U.S. patent application number 10/422883 was filed with the patent office on 2003-10-16 for miniature retractable cord reel.
This patent application is currently assigned to TELEFONIX, INC. Invention is credited to Burke, Paul C., Skowronski, Richard E..
Application Number | 20030192760 10/422883 |
Document ID | / |
Family ID | 25323077 |
Filed Date | 2003-10-16 |
United States Patent
Application |
20030192760 |
Kind Code |
A1 |
Burke, Paul C. ; et
al. |
October 16, 2003 |
Miniature retractable cord reel
Abstract
A cord reel device for connecting a signal source to remote
device comprises a spool rotatable on an arbor, the spool having an
inner chamber and an outer trough. A retractable cord is removably
held in the trough. A spring for urging rotation of the spool in a
direction to retract the cord is held in the inner chamber. An
inner cable is wound with the spring in the spool inner chamber.
The inner cable is electrically connected to the retractable cord.
The cord reel of the invention may preferably include EMI-RFI
shielding, and may find particular utility in applications
requiring a substantially miniature cord reel, such as with a
cellular telephone or the like.
Inventors: |
Burke, Paul C.; (Lake
Forest, IL) ; Skowronski, Richard E.; (North Hampton,
NH) |
Correspondence
Address: |
Mark G. Hanley
GROSSMAN & FLIGHT, LLC
Suite 4220
20 North Wacker Drive
Chicago
IL
60606
US
|
Assignee: |
TELEFONIX, INC,
|
Family ID: |
25323077 |
Appl. No.: |
10/422883 |
Filed: |
April 23, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10422883 |
Apr 23, 2003 |
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09856214 |
Sep 24, 2001 |
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6578683 |
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09856214 |
Sep 24, 2001 |
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PCT/US99/26711 |
Nov 12, 1999 |
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PCT/US99/26711 |
Nov 12, 1999 |
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09197326 |
Nov 20, 1998 |
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Current U.S.
Class: |
191/12.4 |
Current CPC
Class: |
H02G 11/02 20130101;
H04M 1/15 20130101 |
Class at
Publication: |
191/12.4 |
International
Class: |
H02G 011/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2000 |
WO |
00/31847 |
Claims
What is claimed is:
1. A retractable cord reel rotatable on an arbor, comprising: a) a
spool, rotatably mounted on the arbor, said spool having an annular
wall defining an outer trough and an inner chamber, said spool
having a diameter of less than about 4 cm; b) a retractable cord
removably held in said outer trough; c) means attached to said
spool for rotating said spool in a cord retracting direction; and
d) an inner cable in said spool inner chamber, said inner cable
connected to said retractable cord.
2. A retractable cord reel as in claim 1, wherein said rotating
means comprises a spring in said spool inner chamber, said inner
cable helically wound with said spring, said spring having one end
attached to the arbor and the other end attached to said spool.
3. A retractable cord reel rotatable on an arbor, comprising: a) a
spool, rotatably mounted on the arbor, said spool having an annular
wall defining an outer trough and an inner chamber; b) a
retractable cord removably held in said outer trough; c) a spring
coiled in said spool inner chamber, one end of said spring attached
to the arbor and the other end of said spring attached to said
spool, said spring for rotating said spool in a cord retracting
direction; and d) an inner cable in said spool inner chamber,
helically wound with said spring, said inner cable connected to
said retractable cord.
4. A retractable cord reel as in claim 3, wherein said spool is
shielded.
5. A retractable cord reel as in claim 3, the cord reel
electrically connecting a source to a remote device, a portion of
said inner cable having extending axially out of the reel at the
arbor for connection to the source, said retractable cord being
connected to the remote device.
6. A retractable cord reel as in claim 3, further comprising a
housing for containing said spool, said housing having a radial
opening through which said retractable cord passes.
7. A retractable cord reel as in claim 3, further comprising a
ratchet operatively engaged with said spool for selectively
restraining rotation of said spool.
8. A retractable cord reel as in claim 3, wherein said retractable
cord and said inner cable are unitary.
9. A retractable cord reel as in claim 3, wherein said retractable
cord comprises an outer jacket and at least one inner conductor,
said outer jacket attached to said spool.
10. A retractable cord reel as in claim 3, wherein said retractable
cord comprises plural conductors and a shield layer surrounding at
least one of said conductors; said inner cable comprises plural
conductors, each connected to a respective one of said retractable
cord conductors, and a shield conductor connected to said
retractable cord shield layer; and further comprising an shield
substantially surrounding said spool inner chamber, said inner
chamber shield, spring, shield conductor and shield layer being
electrically connected to each other.
11. A retractable cord reel as in claim 3, wherein said inner cable
comprises a substantially flat ribbon cable.
12. A retractable cord reel as in claim 3, wherein said inner cable
is bonded to said spring.
13. A retractable cord reel as in claim 3, wherein said inner cable
comprises at least one conductive strip carried on said spring.
14. A retractable cord reel as in claim 3, wherein said spool
having a diameter of less than approximately 4 cm and having a
thickness of less than approximately 2 cm.
15. A retractable cord reel rotatable on an arbor, comprising: a) a
spool, rotatably mounted on the arbor, said spool having an annular
wall defining an outer trough and an inner chamber; b) a
retractable cord removably held in said outer trough, said cord
having a first end adjacent said annular wall; c) a spring coiled
in said spool inner chamber, one end of said spring attached to the
arbor and the other end of said spring attached to said spool, said
spring for rotating said spool in a cord retracting direction; and
d) an inner cable carried on said spring, one end of said inner
cable connected to said first end of said retractable cord.
16. A retractable cord reel as in claim 15, wherein said spring has
an insulating coating and said inner cable comprises at least one
conductive strip adhered to said spring coating.
17. A retractable cord reel, comprising: a) a housing having a
substantially cylindrical interior, a radial opening, and an axial
opening; b) an arbor in said housing; c) a spool mounted for
rotation on said arbor, said spool having an annular wall defining
an outer trough and an inner chamber, said annular wall having a
radial opening therein; d) an electromagnetic shield surrounding
said spool; e) a retractable cord removably wrapped in said trough,
said cord comprising a plurality of conductors, said conductors
having a first end adjacent said opening in said spool annular
wall, a shield layer over at least one of said conductors, one end
of said shield layer conductively connected to said spool shield,
and a reinforcing member, a first end of said reinforcing member
anchored to said spool; f) a spring in said spool inner chamber,
said spring having one end attached to said arbor and another end
attached to said spool; g) an inner cable in said spool inner
chamber helically wound with said spring, said inner cable having a
first end electrically connected to said first end of said
retractable cord conductors, and a second end extending axially out
of said reel at said arbor.
18. A miniature retractable cord reel for making a plural signal
connection between a source and a remote device, comprising: a) a
housing having a radial opening and an axial opening; b) an arbor
in said housing; c) a spool mounted for rotation on said arbor,
said spool having a diameter of less than approximately 4 cm and a
thickness of less than approximately 2 cm, said spool having an
annular wall defining an outer trough and an inner chamber, said
annular wall having a radial opening connecting said inner chamber
and said outer trough; d) a spring in said spool inner chamber, one
end of said spring attached to said arbor and a second end attached
to said spool; e) a substantially flat inner cable in said spool
inner chamber helically wound with said spring, said inner cable
having one end extending to said opening in said annular wall and a
second end exiting said housing axial opening, said second end
connected to one of said source or remote device, said inner cable
having plural signal conductors, and a shield conductor between
said plural signal conductors; f) an electromagnetic shield
surrounding at least said spool inner chamber and electrically
connected to said spring and said inner cable shield conductor; g)
a retractable cord removably wrapped in said spool trough, said
cord having a first end adjacent said opening in said spool annular
wall, and a second end extending through said radial opening in
said housing, said second end connected to the other of the source
or remote device, said retractable cord comprising plural signal
conductors, each of said cord conductors electrically connected to
a respective one of said inner cable conductors, a shield layer
surrounding at least one of said retractable cord conductors, a
first end of said cord shield layer electrically connected to said
inner cable shield conductor, and a fabric braid layer over said
conductors, a first end anchored to said spool and a second end
anchored to said other of the source or remote device.
19. A miniature retractable cord reel within a housing, comprising
a) a spool rotatably mounted in the housing, said spool having only
two compartments, namely an outer compartment and an inner
compartment; b) a retractable cord removably held in said outer
compartment of said spool; c) an inner cable helically wound in
said inner compartment of said spool, said inner cable connected to
said retractable cord; and d) means for rotating said spool in a
cord retracting direction.
20. A combination headset and retractable cord reel, comprising a)
a headset having a head band and at least one ear piece and a
speaker in said ear piece; b) a spool rotatably mounted to said
headset, said spool having an outer trough and an inner chamber; c)
a cord wound in the trough of said spool, one end of said cord
being retractable from said spool and said headset; d) a helical
spring in said inner chamber, said spring for rotating said spool
in a cord retracting direction; and e) an inner cable, at least a
portion of said inner cable helically wound with said spring in the
inner chamber of said spool, one end of said inner cable being
connected to the speaker in said headset and the other end of said
inner cable being connected to the other end of said retractable
cord.
Description
FIELD OF THE INVENTION OF THE INVENTION
[0001] The present invention relates to retractable cord reel
devices. In particular, the present invention relates to
retractable cord reel devices of a small size suitable for use with
hand held electronic devices such as cellular telephones and the
like.
BACKGROUND OF THE INVENTION
[0002] Retractable cord reel devices may be used to dispense and
automatically recall cords that connect one component of an
apparatus to another. The connection may be electronic, as in the
case of a small cellular telephone, for instance, where a
retractable cord reel may be used to connect a microphone and ear
piece or headphone to the base telephone unit.
[0003] Most cord reels comprise a rotating spool on which a
retractable cord is held. Some prior art devices provide rotating
electrical contacts between the spool and the spool housing or base
member. In electronic applications, particularly those involving
low current signals, moving contacts can cause static and other
undesirable signal disruptions. Further, contacts systems are not
very durable--the quality of the electrical contact deteriorating
with wear.
[0004] One solution to rotating contacts is to provide a second
cable, typically flat, within the cord reel that expands and
contracts as the retractable cord is retracted and returned. See,
for example, U.S. Pat. No. 5,094,396 to Paul C. Burke. However,
cord reels of this type may be too large for use with small
electronic devices, such as cellular telephones. Specifically, the
reel disclosed in the Burke '396 patent has multiple compartments
for the retractable cord, expandable cable, spring and ratchet. As
a result the housing is relatively large, and would not be suitable
for incorporation into a small electronic device such as a cell
phone.
[0005] Also, many prior art designs do not adequately address the
significant stress that is put on the moving parts of such small
reels. As a telephone ear piece is pulled by hand from a telephone,
a great deal of stress may result. Over repeated uses this stress
often results in failure of an electrical connection or mechanical
failures for the small gage cables (e.g., Litz wire) and other
parts used in prior art reel devices. Larger, more durable cables
are not practical because of the required small reel size, and
because of the need for a lightweight, flexible cord for use with
an earphone and/or microphone.
[0006] Also, many prior art cord reel devices suitable for use with
small applications do not provide for adequate shielding of
electrical signals from interference. This problem is particularly
acute for small telephones and the like using a microphone and
earphone of a very low voltage. Inadequate shielding results in
cross talk and other electronic noise. The small gage cables, small
cable reels, and small cable housings of many prior art designs
sacrifice adequate shielding for compact size.
[0007] There is therefore an unresolved need for a cord reel device
that is compatible with the particular challenges presented by use
with small electronic devices such as cellular phones and the
like.
OBJECTS OF THE INVENTION
[0008] It is an object of the invention to provide a cord reel
device of a compact design.
[0009] It is a further object of the invention to provide a durable
cord reel device having improved resistance to stress related
fatigue failures.
[0010] It is a still further object of the invention to provide a
cord reel device having effective shielding to electrical
interference.
SUMMARY OF THE INVENTION
[0011] The retractable cord reel of the present invention generally
comprises a housing or base plate supporting an arbor, a spool
rotatably mounted on the arbor, a retractable cord held on the
spool, and a device for rotating the spool to retract the cord. The
spool has an annular wall which defines an inner chamber and an
outer trough. The retractable cord is held within the spool outer
trough. A first end of the retractable cord is adjacent to the
annular wall, and the other end retractably extends outwardly from
the spool. The retraction device preferably comprises a spring that
is helically wound in the spool inner chamber. An inner cable is
also contained in the spool inner chamber, helically wound with the
spring. The inner cable has one end conductively connected to the
retractable cord, and a second end is stationary at the center of
the spool.
[0012] A preferred embodiment of the present invention is useful to
connect a cellular telephone base unit or source to a remote device
such as a ear piece and microphone. In this embodiment, the
telephone base unit provides a housing for the cord reel of the
invention. The arbor is mounted to the housing or on a base plate
contained within the housing. The spool is rotatably mounted on the
arbor. The housing includes a radial opening through which an end
of the retractable cord can pass. A ratchet mechanism may also be
held in the housing or base plate to selectively restrain rotation
of the spool. Although desirable, a ratchet is not strictly
required.
[0013] The retractable cord comprises a plurality of conductors, at
least one of the conductors, e.g., the mic conductor, is surrounded
by an electromagnetic shield. The plural conductors are in turn
covered by a reinforcing fabric layer. The reinforced fabric,
preferably nylon braid, is mechanically attached to the spool,
thereby providing a secure attachment that relieves the inner
conductors from mechanical stress. A small gage conductor, such as
Litz wire, can therefore be used without undue risk of failure.
Accordingly, the retractable cord has desirable qualities including
a small diameter, good flexibility, light weight, and good tensile
strength.
[0014] The spring is preferably connected at a first end to the
arbor, and at a second end to the spool, such as the annular wall
separating the inner chamber from the outer trough. The spring is
wound so that it builds and stores energy when the retractable cord
is retracted from the spool. Upon release of the cord, the spring
rotates the spool in a cord retracting direction.
[0015] An inner cable is helically wound with the spring in the
inner chamber of the preferred cord reel embodiment of the
invention. The preferred inner cable comprises one or more
conductors electrically connecting a source, such as the telephone
base unit, to the conductors of the retractable cord. The source is
directly connected to the retractable cord, thereby avoiding
intermittent disruption of signal that may result from moving
contacts as utilized in the prior art. Winding the inner cable with
the spring eliminates the need for a separate chamber or other
additional space. The inner cable may comprise a flat ribbon cable,
a strip conductor, individual conductors, or other configurations.
The inner cable may be attached to the spring, or it may be
separately wound with the spring. In any event, the conductors of
the inner cable are insulated from the spring.
[0016] A preferred inner cable comprises a plurality of conductors
carried on the spring having insulating layer(s) between the spring
and the conductors. The inner cable conductors preferably comprise
thin conductive strips, such as metal strips. The conductive strips
may be thin metal foils, or can be formed by painting or printing
conductive material onto a plastic or other insulating layer. The
sub-assembly of the conductors, insulating layers and spring may be
constructed in several ways. For example, plural, spaced apart,
conductive strips may be sandwiched between two layers of an
insulating material, such as mylar, and then adhered to the spring.
An alternative construction comprises, a layer of insulating
material adhered to the spring, plural spaced conductors adhered
over the insulating layer, and an insulating coating applied over
the top of the conductors. A third example comprises a layer of
insulating material adhered to the spring, plural spaced conductors
adhered over the insulating layer, and an insulating coating
applied to the bottom surface of the spring. Other ways of
insulating the conductors from the spring will be apparent to
persons skilled in the art.
[0017] The spool and/or the housing and base plate of the preferred
cord reel embodiment of the invention is shielded. The shield is
preferably a nickel plating or coating, providing an
electromagnetic/radio frequency interference ("EMI-RFI") shield. As
described above, the retractable cord likewise has a shielding
layer around at least one conductor. The inner cable, however, is
not required to have individual shielding as it is contained in the
inner chamber and thus shielded by the metal spring, and the
plating layers of the spool walls and/or the housing and base
plate.
[0018] The overall result of the space savings realized by the
compact retractable cord, the inner cable, and other compact
elements of the configuration of the spool of the invention allow
for a most advantageous compact spool size. The preferred spool has
a diameter of less than 4 cm (11/2 inch), and a thickness of less
than about 2 cm (3/4 inch), and most preferably less than 1 cm (3/8
inch).
[0019] The above brief description sets forth rather broadly the
more important features of the present disclosure so that the
detailed description that follows may be better understood, and so
that the present contributions to the art may be better
appreciated. There are, of course, additional features of the
disclosure that will be described hereinafter which will form the
subject matter of the claims appended hereto. In this respect,
before explaining the several embodiments of the disclosure in
detail, it is to be understood that the disclosure is not limited
in its application to the details of the construction and the
arrangements set forth in the following description or illustrated
in the drawings. The present invention is capable of other
embodiments and of being practiced and carried out in various ways,
as will be appreciated by those skilled in the art. Also, it is to
be understood that the phraseology and terminology employed herein
are for description and not limitation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is plan view of a cellular telephone and a
combination ear piece and microphone.
[0021] FIG. 2 is an exploded radial cross section through a
preferred embodiment of the invention.
[0022] FIG. 3 is an axial cross section of the spool of the
invention.
[0023] FIG. 4 is a cross section of one preferred retractable cord
of the invention.
[0024] FIG. 5 is a cross section of a portion of one preferred
spring and inner cable of the invention.
[0025] FIG. 6 is an elevational view of a headset and source
unit.
DETAILED DESCRIPTION
[0026] Turning now to the drawings, FIG. 1 shows a conventional
cellular telephone base unit A, ear piece B and microphone C. The
cellular telephone base unit A is merely one example of a source
unit. Other source units may include, for example, a tape recorder,
compact disc player, or radio. Likewise, the ear piece B and
microphone C are merely examples of remote devices. Other remote
devices may include, for example, stereo headphones. The cord reel
1 of the invention is contained within the base unit A. A
retractable cord 10 connects the source A to the remote devices B
and C. Alternatively, depending on the physical configuration of
the particular remote device, the cord reel could be carried by the
remote device, the retractable cable providing the connection to
the source. Indeed, the cord reel of the invention is sufficiently
small to fit within conventional stereo headsets. FIG. 6
illustrates a cord reel 1 of the invention mounted in headset D.
The headset has a head band E and at least one ear piece F. Ear
piece F houses a speaker G. Retractable cord 10 connects speaker G
to source H. Other applications for the cord reel of the invention
will be apparent to those skilled in the art. The specific
references herein to a cellular telephone and a headset are for
illustration, not limitation.
[0027] FIGS. 2 and 3 more specifically illustrate the cord reel 1
of the invention. The cord reel comprises a spool 2, retractable
cord 10, and inner cable 24. The spool has an annular wall 4
defining an inner chamber 6 and an outer trough 8. Trough 8 may
comprise a chamber, compartment, or other volume of space for
storing retractable cable 10. Approximately one meter of cord may
be held in trough 8. Trough 8 is shown as having side walls
perpendicular to annular wall 4, but it may have other
configurations. It is shown as being open at its radially outward
end, but trough 8 may be partially or fully enclosed by a housing
or the like. Opening 12 in annular wall 4 facilitates connection
between inner chamber 6 and outer trough 8. Spool 2, further
includes radial side walls 30 and 32. Alternatively, spool 2 may
comprise spokes or the like along the sides of inner chamber 6 in
lieu of side walls. A cover plate 33 is applied to cover the inner
chamber 6 after installation of spring 22 and inner cable 24. The
cover plate may be secured with a snap ring as illustrated, or
preferably, may be attached by deforming a few adjacent points of
the spool over the edges of the cover plate to permanently secure
the plate onto the spool.
[0028] The cord reel 1 may preferably include a housing 14 and base
plate 16. The housing and/or base plate may be part of the source
or remote device in or onto which the cord reel of the invention is
carried. An arbor 18 is attached to base plate 16. The arbor is a
spindle, hub, axle or other device onto which the spool 2 may be
rotatably mounted. Alternatively, the arbor may be attached to the
housing. The specific configuration of the housing, base plate and
arbor are not important, as long as the spool is rotatably
supported. Housing 14 has a radial opening 20 for passage of an end
of retractable cord 10, and an axial opening 23 for passage of
inner cord 24. Alternatively, inner cord 24 could exit the reel
through an axial slot in the base plate 16. Another option is that
the inner cord could terminate or exit at or near the central axis
of the reel. It should be understood that another cord or conductor
means may be used to connect the inner cable to the source. All of
these alternatives as well as other alternatives that will be
apparent to those skilled in the art are intended to be covered by
the appended claims.
[0029] The cord reel of the invention includes means for rotating
the spool 2 to retract cord 10. The cable retracting means may
include any known rotating devices, including springs, hand cranks,
motors and other means known in the art. A preferred spring 22 is
shown. Spring 22 is held in inner chamber 6 and helically coiled
about and attached to the arbor 18. Preferred spring 22 may be
fabricated by known techniques from spring steel, although other
metals or even polymeric materials may be used.
[0030] Inner cable 24 is helically coiled in inner chamber 6. In
the preferred embodiment, the inner cable 24 is helically wound
with spring 22. The inner cable may desirably be attached to the
spring. Alternatively, it may be wound with spring 22, but not
attached thereto. Inner cable 24 is conductively connected on one
end to retractable cable 10 through passage 12, with a second end
26 exiting spool 2 in an axial direction within or adjacent arbor
18. A second end 26 of the inner cable connects to the source, as
described above.
[0031] A conductive coating or plating for EMI-RFI shielding,
preferably nickel plating, may be optionally applied to the spool
and/or to the housing to shield the inner chamber 6. This shielding
layer is conductively connected to spring 22 through arbor 18 and
annular wall 4. Alternatively, the spool and/or housing and base
plate may be fabricated from metal or other conductive material,
thereby removing a need for a conductive coating or plating.
EMI-RFI shielding is desirable for some applications, such as low
voltage microphone signals. However other applications, such as the
headset of FIG. 6, do not require shielding. It is intended that
the invention as defined by the appended claims cover both shielded
and non-shielded retractable cord reels.
[0032] A ratchet may be optionally provided to selectively restrain
rotation of spool 2. The ratchet may comprise a pawl 28 pivotally
mounted to base plate 16 and spring 29. Spool 2 is provided with
notches 82. The spring 29 biases ratchet pawl 28 to engage notches
82 to selectively prevent rotation of spool 2 in a cord retracting
direction. A release lever (not shown) is provided to disengage
pawl 28 from notch 82 to allow the spring to rotate the spool in a
cable retracting direction. The ratchet herein is merely one
example of a suitable ratchet. Other ratchet mechanisms as are well
known in the art may be employed. Furthermore, the ratchet,
although desirable in most applications, is not strictly needed as
the invention is operative without any ratchet.
[0033] FIG. 4 is a cross section through retractable cord 10.
Retractable cord 10 is preferably comprised of plural, individually
insulated inner conductors 50. At least one of the conductors is
preferably shielded by a conductive layer 52. An outer reinforcing
layer 54 encloses the conductors. Shield layer 52 is preferably
comprises a copper braid. Reinforcing layer 54 is preferably
comprised of nylon braid for its excellent strength, relative small
size, and light weight. Fabric braid layer 54 is preferably
attached to the spool to limit stress/strain on the conductors, but
is some applications it may not be necessary to attach the
reinforcing layer to the spool. Attachment may be made in any
manner, such as by mechanically attaching the braid to spool 2 with
a pin 80, as shown in FIG. 3. Mechanical attachment may be made by
pulling back an end portion of preferred nylon braid layer 54,
heating it to fuse the braids together, and attaching the fused
braids to spool pin 80. Alternatively, the braid may be attached to
the spool with an adhesive. Alternatively a tail end of the fabric
braid may be inserted into a hole in the spool and knotted to
attach the braid layer to the spool. The opposite end of the braid
is mechanically anchored to the remote device C. Layer 54 will
carry the mechanical stress placed on cord 10 through use. Because
fabric braid layer 54 provides a great deal of tensile strength in
a relatively thin layer, cord 10 may thereby have a desirably small
overall diameter, good flexibility, and yet have sufficient tensile
strength to offer a prolonged service life.
[0034] FIG. 5 is a cross section of a layered portion of spring 22
with inner cable 24 in inner chamber 6. As indicated above, FIG. 5
illustrates an example of a preferred inner cable and spring, but
other configurations will be apparent and all such configurations
are intended to be covered within the scope of the invention, as
defined by the appended claims. A preferred inner cable 24
comprises a lower insulating layer 100 adjacent spring 22, a
plurality of intermediate conductors 102, and an overlying
insulating layer 104. Although insulating layer 104 is illustrated
as overlying conductors 102, it may alternately be underlying
spring 22, it being important only that the signal conductors be
insulated from spring 22. Individual conductors 102 may be attached
to insulating layers 100 and 104 by an adhesive, with underlying
layer 100 likewise affixed to spring 22 by an adhesive. Other means
of attachment may comprise heat bonding. Alternatively, conductive
strips may be painted or printed to the spring.
[0035] Alternatively, inner cable 24 may comprise a flat ribbon
cable adhered to or separate from the spring, or individually
insulated conductors affixed to or integral with spring 22. Other
alternatives will be apparent to those skilled in the art,
including, a spring comprised of a non-conducting polymer with an
elastic memory for spring like resiliency, with inner cable 24
comprising individual conductors electroplated or otherwise
deposited thereupon. A metal spring, however, is preferred as
polymer springs have been found to disadvantageously lose their
elastic memory at a much faster rate than the preferred metal
spring.
[0036] Inner cable 24 passes through the spool annular wall opening
12 and is conductively connected to retractable cord conductors 50.
Conductive connection may occur by splicing, by terminal
connection, or by other means as may be known in the art.
Alternatively, the conductors of retractable cord 10 may be unitary
with the conductors of inner cable 24. At the attachment point
adjacent annular wall opening 12, some slack is desirably provided
in the conductors to provide for strain relief, so that when
retractable cord 10 is pulled or otherwise stressed mechanical
loads are carried by fabric braid layer 54 and not by conductors
50. This helps to prevent failure of conductors 50, and allows for
a relatively small gage conductors 50 to be used so that
retractable cable 10 may desirably be small, lightweight, and
flexible.
[0037] It should be understood that although the retractable cord
and inner cable are shown and described as having ends and as being
spliced together, that retractable cord 10 and inner cable 24 may
be a unitary cord. Accordingly, the term "retractable cord" shall
mean the portion of the cable that is retractable, and the term
"inner cable" shall mean the portion of the cord in inner chamber
6. Indeed, in some applications it may be acceptable or even
desirable to have a flat, ribbon retractable cord, in which case,
the inner cable portion 24 and retractable cord portion 10 may be
portions of a continuous, unitary cable. It may also be feasible to
fabricate a unitary cord that includes a flat portion (desirable as
the inner cable) and a round portion (desirable at the retractable
cord). These and other variations as may be apparent to those
skilled in the art are intended to be covered by the appended
claims.
[0038] To further improve performance of the conductors of the
present invention with respect to freedom from electromagnetic
interference, the plural conductors 102 of preferred inner cable 24
of the invention comprises at least one shield conductor. In
reference to the cellular telephone example, two conductors are
required for the ear piece and one for the microphone. The inner
cable shown in FIG. 5 is comprised of four conductors. The left two
106 and 108 may used for the ear piece signals, and the right most
conductor 110 for the microphone. In between is a shield conductor
112. The low output microphone signal carried by conductor 110 is
thus shielded on the left by shield conductor 112, above and below
by spring 22 and at the right by cover plate 33 or by other
shielding carried by the spool or housing. Shield conductor 112 is
conductively connected to spring 22, spool shield layer 48, and
retractable cord shield 52 thereby providing a continuous, common
shield. For applications that do not require shielding, such as the
headset of FIG. 6, a shield conductor 112 is not required.
[0039] Although four individual conductors 102 are shown in FIG. 4,
the present invention may comprise any number of conductors as may
be required by a particular application. Also, as discussed infra,
other configurations of conductors 102, insulation layers 104 and
100, and spring 22 are within the scope of the present
invention.
[0040] By winding the inner cable 24 with spring 22, the present
invention solves several problems of the prior art. First, valuable
space is saved as the thin inner cable is contained in the same
chamber as spring 22; no separate chamber is required. If as is
preferred, the conductors 102 and insulation layers 100 and 104 are
supported by spring 22, they may be very thin and flexible without
risking high rates of failure. This provides additional space
savings. Further, the conductors 102 are in an environment of
excellent EMI-RFI shielding without requiring individual shielding.
Specifically, conductor 110 is shielded from EMI-RFI from above and
below by metallic spring 22, on one side by shield conductor 112
and on the other side by cover plate 33 and/or by spool wall nickel
plating layers. Additional space savings are thus realized as the
individual conductors 102 do not require individual shielding.
[0041] The advantages of the disclosed invention are thus attained
in an economical, practical, and facile manner. While preferred
embodiments and example configurations have been shown and
described, it is to be understood that various further
modifications and additional configurations will be apparent to
those skilled in the art. It is intended that the specific
embodiments and configurations herein disclosed are illustrative of
the preferred and best modes for practicing the invention, and
should not be interpreted as limitations on the scope of the
invention as defined by the appended claims.
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