High speed, shielded cable assembly

Information

  • Patent Grant
  • 6261127
  • Patent Number
    6,261,127
  • Date Filed
    Monday, January 24, 2000
    24 years ago
  • Date Issued
    Tuesday, July 17, 2001
    23 years ago
Abstract
A cable assembly including a cable with at least one connector terminated to an end of the cable. The cable includes at least one pair of signal wires and a grounding member that extends the length of the cable. The signal wires and grounding member are terminated to a connector and specifically terminated to two signal terminals and one ground terminal of the connector. These wires are terminated to tail portions of the terminals which are enclosed in an insulative material that defines a body portion of the connector housing. The ground terminal has two contact portions that extend along the exterior of the connector housing body portion, while the signal terminals have contact portions that extend lengthwise of the connector housing. The signal terminal contact portions are enclosed within an extension of the connector housing and the extension and body portions are themselves enclosed in a metal grounding shell. The grounding shell engages the ground contacts at one end and has two contact arms integrally formed therewith that extend into the interior of the connector housing between the signal terminal contact portions.
Description




BACKGROUND OF THE INVENTION




The present invention relates generally to cable assemblies used in high speed data transmission, and more particularly to a cable assembly having an improved shielding structure.




In the field of high speed data transmission, the data signals must travel over their associated signal paths with a measure of assurance. This assurance often depends on the impedance of the signal path. While the impedance of electrical cables may be maintained to almost a constant value, drops and rises in impedance often occur at connector points on the cables, for example, where the cable is terminated to a connector and that connector is in turn engaged with another connector. The impedance of a connector that is terminated to a cable may differ significantly from the impedance of the cable as well as the impedance of an opposing connector. Adding shielding to the terminating connector assists in moderating any impedance mismatch, but the effectiveness of shielding such a connector depends largely on the physical structure of the connector. Certain connector structures are made with difficult configurations so that shielding all of the effective portions of the connectors is an expensive task. In other connectors, the structure of the connector prevents the establishment of reliable connections when the desired shielding is added to them.




The present invention is directed to a cable connector construction that overcomes the aforementioned disadvantages.




SUMMARY OF THE INVENTION




Accordingly, it is a general object of the present invention to provide a cable connector in high speed cable assemblies with a reliable connector structure and improved impedance values.




Another object of the present invention is to provide a connector in a cable assembly having a shielded enclosure that provides a shielding member in contact with ground members of the connector throughout the length of the connector, and which mechanically contacts the ground pins of the connector.




Yet another object of the present invention is to provide a shielded cable connector for termination to high speed cable assemblies, the connector having an insulative housing that houses at least two signal contacts and one ground contact, the connector having a shielding member that extends over substantially the entire exterior surface of the connector to thereby enclose the connector housing, the shielding member having at least one tang portion that defines the ground contact of the connector and extending from one end thereof, the shielding member being in contact with a cable ground contact at an opposite end of the connector housing.




Still another object of the present invention is to provide an improved cable connector in high speed applications, the connector having a housing formed from a body portion and an extension portion, the connector housing enclosing a pair of signal contacts which are terminated to associated signal wires of the cable, a shield that encloses the connector housing, the connector housing having at least one ground contact disposed thereon proximate to a rear end of the housing, the ground contact abuttingly engaging the shield, the shield having a tab member extending therefrom and into the interior of the connector housing at the extension portion thereof, the tab member projecting into the connector housing interior in a manner so as to engage a corresponding grounding pin of a pin header, the shield providing beneficial shielding for substantially the entire length of the connector.




It is still yet another object of the present invention to provide an improved cable connector having a connector housing, the connector housing having a body portion that is molded over tail portions of signal and ground terminals of the connector which are terminated to corresponding signal and ground wire leads of a multi-wire cable, the connector housing having an extension portion that extends forward from the body portion and enclosing the contact portions of the connector, while separating the contact portions with an intervening space, the connector having a shield member disposed on an exterior surface of the connector housing, the shield member extending over the connector housing body and extension portions, and wherein the shield member has a grounding contact portion that extends therefrom into the intervening space and aligned with the signal contact portions so as to engage a ground terminal of an opposing connector.




The present invention accomplishes these objects by way of its unique structure. In one principal aspect of the present invention, and as exemplified by the preferred embodiment thereof, a pair of signal leads of two signal wires of the cable are terminated to a pair of corresponding signal terminals of the connector, while the shielding wire of the cable is terminated to a ground terminal. These terminations all occur at tail portions of the signal and ground terminals and these terminations are enclosed within a first housing portion of the connector. This first housing portion is applied to the cable ends and the termination portions of the terminals by insert molding, for example, and this first housing portion provides a strain relief for the cable.




The ground terminal extends transverse to the longitudinal axis of the connector housing to one or more sides of the first housing portion, while the signal terminals extend lengthwise of the connector and extend out from the first housing portion to present their contact portions in opposition to an opposing connector. These signal terminal contact portions are enclosed within a second housing portion that extends from the body portion. the signal terminal contact portions are spaced apart from each other within the connector, as are enclosures of the second housing portion so that an intervening space is defined between both the signal terminal contact portions and their second housing enclosures.




A conductive shielding member is provided that, in effect, electrically encloses the connector by extending over both the first and second housing portions. In this regard, the shielding member extends over the exterior surfaces of the first and second housing portions so that it covers and provides shielding to the cable wire termination points to the signal terminal contact portions. The shielding member takes the form of a hollow, metal sleeve, in the preferred embodiment and it contacts the ground terminal of the connector near the rear of the connector. The leading edge of the shielding member may be slotted to provide one or more legs, or tangs that extend from opposite sides into the intervening space between the two signal terminal contact portions and their enclosures. Ground shielding is therefore effected over the entire length of the connector.




In another aspect of the present invention, the shielding member will include a pair of grounding legs that extend inwardly in order to engage a ground pin of an opposing connector, such as a pin header in order to provide a reliable mechanical grounding contact with the grounding pin. This connection ensures shielding along the entire length of the connector housing. This provides approximately 150 ohms impedance with a variance of about +/−10 ohms at 250 ps rise times.




These, and other objects and advantages will become apparent from the following detailed description when taken in conjunction with the following drawings.











BRIEF DESCRIPTION OF THE DRAWINGS




In the course of the following detailed description reference will be frequently made to the accompanying drawings in which:





FIG. 1

is a plan view of a cable assembly constructed in accordance with the principles of the present invention;





FIG. 2

is an exploded plan view of the connector end of the cable assembly of

FIG. 1

;





FIG. 3

is a perspective view of a pin header in which the cable assembly of the present invention is used, illustrating the header in place on a circuit board;





FIG. 4

is a cross-sectional view of the pin header of

FIG. 3

taken along lines


4





4


thereof;





FIG. 5

is an exploded perspective view of the cable connector used in the cable assembly of

FIG. 1

, illustrated in alignment with a pin header;





FIG. 6A

is a cross-sectional view of a cable connector engaged in place within a pin header taken along a line approximately coincident with a ground pin of the pin header;





FIG. 6B

is a cross-sectional view similar to

FIG. 6A

, but taken along a line approximately coincident with a signal pin of the pin header;





FIG. 7

is a cross-sectional view of the cable of

FIG. 1

taken along lines


7





7


thereof;





FIG. 8

is an end view of the cable connector of

FIG. 1

, taken along lines


8





8


thereof;





FIG. 9A

is a perspective view of a ground terminal used in the connectors of the present invention; and,





FIG. 9B

is a perspective view of a signal terminal used in the connectors of the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS





FIG. 1

illustrates a cable assembly


20


constructed in accordance with the principles of the present invention. This cable assembly


20


can be seen to include an elongated cable


21


with two connectors


22


terminated to opposing ends of the cable


21


. The construction of the cable


21


is conventional in that, as shown in

FIG. 8

, it includes a pair of signal wires


25


,


26


, and preferably the wire pair includes a differential pair of signal wires that may extend for the length of the cable


21


and which may be twisted together along their length as shown in FIG.


1


. The cable signal wires


25


,


26


have a ground or drain wire


27


associated therewith, that typically takes the form of either a braided metal shield or a metal type wrapped around the signal wires


25


,


26


. This assembly is then enclosed within an insulative outer layer


28


. Whatever structure the ground wire


27


takes, it extends for substantially the entire length between the two opposing ends


29


of the cable


21


.




Turning now to

FIGS. 6A&6B

, the ends


29


of the cable


21


are trimmed to expose leads of the signal wires


25


,


26


and the shielding braid


27


for termination to the connector. The leads


31


of these signal wires


25


,


26


are connected to termination tails


41


of the signal terminals


40


of the connector


21


, with two such signal contacts being illustrated. Although only a pair of signal terminals


40


are illustrated and the invention is described in terms thereof, it will be understood that the present invention is not limited to connectors and cable assemblies utilizing only two signal terminals. A greater number of terminals may be used and the shielding member may be modified to accommodate grounding with respect to these signal wires.




The signal terminals


40


may be stamped and formed from a conductive material and may be of a receptacle-type construction, i.e., having a hollow contact portion


42


that is adapted to receive therein a conductive signal pin


37


of an opposing connector. The hollow contact portion


42


illustrated in the drawings is of a box-style terminal construction having four distinct sides to its receptacle. However, it will be understood that other style of receptacles may also be used, such as round, hollow receptacles. In most applications of the present invention, the opposing connector will be a pin header


34


. Such a pin header


34


is illustrated best in

FIGS. 5&6

, wherein it can be seen that the pin header


34


includes an insulative body portion


35


with a hollow interior portion that defines a receptacle


36


that is adapted to receive the connectors


22


of the present invention. The pin header


34


further includes a plurality of conductive signal pins


37


and at least one grounding pin


38


disposed in an array within the header receptacle


36


. These pins


37


,


38


extend through a base portion


39


of the header


34


that is mounted on a circuit board


23


(

FIG. 3.

) and they may extend through associated mounting openings or holes formed therein.




The terminals


40


have a preselected length and may be seen to include termination portions


41


, in the form of tails to which exposed leads


31


of the signal wires


25


,


26


of the cable are attached. This attachment may be effected by any conventional means, such as soldering or welding. The grounding wire


27


of the cable


21


also has a lead


32


prepared by unbraiding the individual wires that make up the shielding wire


27


. This lead


32


is likewise attached to a termination portion, or tail


45


. The grounding terminal


43


of the connector may take the form of a grounding strap


47


, having one or more contact portions


44


extending away at an angle from the tail


45


to an exterior location on the connector body


50


.




As shown in

FIG. 9A

, the ground terminal


43


includes a conductive strap portion


47


that forms part of the body, or base


60


, of the ground terminal


43


. This base


60


has two contact portions


44


that extend or diverge outwardly from the point where the tail portion


45


of the ground terminal


43


meets the base


60


. These two contact portions


44


are dimensioned so as to extend along the outer surface


53


of the connector body portion


50


. As so presented, the contact portions


44


extend along the body portion


50


as illustrated best in

FIG. 5

in a manner where they are easily contacted by the shield


75


of the connector


22


.




Turning now to

FIGS. 2&5

, the connector


51


can be seen to be cooperatively formed from two components. One such assembly component is the connector body portion


50


that is formed from an insulative material around the tail portions of the terminals


40


,


43


of the connector. In this regard, after the wires


25


-


27


of the cable are stripped and attached respectively to the signal terminal tail portions


41


and the ground terminal tail portion


45


to form a terminal-cable assembly, the assembly is inserted into a mold and insulative material, such as a plastic or nylon or other dielectric material may then be injected into the mold to mold the connector housing body portion


50


over the terminal tail portions


41


&


47


and the end


30


of the outer cable insulation covering


28


.




This material completely fills the mold and forms the body portion


50


, which, due to its location (

FIG. 6A

) provides strain relief to the cable and the termination ends of the cable wires.




This body portion preferably only encompasses the tail portions of the terminals


41


,


45


and does not contact the contact portions


42


,


44


of the terminals. This is illustrated best in

FIG. 5

, where it can be seen that the hollow receptacle portions


46


of the signal terminal contact portions


42


extend outwardly and forwardly from the body portion


50


of the connector


22


, while the ground terminal contact portions


44


extend out from the body portion and also forwardly along the body portion exterior surface


53


. The leading edge


52


of the body portion


50


defines an abutment surface that mates with, and may be considered in some instances to support an extension portion


55


of the overall connector housing.




This extension portion


55


is illustrated in

FIGS. 2&5

and it can be seen to include a pair of hollow members, such as tubes


56


that extend lengthwise of the connector for a preselected distance. These two tubes


56


include a central cavity


57


that communicates with a leading face


63


thereof and which, as explained below, houses a signal terminal contact portion


42


. The center cavities


57


communicate with the exterior by way of openings


58


disposed along the face


63


of the extension portion


55


so that the contact portions


43


of the signal terminal


40


may be contacted by opposing, conductive signal pins


37


of an opposing connector


34


. In the embodiment illustrated, the hollow tubes


56


are shown as resembling elongated boxes to accommodate the box-style receptacle terminals


40


, but it will be understood that other shapes, preferably ones that are similar to the signal terminals


40


may be utilized, such as hollow cylindrical tubes.




These extension tubes


56


substantially encompass the receptacle contact portions


42


of the signal terminals


40


and so insulate them from the exterior shield


75


of the connector. The leading edges


63


of the hollow tubes


56


preferably are aligned with the faces


70


of the signal terminal contact portions


42


, as shown best in FIG.


6


B. This alignment assists in protecting the signal terminals


40


and insulating them from contact with the outer shield


75


. As shown in the drawings, the extension portion


55


may be formed as a separate member from the boy portion


50


, but it may also be formed together with the body portion as a single piece, or as an assembly of half portions or the like that are assembled together to form the completed connector housing. The extension portion


55


further includes a slot


64


disposed between the two tubes


56


that defines an intervening space that extends rearwardly between the two tubes


56


. This slot


64


extends lengthwise of the connector


22


.




In an important aspect of the present invention, the connector


22


is provided with a conductive shield member


75


, illustrated in the drawings as a hollow metal shell


76


, having an elongated body portion that extends between first and second ends


77


,


78


thereof. The shell


76


preferably has a length S that is at least equal to or slightly greater than a corresponding length of the connector housing


51


, that is, the length C of the connector body portion


50


and extension portion


55


combined. With this length, the shield


75


substantially encompasses the connector housing and the signal terminals


40


contained therein in order to maintain a more uniform impedance value throughout the length of the connector and reduce any drop in impedance that may occur.




The shield


75


has an interior cavity with an inner conductive surface that opposes and overlies the contact portions


44


of the ground terminal


43


. In this manner, when the shell


76


is slipped over the body portion


50


, the ground terminal contact portions


44


will slide upon and abut the inner surface


84


of the shell


76


, thereby establishing electrical contact between the shell and the grounding member


27


of the cable


21


. The shell


76


further encloses the extension portion


55


and the two signal terminals


40


that they enclose in the tube portions


56


thereof. Preferably the leading edge


81


of the shell


76


extends slightly past (or forward in the drawings) the leading faces


63


of the tubes so that the shell


76


will also serve to protect the ends of the receptacle contacts of the signal terminal


40


. This is shown by distance L in

FIGS. 6A and 6B

. In order to provide a ground connection through the length of the connector, the shield


75


is also provided with at least one ground contact


82


disposed at a second end


78


thereof. This ground contact is shown as being integrally formed with the body portion of the shell


76


, such by being stamped from the shell


76


and proximate to the leading edge


81


thereof.




As shown best in

FIGS. 5&6A

, this ground contact


82


depends downwardly into the interior cavity of the shell


76


. In this disposition, the ground contact


82


also extends into the extension portion slot


64


and into the intervening space between the two tube members


56


of the extension. A second ground contact


83


may be formed in the shell


76


along an opposite surface thereof, shown as the bottom surface thereof. This second ground contact


83


is preferably also stamped from the leading edge


81


of the shell


76


and is also aligned with the first ground contact


82


in a vertical plane. In this manner, the two ground contacts


82


,


83


each have a contact area


85


that oppose each other and which further contact opposite sides of a grounding pin


38


of an opposing connector


34


. The contact areas


85


of the two ground contacts


82


,


83


may be aligned with the faces


89


of the receptacle contacts


42


or may be offset forwardly as illustrated so that the ground contacts


82


,


83


will engage the grounding pin


38


of the opposing connector


34


before the signal terminals


40


do, i.e., “make first”, and will also disengage from the grounding pin


38


after the signal terminals have disengaged, i.e., “break last”.




Furthermore, the overall configuration of the shell


76


may be specifically configured so as to provide a polarizing means to ensure that the connector


21


may engage an opposing connector


34


in only one fashion. In the embodiment illustrated, this polarizing feature is provided by chamfered edges


72


that mate with chamfered corners


73


of the receptacle of the opposing connector


34


. The shell


76


may also be provided with a latching, or engagement member


90


that is stamped out of the shell so that it is raised with respect to the rest of the shell profile. This latching member engages an opening


91


formed in the opposing connector


34


.




While the preferred embodiments of the invention have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made to these embodiments without departing from the spirit of the invention, the scope of which is defined by the appended claims.



Claims
  • 1. A cable assembly particularly suitable for high-speed applications, comprising:an elongated cable having at least two signal wires and a grounding member extending for a length of the cable, said signal wires and grounding member being enclosed within an outer insulative wire covering of said cable, a connector terminated to at least one end of said cable, the connector including an insulative housing and at least two conductive signal terminals, each of the signal terminals including a contact portion and a tail portion, said signal wires being terminated to said signal terminal tail portions, said connector further including a ground terminal having at least one contact portion and a tail portion, the grounding member of said cable being terminated to said ground terminal tail portion, the connector housing including an extension enclosing said signal terminal contact portions, and said connector further including a conductive shield member having first and second ends interconnected by a body portion, the shield member extending over said connector housing such that said ground terminal contact portion conductively contacts said shield member to electrically connect said cable grounding member to said shield member, and said shield member having at least one ground contact portion formed therewith and extending therefrom between portions of said extension, said shield ground contact being formed proximate to said first end of said shield and said ground terminal contact portion contacting said shield proximate to said second end of said shield; and wherein said shield member includes a hollow metal shell with an interior cavity that extends through said shell between said first and second ends thereof, said shell overlying said ground terminal contact portion and having a conductive interior surface that contacts said ground terminal contact portion, said ground contact formed therein proximate to said second end thereof, said ground contact and second ground contact extending into said interior cavity of said shell between portions of said extensions.
  • 2. The cable assembly as set forth in claim 1, wherein said extension includes a body with a pair of hollow passages, each of the passages enclosing a signal terminal contact portion, said hollow passages being spaced apart from each other by an intervening space, and said shield ground contact extending into said intervening space.
  • 3. The cable assembly as set forth in claim 1, wherein said signal terminal contact portions extend for a preselected length and include end portions presented in opposition to signal terminals of an opposing connector, the end portions being spaced rearwardly from said shield second end such that said end portions do not protrude past said shield second ends.
  • 4. The cable assembly as set forth in claim 1, wherein said shield includes a second contact portion formed in opposition to said ground contact.
  • 5. A cable assembly particularly suitable for high-speed applications, comprising:an elongated cable having at least two signal wires and a grounding member extending for a length of the cable, said signal wires and grounding member being enclosed within an outer insulative wire covering of said cable, a connector terminated to at least one end of said cable, the connector including an insulative housing and at least two conductive signal terminals, each of the signal terminals including a contact portion and a tail portion, said signal wires being terminated to said signal terminal tail portions, said connector further including a ground terminal having at least one contact portion and a tail portion, the grounding member of said cable being terminated to said ground terminal tail portion, the connector housing including an extension enclosing said signal terminal contact portions, and said connector further including a conductive shield member having first and second ends interconnected by a body portion, the shield member extending over said connector housing such that said ground terminal contact portion conductively contacts said shield member to electrically connect said cable grounding member to said shield member, and said shield member having at least one ground contact portion formed therewith and extending therefrom between portions of said extension, said shield ground contact being formed proximate to said first end of said shield and said ground terminal contact portion contacting said shield proximate to said second end of said shield; and wherein said housing extension includes a pair of hollow tubes, each of the tubes extending longitudinally of said connector housing and enclosing a signal terminal contact portion therein, said hollow tubes being spaced apart by an intervening space, and each of said hollow tubes including an opening facing in the same direction as shield second end, and wherein said shield member includes a hollow, metal shell having an interior cavity that extends completely through said shell between said first and second of said shield member, said shell having a conductive interior surface that overlies and contacts said ground terminal contact portion and which also overlies said tubes, said shell further having a ground contact formed therein proximate to said shield member second end thereof, ground contact extending into said interior cavity of said shell and between said tubes.
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