I. BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This invention pertains to a jack assembly for use in the telecommunications or signal
transmission industries. More particularly, this invention pertains to an improved
switch assembly for such a jack.
2. Description of the Prior Art
[0002] Switching coax jack assemblies for use in the telecommunications or signal transmission
industries are well known. An example of such is shown in commonly assigned U.S. Patent
No. 4,749,968 to Burroughs dated June 7, 1988. The Burroughs patent teaches a switching
coax jack having a housing which contains two parallel spaced apart internal conductors.
Ports on the forward end of the jack permit a plug to be inserted within the jack
housing to make electrical contact with the conductors. The Burroughs patent teaches
two configurations where the forward end of the jack has either one or two forward
ports.
[0003] In Burroughs, a switch assembly is provided for normally connecting the internal
conductors but breaking the electrical connection upon insertion of a jack plug into
either of the forward ports. With best reference to Fig. 11 of U.S. Patent No. 4,749,968,
the jack includes a switch assembly 156 having a normal spring 164 in a generally
V-shaped configuration extending between the conductors 150,158. Upon insertion, a
jack plug 52 engages a termination spring 168 which deflects to urge a first portion
of a normal spring 164 away from conductor 150.
[0004] In switch designs, a risk of failure is presented by cyclic deformation of the normal
spring by repeated insertion of a jack plug into the jack assembly. Namely, the deformation
of the normal spring may result in breakage or plastic deformation of the normal spring.
[0005] The consequences of failure of the normal spring can best be appreciated by consideration
of the environment in which a jack assembly is used. The jack assembly is one of several
assemblies and other elements combined in a module (referred to as a "DSX module").
Examples of such modules are shown in U.S. Patent No. 4,815,104 (Figs. 1-6). In the
event of failure of a normal spring in a jack assembly, the entire module must be
replaced. This has severe economic consequences. The spring which fails is typically
inexpensive (for example, less than $1.00 U.S.). On the other hand, the module which
must be replaced upon failure of this spring can be quite expensive (typically greater
than $200.00 U.S.).
[0006] Even more significant than the adverse economic consequences resulting from spring
failure is the interruption in data or signal transmission resulting from such failure.
Modules incorporating switching coax jacks are commonly used in the telecommunications
industry for cross-connecting voice or data transmission lines. At high signal speed
transmission rates (known in the industry as DS-3 rates or greater), a single DSX
module may handle 672 voice conversations simultaneously. If a single normal spring
fails within the DSX module, the module fails and the many customers being serviced
by the module have their service interrupted.
[0007] Due to the significant economic and service interruption consequences attributable
to spring failure, the telecommunications industry has prudently placed a high premium
on reliability of spring contacts used in switching coax jacks. Accordingly, while
designs such as that shown in the Burroughs patent are commercially satisfactory (i.e.
the products are manufactured and designed to have a cycle life greater than any reasonably
anticipated cycling in the field and, therefore, they very rarely, if ever, fail),
the industry is continually looking for ways to increase the cycle life of such springs.
Cycle life means the number of times that a spring may be alternately deformed and
released before failure.
[0008] Customers continue to look for improved cycle life and may often make purchasing
decisions based on improved cycle life. This is true even though prior device cycle
life greatly exceeds anticipated cycling experienced in the field. Therefore, improvements
in cycle life are of significant economic consequence.
[0009] It is an object of the present invention to provide a switching coax jack having
an improved switch assembly to dramatically enhance the cycle life of springs within
the jack.
II. SUMMARY OF THE INVENTION
[0010] According to a preferred embodiment of the present invention, a switching coax jack
is provided having a jack housing containing first and second spaced apart conductors.
At least one port is formed in the jack housing and sized to receive a jack plug which
is inserted through the port. The plug engages the first conductor in electrical communication.
The jack housing contains a switch assembly for electrically connecting the first
and second conductors when a plug is absent from the port and for breaking the electrical
connection upon insertion of a plug. The switch assembly includes a normal spring
having a first portion biased into releasable electrical contact with the first conductor
and a second portion in electrical contact with the second conductor. Means are provided
for urging the first portion away from the first conductor in response to insertion
of a plug into the port. The switch assembly also includes a retaining mechanism for
retaining a central portion of the normal spring at a fixed location. The normal spring
is resiliently deformable in response to a force placed on the normal spring urging
it away from the first conductor. As the normal spring deforms, it assumes a predetermined
shape. The switch assembly further includes a support surface opposing the normal
spring as it is deformed. The support surface is shaped to be complementary to the
predetermined deformed shape of the normal spring.
III. BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Fig. 1 is a top plan view of a switching coax jack according to the present invention
with a portion of the jack housing removed to show the interior elements of the jack;
Fig. 2 is a top plan view of a prior art switch assembly;
Fig. 3 is a side elevation view, shown partially in section, of a switch assembly
according to the present invention;
Fig. 4 is a top plan view of a portion of the switch assembly of Fig. 3 showing a
normal spring in an undeflected position; and
Figs. 5-8 are top plan views of a normal spring surrounding a support post with the
spring shown in various states of compression from mild deflection (Fig. 5) through
fully deflected (Fig. 8).
IV. DESCRIPTION OF THE PREFERRED EMBODIMENT
[0012] Referring initially to Fig. 1, a switching coax jack 10 according to the present
invention is shown. The jack 10 includes a housing 12. Disposed within the interior
of housing 12 are a first electrical conductor 14 and a second electrical conductor
16. The forward end 13 of the housing 12 contains a first port 18 and a second port
20. Ports 18 and 20 are sized to receive a jack plug (not shown) of predetermined
dimensions. The ports 18 and 20 are disposed for a plug to electrically engage conductors
14,16 respectively, upon insertion into ports 18,20.
[0013] The embodiment shown in Fig. 1 has dual ports on the forward end 13. Alternatively,
only a single port (such as port 18) could be provided. As shown in the aforementioned
U.S. Patent No. 4,749,968, switching coax jacks having dual or single forward port
configurations are well known.
[0014] A switch assembly 80 is provided for electrically connecting the first conductor
14 with the second conductor 16 when a plug is absent from either of ports 18,20.
The switch assembly 80 is further selected such that the electrical connection is
broken upon insertion of a plug into either of ports 18,20.
[0015] It will be appreciated that a coax jack having an internal switch assembly is no
part of this invention per se. Such a jack is the subject of U.S. Patent No. 4,749,968.
The present invention is directed to an improvement in the jack assembly 80.
[0016] Before proceeding with a detailed description of jack assembly 80, a description
of a prior art jack assembly will be given to facilitate an understanding and appreciation
for the present invention. With best reference to Fig. 2, a prior art switch assembly
30 is shown. Switch assembly 30 includes a switch assembly housing 32, a normal spring
34 and a termination spring 36.
[0017] Normal spring 34 is generally V-shaped in configuration and includes a first portion
38 biased toward a first conductor (not shown) and a second portion 40 biased toward
a second conductor (not shown). An arcuate central portion 42 is disposed within an
arcuate slot 44 in switch housing 32 to retain the normal spring 34 in the switch
housing 32.
[0018] The termination spring 36 is generally U-shaped and includes a first arm 46 opposing
first portion 38 and a second arm 48 opposing second portion 40. Each of first and
second arms 46,48 are provided with dielectric contact pads 50,52 which are engaged
by a plug inserted within the jack to urge the arms 46,48 against first and second
portions 38,40 to thereby urge the first portions 38,40 against their natural bias
away from the internal conductors of the jack.
[0019] The switch housing 32 includes a support post 54 which has a semi-circular surface
56 which opposes central portion 42 of normal spring 34. At the ends of the semi-circular
portion 56, the support post 54 extends in flat surfaces 58 and 60 which are tangent
to the semi-circular portion 56.
[0020] We have determined that the structure thus described produces localized stress points
in the spring 34 as it is deformed by either of first or second arms 46,48. For example,
as portions 38,40 are deflected toward support post 54, localized stress occurs in
portions 38,40. The localized stress is positioned at locations A and B which are
located near or closely adjacent to the intersection of the flat surfaces 58,60 with
the semi-circular surface 56. The localized stress locations A,B are attributable
to the location of a fixed fulcrum point at these locations as the switch spring 34
is deflected. During very high repeated cycling of the switch springs about the fixed
fulcrum points A and B (i.e., test cycling beyond industry standards), the spring
can fail due to breakage or plastic deformation of the spring at the localized stress
points A and B.
[0021] Having described the prior art switch assembly 30, attention is now directed to Figs.
3-8 which show a switch assembly 80 according to the present invention.
[0022] Switch assembly 80 includes a housing 82 having an upper half 84 and a lower half
86 formed of dielectric material. For ease of illustration, only lower half 86 is
shown in Fig. 4 and only a normal spring and support post are shown in Figs. 5-8.
The housing 82 contains a generally V-shaped normal spring 88 and a generally U-shaped
termination spring 90.
[0023] Shown best in Figs. 4-8, normal spring 88 includes a first portion 92 and a second
portion 94 joined by an arcuate central portion 96. Arcuate central portion 96 is
retained in a fixed location in housing 82 by arcuate portion 96 being retained in
a generally semi-circular slot 98 formed in lower switch housing half 86 adjacent
a support post 114. First and second portions 92,94 terminate at contact ends 93,95.
[0024] Termination spring 90 has its central portion 91 received within a slot 100 formed
in housing half 86. A first arm 102 extends from portion 91 and terminates at a contact
end 103 opposing first portion 92. A second arm 104 extends from central portion 91
and terminates at a contact end 105 opposing second portion 94. The contacts 103,105
are first and second predetermined locations against which forces are applied on first
and second portions 92,94 to urge the normal spring 88 to deform as will be described.
[0025] First and second arms 102,104 are provided with contact pads 108,109 of dielectric
material. Contact pads 108,109 are engaged by a plug inserted within either of ports
18,20. In Fig. 4, normal spring 88 is shown in a relaxed position with no force being
applied at the contacts 103,105. When assembled into a completed switching jack 10,
as shown in Fig. 1, the spring 88 is partially deflected with arms 92,94 urged toward
one another as shown in Fig. 1. This deflection is necessary for the resilient bias
of the spring 88 to be utilized to insure a good electrical contact between contact
ends 93,95 and conductors 14,16.
[0026] Fig. 5 shows a portion of the view of Fig. 1 with the spring 88 partially deflected
against a support post 114 by an amount equal to the deflection of the spring between
conductors 14,16 (i.e., the amount of deflection shown in Fig. 1). Fig. 6 shows the
shape of spring 88 with portions 92,94 deflected toward post 114 in response to a
plug (not shown) partially inserted into ports 18,20. Fig. 7 shows the shape of the
spring 88 deflected further toward post 114 in response to further insertion of a
plug. Fig. 8 shows the shape of spring 88 with portions 92,94 fully deflected toward
post 114 in response to a plug being fully inserted into ports 18,20.
[0027] Through empirical observation, the shape of arms 92,94 when spring 88 is fully compressed
(as shown in Fig. 8) is determinable. Having predetermined the shape of the resiliently
deformed normal spring 88, the support surfaces or support ramps 110,112 of support
post 114 are shaped.
[0028] With best reference to Figs. 5-8, it is noted that support post 114 has a generally
semi-circular surface 116 opposing central portion 96. Support surfaces 110,112 are
generally parabolic and are shaped to be complementary to and conform with the predetermined
arcuate surface of arms 92,94 which have been fully deflected in response to urging
forces by contacts 103,105. The surfaces 110,112 are positioned to abut arms 92,94
when they are so deformed.
[0029] As a result of shaping surfaces 110,112 to be complementary to the deformed shape
of arms 92,94, the disadvantages associated with a fixed fulcrum point are eliminated.
Instead, the fulcrum point experienced by the bending or deformation of arms 92,94
is constantly moving along the length of arms 92,94. The length of surfaces 110,112
are selected so that they terminate at termination ends 111,113 spaced beyond the
contacts 103,105. Conveniently referred to as a "moving fulcrum" point, this phenomena
results in a distribution of stress along the length of arms 92,94 rather than having
the stress being localized as was the case in prior art switch assembly designs.
[0030] With reference to Figs. 5-8, the fulcrum point of portions 92,94 moves from locations
AA,AA′ to locations BB,BB′ as the portions 92,94 are deformed from Fig. 5 to Fig.
6. From Fig. 6 to Fig. 7, the fulcrums move from BB,BB′ to locations CC,CC′. Finally,
as the portions 92,94 are deformed to the position of Fig. 8, the fulcrums move from
location CC,CC′ to location DD,DD′.
[0031] By distributing the stress over the length of the arms 92,94, we project that the
cycle life of the normal spring 88 may be tripled (or better). This greatly enhances
the projected reliability of the jack 10 and the module of which it is a part.
[0032] In Figs. 5-8, surfaces 110, 112 are generally parabolic. However, this shape may
vary depending on the normal spring. The surfaces 110, 112 are selected to complement
the shape of any deflected normal spring. This shape is preferably selected from empirical
observations of a fully deflected normal spring so that a fulcrum or stress point
on the normal spring is constantly moving along the length of the spring as the spring
is being deformed.
[0033] In addition to greatly enhancing the life of the spring 88, the switch assembly 80
of the present invention includes means for incorporating electrical elements in a
more desirable manner.
[0034] As disclosed in the aforesaid U.S. Patent No. 4,749,968 termination springs such
as spring 90 are connected across a resistance to ground. The present invention incorporates
a novel technique for accomplishing that function.
[0035] Shown best in Fig. 3, the central portion 91 of the termination spring is generally
flat and, in the view of Fig. 3, is vertically oriented. A grounding clip 120 is shown
connected to the dielectric housing 82. The grounding clip 120 includes a cantilevered
grounding contact 122 (shown in Figs. 1 and 3). The grounding contact 122 has a contact
surface 124 which is generally perpendicular to the plane of portion 91. Disposed
between surface 124 and portion 91 is a ramp 126 formed on a surface of top housing
half 84. Preferably, ramp 126 is positioned at about 50° to the parting line 129 between
the upper and lower housing halves 84,86.
[0036] A chip resistor 128 of known surface mount technology is provided having contact
pads 130,132 disposed on edges of the chip resistor 128. Edge pad 130 opposes surface
124 and edge pad 132 opposes surface 91. The resilient cantilevered contact 122 urges
chip resistor 128 against portion 91 such that sound electrical contact is made between
surfaces 124,91 and pads 130, 132 respectively upon attachment of the grounding clip
120 to the housing 82.
[0037] Having described the present invention with reference to a preferred embodiment,
those skilled in the art will appreciate the many modifications and variations to
which the preferred embodiment may be made while retaining the concepts of the invention.
Accordingly, it is intended not to limit the scope of the protection of the present
application to the preferred embodiment but to include such modifications and equivalents.
1. A switching coax jack assembly comprising:
a jack housing;
first and second spaced apart electrical signal conducting means disposed within
said housing;
at least a first port formed in said jack housing and sized to receive a jack plug
to be inserted through said port and into said housing with said plug in electrical
communication with said first electrical signal conducting means;
a switch assembly for electrically connecting said first and second conducting
means when a plug is absent from said first port and for breaking electrical connection
between said first and second conducting means when the plug is inserted into said
first port;
said switch assembly including a normal spring of electrically conducted material
with said normal spring having a first portion biased into releasable electrical contact
with said first conducting means and a second portion in electrical contact with said
second conducting means;
said switch assembly further including urging means for urging said first portion
away from said first conducting means in response to an insertion of a plug into said
first port with said urging means applying an urging force on said first portion at
a first predetermined location;
said switch assembly including means for retaining said normal spring in said jack
housing with said normal spring having a portion held in a fixed location;
said normal spring first portion resiliently deformable from said fixed location
to said predetermined location in response to said urging force, said first portion
presenting a surface of predetermined shape as said first portion is deformed; and
said switch assembly including a support surface opposing said first portion as
said first portion is deformed, said support surface selected to be complimentary
to said predetermined shape.
2. A jack according to claim 1 wherein said support surface is positioned to abut said
predetermined shape when said first portion is deformed.
3. A jack according to claim 1 comprising at least a second port formed in said jack
housing and sized to receive a jack plug through said port and into said housing with
said plug in electrical communication with said second electrical signal conducting
means;
said normal springs second portion being resiliently biased into electrical contact
with said second conducting means;
said switch assembly urging means including means for urging said second portion
away from said second conducting means in response to an insertion of a plug into
said second port by applying an urging force on said second portion at a second predetermined
location;
said normal spring second portion being resiliently deformable from said fixed
location to said second predetermined location in response to said urging force, said
second portion presenting a surface of predetermined shape as said second portion
is deformed;
said switch assembly including a second support surface opposing said second portion
as said second portion is deformed, said second support surface selected to be complimentary
to said second predetermined shape.
4. A jack according to claim 3 wherein said second support surface is positioned to abut
said second portion.
5. A jack according to claim 1 wherein said first support surface is generally parabolic.
6. A jack according to claim 3 wherein said second support surface is generally parabolic.
7. A jack according to claim 1 wherein said first support surface extends at least to
said first predetermined location.
8. A jack according to claim 3 wherein said second support surface extends at least to
said second predetermined location.