United States Patent [19J
`Meyer et al.
`
`I lllll llllllll Ill lllll lllll lllll lllll lllll 111111111111111111111111111111111
`US005915995A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,915,995
`Jun.29,1999
`
`[54] DUAL CONTACT BANANA CONNECTOR
`
`[75]
`
`Inventors: Daniel B. Meyer, Lake Oswego;
`Clifford E. Baker, Hillsboro, both of
`Oreg.
`
`[73] Assignee: Tektronix, Inc., Wilsonville, Oreg.
`
`[21] Appl. No.: 08/988,500
`
`[22] Filed:
`
`Dec. 10, 1997
`
`Int. Cl.6
`..................................................... HOlR 17/18
`[51]
`[52] U.S. Cl. ............................................. 439/668; 439/585
`[58] Field of Search ..................................... 439/668, 825,
`439/660, 585, 172, 169, 527, 502, 101,
`188, 669
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,325,599
`4,988,315
`5,022,872
`5,147,221
`
`4/1982 Feldman .............................. 339/103 R
`1/1991 Whaton ................................... 439/668
`6/1991 Shichida .................................. 439/668
`9/1992 Cull et al. ............................... 439/585
`
`5,230,641
`5,704,812
`
`7/1993 Wharton ....... ... ......... .... ........... 439/668
`1/1998 Moji ........................................ 439/668
`
`FOREIGN PATENT DOCUMENTS
`
`1510-031-A
`WO 93/08623
`
`9/1989 U.S.S.R ................................. 439/668
`4/1993 WIPO .................................... 439/668
`
`Primary Examiner-Steven L. Stephan
`Assistant Examiner-Michael C. Zarroli
`Attorney, Agent, or Firm-Bennet K. Langlotz; William K.
`Bucher
`
`[57]
`
`ABSTRACT
`
`An electrical connector with a female portion defining a bore
`having an aperture, and a male portion having an elongated
`member sized to be received in the bore. The female portion
`has a first flexible contact and an electrically isolated second
`rigid contact. The male portion has a first flexible contact
`and an electrically isolated second rigid contact. The con(cid:173)
`nector may be a banana connector with a barrel spring
`providing conventional contact, and a separate contact at the
`tip of the male portion.
`
`5 Claims, 3 Drawing Sheets
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`14
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`--12
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`10
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`32
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`44
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`'1
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`(cid:20)(cid:19)(cid:24)(cid:26)
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`U.S. Patent
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`Jun.29,1999
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`Sheet 1of3
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`5,915,995
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`14
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`......---12
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`10
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`32
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`44
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`s2
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`FIG.1
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`U.S. Patent
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`Jun.29,1999
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`Sheet 2 of 3
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`5,915,995
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`14
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`/ 1 2
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`20
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`30
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`28
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`62
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`FIG.4
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`104
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`24
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`60
`FIG.2
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`U.S. Patent
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`Jun.29,1999
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`Sheet 3 of 3
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`5,915,995
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`85
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`82
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`16
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`)
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`FIG.3
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`5,915,995
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`1
`DUAL CONTACT BANANA CONNECTOR
`
`FIELD OF THE INVENTION
`
`The invention relates to electrical connectors, and more
`particularly to connectors having multiple independent con(cid:173)
`tacts on a single connector.
`
`BACKGROUND AND SUMMARY OF THE
`INVENTION
`
`Electrical connectors are used for interconnecting elec(cid:173)
`tronic instruments or components. A typical connector is a
`banana lead having a single wire terminated at each end with
`a male banana plug. The banana plug has an elongated
`conductive probe portion wrapped with barrel spring, so that
`the probe portion may be inserted into a female receptacle in
`an instrument, with a conductive sleeve in the receptacle
`making contact with the barrel spring. Many other connector
`types have multiple lines, with multiple contacts on each end
`of a lead. Others have shielded configurations that have a
`signal wire wrapped by a shield wire, and coaxial end
`connectors to maintain shielding at the connections.
`Instruments generally have limited area available for
`connector receptacles on exposed face plates. It is often
`desirable for an instrument to accept different connectors for
`different purposes. However, the different connector con(cid:173)
`figurations require different types of connector receptacles,
`which increases the number of receptacles needed for ver(cid:173)
`satility. For instance, a set of single receptacles may be
`needed in addition to a set of multiple-line connector recep- 30
`tacles. Lacking compatibility, an increased number of
`receptacles, and therefore an increased panel area must be
`provided.
`The embodiments disclosed herein overcome these limi(cid:173)
`tations by providing an electrical connector with a female 35
`portion defining a bore having an aperture, and a male
`portion having an elongated member sized to be received in
`the bore. The female portion has a first flexible contact and
`an electrically isolated second rigid contact. The male por-
`tion has a first flexible contact and an electrically isolated
`second rigid contact. The connector may be a banana
`connector with a barrel spring providing conventional
`contact, and a separate contact at the tip of the male portion.
`
`40
`
`2
`shape in several sections. A shroud section 22 terminates at
`a free end 24 of the plug. The shroud is a thin walled cylinder
`that protects an elongated conductive plug element 26
`coaxially received therein. A grip section 28 of the housing
`has a textured or ribbed outer surface, and a strain relief
`portion 30 defines perforations to permit flexure, and pro(cid:173)
`vides a passage for the lead 14.
`The plug element 26 includes an elongated metal body 32
`defining a bore 34. A cylindrical portion 36 of the body
`10 extends from a flange portion 40 toward the free end 24 of
`the plug. The flange rests against a shoulder in the plug
`housing bore, and has a butt portion 42 extending partly into
`the grip section 28. A barrel spring 44 is closely received on
`the cylindrical portion 36, and has elongated spring elements
`15 46 that are positioned against the surface of the cylindrical
`portion at their ends, and which curve slightly so as to bulge
`outward at their midsections, in the manner of a conven(cid:173)
`tional barrel spring on a banana plug.
`The plug body bore 34 includes an enlarged end bore
`20 portion 50 near the free end. The end bore portion receives
`a plastic sleeve 52 defining a bore smaller than, and coaxial
`with the body bore 34. The sleeve has an enlarged rim 54
`that limits insertion of the sleeve into the bore, and which
`has an outside diameter larger than the end portion of the
`25 metal body 32.
`Arigid conductive nail 56 having an enlarged head 60 and
`an elongated shank 62 is received in the bore 34. The shank
`extends fully through the bore, with a protruding portion 64
`extending beyond the end of the butt portion 42 of the body
`within the grip portion of the housing. The head portion of
`the nail rests against the rim 54 of sleeve 52, and has a
`diameter approximately equal to the rim diameter, a length
`less than half its diameter, and quarter-radius ed peripheral
`edges. The nail may have an insulative coating on the shaft
`to prevent electrical contact with the plug body bore near the
`protruding end. The free end of the nail is recessed from the
`free end 24 of the housing, so that contact by a fingertip is
`prevented.
`Lead wire 14 has two conductive wires 66, 70. Wire 66 is
`electrically connected to a conductive shroud that fills and
`rigidly supports the grip section of the flexible plug housing,
`and which is crimped about the butt portion 42 of the
`conductive plug body. Wire 70 is connected to the protrud-
`45 ing end 64 of the nail 56.
`FIG. 3 shows the female receptacle portion 16 mounted in
`a hole 72 of a printed circuit board 74 of an instrument. The
`receptacle is a stout cylindrical body formed of rigid insu(cid:173)
`lative plastic, and having cylindrical exterior surface 76
`50 having several ribs running partially along the length, and
`terminating at shoulders 80, which are positioned against the
`board surface. The receptacle defines a central bore 82 and
`an annular bore 84 coaxial with the central bore and extend(cid:173)
`ing nearly the full length of the receptacle. A cylindrical
`55 protrusion having a free end 85 defines bore 82, and is
`surrounded by bore 84.
`Two independent electrical contacts reside in the recep(cid:173)
`tacle bore. A rigid conductive sleeve contact 86 is closely
`received by a major portion of the bore, and has a sleeve end
`60 90 positioned against a shoulder in the bore. The sleeve
`defines a sleeve bore 92 having a diameter slightly less than
`that of an end portion 94 of the receptacle bore. The sleeve
`extends a substantial depth into the bore, so that a standard
`male banana connector makes contact when inserted.
`The receptacle bore includes an enlarged chamber 96 at its
`deepest portion. The chamber is enclosed at its base by a
`cover plate 100 that is absent during installation of the
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a perspective view of a connector pair according
`to a preferred embodiment of the invention.
`FIG. 2 is a sectional side view of a male element of the
`connector pair of FIG. 1.
`FIG. 3 is a sectional side view of a female element of the
`connector pair of FIG. 1.
`FIG. 4 is a sectional side view of the connector pair of
`FIG. 1 in a mated condition.
`
`DETAILED DESCRIPTION OF A PREFERRED
`EMBODIMENT
`
`FIG. 1 shows a split or dual banana connector pair 10
`having a male portion or plug 12 connected to a lead 14, and
`a female portion or receptacle 16 for connection to an
`instrument panel, chassis, or printed circuit board, as will be
`discussed below. The lead connects to a probe (not shown)
`that contacts a device being tested by the instrument in
`which the female receptacle is mounted.
`FIG. 2 shows the male plug in greater detail. The plug has
`a plastic insulative housing 20 that has an elongated tubular
`
`65
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`5,915,995
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`3
`sleeve, then installed and secured to enclose the bore. A
`flexible conductive spring 102 is mounted to the interior
`surface of the cover 100. The spring has a fiat base mounted
`to the cover, and a pair of opposed arms extending upward
`from the base. The spring arms are nearly parallel leaf
`springs, slanting slightly toward each other. At their free
`ends, the springs are curved away from each other to
`facilitate smooth insertion of a plug element between the
`arms. The spring arms are straight until the end flares, and
`the point of inflection 104 approximately forms the narrow- 10
`est spacing between the spring arms when at rest. Each of the
`sleeve contact 86 and the spring contact 102 is electrically
`connected to the board 74 or to other electrical circuitry in
`the instrument.
`FIG. 4 shows the male and female sections of the plugs
`mated for electrical connection of each of the lead lines to
`the instrument. Fully mated, the free end 85 of the receptacle
`protrusion rests against the shoulder 40 of the plug body. The
`shroud 22 is received in the annular bore 84. The plug body
`32 is fully inserted into the central bore, with the widest
`portions of the barrel spring elements aligned with an
`intermediate position of the sleeve 86. The free ends of the
`spring arms 102 extend to a distance aligned with the end of
`the plug body; due to the outward flare of the free ends,
`contact between the spring and the body is avoided. As the 25
`diameter of the nail head 60 is approximately equal to the
`length of the spring base, insertion of the head between the
`spring arm ends to a depth slightly beyond the inflection
`points 104 spreads apart the arms to a parallel configuration.
`This further flares spring free ends away from the plug body, 30
`and ensures contact with the nail head instead of with the
`plug sleeve 52. The contact with the barrel spring provides
`a high current capacity main contact, which the contact with
`the nail head is well suited to a lower current signal or logic
`line.
`In the preferred embodiment, the dimensions of many of
`the connector elements are compatible with or the same as
`those of a conventional standard banana plug connector
`according to military specification A-A-55468; the plug's
`nail head contact and the associated receptacle spring 102
`are departures from the standard connector. In the preferred
`embodiment, the cylindrical portion 36 of the plug body 32
`has a length of 0.730 inch, a minimum barrel-spring(cid:173)
`compressed diameter of 0.160 inch, a maximum diameter
`about the uncompressed barrel springs of 0.180 inch, with 45
`the widest spring point spaced 0.413 inch from the shoulder
`40. The barrel spring has a length of 0.475 inch, so that it is
`spaced apart from the shoulder by 0.170 inch. To provide
`room for the insulative sleeve and the nail head contact in
`the preferred embodiment's standard length, the cylindrical 50
`portion 36 of the plug body extends only to 0.645 inch from
`
`35
`
`40
`
`4
`the shoulder, with the sleeve rim adding another 0.040 inch,
`and the nail head adding a final 0.045 inch.
`The nail head has a diameter of 0.150 inch, and the sleeve
`rim has a flange diameter of 0.145 inch. In the receptacle, the
`sleeve 86 has a length of 0.410 inch, and is spaced apart from
`the free end 85 of the receptacle by 0.160 inch. The sleeve
`has an inside diameter of 0.160 inch.
`By using the standard banana plug specifications, either
`portion of the disclosed connector may be used as or in
`conjunction with a standard single plug banana plug or
`receptacle. The second nail head/receptacle spring contacts
`may be idle while the primary barrel spring/sleeve contact is
`used. Thus, a single receptacle on an instrument panel may
`serve as a two line or split connection, as might be used for
`15 a thermocouple or shielded signal lead, while also serving as
`a receptacle for a conventional banana lead for other pur(cid:173)
`poses. This versatility reduces the number of receptacles
`required for a given number of dual and single connections.
`While the disclosure is made in terms of a preferred
`20 embodiment, the invention is not intended to be so limited.
`We claim:
`1. An electrical connector comprising:
`a female portion defining a bore having an aperture;
`a male portion having an elongated member sized to be
`received in the bore and having a free end;
`the male portion having an elongated electrically conduc(cid:173)
`tive body defining a bore with a free end and having a
`first flexible barrel spring contact on the body and an
`insulating sleeve having a bore therein that is disposed
`in the free end of the elongated electrically conductive
`body bore that receives a second rigid electrical contact
`extending within the bore of the elongated electrically
`conductive body and forms a separate contact at the
`free end tip of the male portion; and
`the female portion having a first flexible contact and an
`electrically isolated second rigid sleeve contact sized to
`receive the barrel spring.
`2. The connector of claim 1 wherein the rigid contact of
`the male portion is at the free end of the elongated member.
`3. The connector of claim 2 wherein the flexible contact
`of the female portion is a spring positioned in the bore at a
`greater depth than the depth at which the female rigid
`contact is positioned, such that the male rigid contact
`contacts only the female flexible contact.
`4. The connector of claim 1 wherein the female portion
`flexible contact includes a leaf spring.
`5. The connector of claim 1 wherein the female portion
`rigid contact is closer to the female portion flexible contact
`than to the aperture of the bore.
`
`* * * * *
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