upper shell212.

In an exemplary embodiment, the upper shell212is fabricated from a different material than the lower shell214. For example, the upper shell212may be fabricated from a material having a higher thermal conductivity than the material of the lower shell214. For example, the upper shell212may be manufactured from copper or aluminum, whereas the lower shell214is manufactured from a cheaper material or a material having different characteristics, such as zinc or another material. Using a material having a high thermal conductivity allows a more efficient transfer of heat from the internal circuit board.

In an exemplary embodiment, the upper shell212is manufactured by an extrusion process such that the upper shell212includes an extruded body222. The lower shell214may be manufactured from a different process, such as a die casting process, a machining process, a stamp and forming process of a sheet metal body, a layering build-up process, such as 3D printing, or another process. For example, the lower shell214may include a die cast body224. Extruding the upper shell212is a less expensive manufacturing process than some other processes, such as machining. Additionally, extrusion is a process that may be used on materials having high thermal conductivity. For example, some other processes, such as die casting, require additives or impurities in some materials, such as aluminum, which lowers the thermal conductivity of such material. Additionally, the porosity of the material from die casting may be higher, leading to a lower thermal conductivity of the material. As such, shells made by such die casting may be less effective at heat transfer than shells made from extrusion. The extrusion process creates a simple structure having generally flat walls or surfaces. The upper shell212has a substantially uniform cross-section along the length208. For example, the upper shell212may have a uniform cross-section along a majority of the length208. The substantially uniform cross-section may be made substantially uniform by an extrusion process where the body is pushed or drawn through a die having the desired cross-section. The extrusion process may define an extruded envelope for the extruded body222(for example, a shape) and the final upper shell212may be contained within the extruded envelope; however some grooves or slots may be formed in the extruded body222, such as for latching or securing to the lower shell214, while still defining the substantially uniform cross-section. Optionally, the extruded body222may have a uniform cross-section except for one or more grooves or slots formed therein used for securing the upper shell212to the lower shell214. While the upper shell212is extruded in the illustrated embodiment, the upper shell212may be manufactured by other processes in alternative embodiments, including a die casting process, a machining process, a stamp and forming process of a sheet metal body, a layering build-up process, such as 3D printing, or another process.

In contrast, the machining process or the die casting process allows more complex structures to be formed by having various features cast or formed into the lower shell214. For example, the die cast body224may have supporting features, alignment features, guide features and/or connection features for the internal circuit board138and/or for coupling the upper shell212to the lower shell214. For example, the die cast body224may include one or more pockets226that receive various electrical components228of the internal circuit board138. The die cast body224may include supporting elements230for supporting the internal circuit board138. The die cast body224may include alignment elements232for aligning the internal circuit board138within the cavity210and/or for aligning the upper shell212with the lower shell214for connection thereto. The die east body224may include securing features234used for securing the upper shell212to the lower shell214. For example, the securing features234may include threaded bores that receive threaded fasteners to secure the upper shell212to the lower shell214. Other types of securing features234may be provided in alternative embodiments, such as latches, clips, and the like for securing the upper shell212to the lower shell214. The die cast body224may include a cable support236for supporting and/or aligning the cable136with the die cast body224.

The die cast body224may be manufactured from any type of material that may be readily die cast. For example, the die cast body224may be manufactured from zinc, which is an easy metal to cast as zinc has high ductility, high impact strength and lower costs than some other metals. By providing all the internal cavity complexity of the pluggable body130into the lower shell214, the upper shell212can be manufactured more simply, by a process where the upper shell may be made with a predominantly uniform cross-section to reduce the cost and complexity of the upper shell212.

In the illustrated embodiment, the upper shell212includes support ribs240extending into the cavity210from the sides204,206. The support ribs240are used to capture the internal circuit board138between the lower shell214and the support ribs240. The support ribs240may be extruded with the extruded body222.

FIG. 5is a front perspective view of the pluggable module106showing the second shell214nested in the first shell212. The second end202extends between the sides204,206. In such embodiment, the sides204,206of the upper shell212extend to the bottom of the pluggable body130.

FIG. 6is a front perspective view of the pluggable module106showing the lower shell214comprising the vast majority of the pluggable body130. For example, the lower shell214includes all or substantially all of the sides204,206of the pluggable body130in addition to the second end202. The upper shell212includes the first end200capping the space between the sides204,206of the lower shell214. In the illustrated embodiment, the lower shell214is used for heat transfer. The lower shell214may include an extruded body manufactured from a copper or aluminum material. The upper shell212may include a die cast body manufactured from a zinc material. The internal cavity complexity, such as the features for aligning and supporting the cable136and internal circuit board138may be cast into the upper shell212, whereas the lower shell214may be extruded and have a uniform cross section along the length thereof.

FIG. 7is a front perspective view of the pluggable module106showing the upper shell212including a plurality of fins250. The fins250are used for heat transfer. The fins250extend lengthwise along the first end200; however the fins250may extend from the sides204,206and/or the second end202in addition to the first end200or in lieu of the first end200. The fins250may extend substantially the entire length of the pluggable body130.

It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Dimensions, types of materials, orientations of the various components, and the number and positions of the various components described herein are intended to define parameters of certain embodiments, and are by no means limiting and are merely exemplary embodiments. Many other embodiments and modifications within the spirit and scope of the claims will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

As used in the description, the phrase “in an exemplary embodiment” and the like means that the described embodiment is just one example. The phrase is not intended to limit the inventive subject matter to that embodiment. Other embodiments of the inventive subject matter may not include the recited feature or structure. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. §112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.