Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CCO 2 060
~OUPLIN~ FOR CORRU~ATBD TV~IN~
BACKGROUND OF THE INVENTION
The sub~ect lnvention 1~ directed toward the art of
tube couplings and, more partloularly, to a molded, pla~tlc
coupllng especlally suited for ~olning corrugated plasti¢
tubing.
The lnventlon wlll be described with reference to use
of the coupling on a particular type of fittlngs however, as
will become apparent, the coupling could be used on a varlety
of types of fittings or formed as an lntegral part of various
structures such as switch boxes, ~unction boxes and the like.
Many dlfferent snap-in or push-in type couplings have
been proposed for use with corrugated plastlc pipe and
tubing. One typical prior art coupling comprises an open
ended cylindrical coupling body with the interior of the body
sized to closely receive the exterior of the corrugated
tubing. Inwardly extending tabs or fingers are carried
within the body and lnclude end portlons which enter the
recesses between adjacent corrugations to latch into the
tubing and prevent its withdrawal. Couplings employing this
general arrangement are illustrated, for example, in U.S.
patents 4,441,745: 4,575,133 and, 4,711,472.
one of the problems with these prior couplings has
been that their design, primarily their geometry, results in
inherent strength lim~tations. That is, their ability to
reaist tublng wlthdrawal is somewhat more limited than would
be desirable. Applicants' have found that these limitations
result because the latching tabs or fingers have their polnt
of primary pivoting or flexing in the cylindrical wall of the
coupling body substantially at the outer diameter or surface
of the tubing. As a aonsequence, the pivot point and the
point at ~hich load is applied to the finger a~e nearly in
alignment in the direction of the tubing pull-out force.
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202~ 7~4
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This result~ in a 60mewhat unstable latching condition. In
fact, it is similar to an over center mechanism at or near
its center position where a small lateral movement causes ~t
to go over center. In the prior art type coupling a similar
but undesirable result can take place when the end of the
finger or the slde of the engaged corrugation deform~
slightly.
BRIEF STAT~MENT OF ~HE INVENTION
The ~ub~ect inventlon overcomes the noted problems and
provides a coupling structure wherein the latch fingers are
oriented and shaped to produce an improved latching geo~etry
and increased 6trength. More particularly, the invention
provides a connector fitting for ~oining to the end of non-
metallic conduit of circular cross section having alternating
circumferential protrusions and recesses. The connector
fitting of the invention comprises a sleeve formed from
pla~tlc and encloslng an inter10r chamber defined by a
continuous peripheral s~de wall of substantially uniform
thickness. The sleeve has an axial~y opened outer end sized
for receiving the end of the non-metalllc conduit. A stop
surface is located in the sleeve axially inwardly of the open
end for limiting the inward extent of movement of the end of
the condult. The peripheral ~ide wall includes a first pair
of wall sections located in dlametrically opposed
relationship extending axially inward of the interior chamber
from the open end. The first pair of wall Bection8 i8 spaced
and conflgured to closely engage and guide the end of the
conduit as it enters;the chamber. A ~econd pair of wall~
~eotlons compl~tes the peripheral slde wall at least in the
area ad~acent the open end. The second pair of wall sections
1B located in diametrically oppo6ed relationship
clrcumf~rentially lntermediate the f1rst palr of wall
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gections. The first and second wall ~eations are integrally
connected by transition sectlon~ and the second pair is
located such that they are spaced radially outwardly a
substantial distance from the exterlor of the end of the
conduit when it i8 in the chamber. ~ resilient latch tab
having a thickness substantially equal to the thickness of
the wall sections is carried by each of the second wall
sections and is formed integrally therewith. The tabs have
base portlon~ arranged for flexure at the radius of the
second wall sections and the body of each of the tabs is
inclined to extend axially and radially into the chamber and
terminate in a free end located to extend into and latch in
a recess on the end of a conduit received in the chamber.
Preferably, and in accordance wlth a more specific
aspect of the invention the ends of the latch tabs are
located in a plane which extends generally perpendicular to
the axis of the interior chamber. Additionally, they have
thelr free end radially inward of the flrst palr of wall
sections.
Because of the arrangement of the second wall sections
and the fact that the latch tab~ extend inwardly therefrom,
the latch tabs pivot about a point or axis which is located
a substantial distance radially outward from the tubing.
This provides a much more positive gripping relationship and
assures that the tubing wil~ be held tightly and that
attempted movement will produce an increasing gripping
reaction between the latch tabs and the tubing.
~ecause of the defined relationship between the wall
sections, together with their uniform thicXness, the coupling
is extremely rigid and is not weakened or structurally
compromised by the positioning of the tab~
Accordingly, the primary ob~ect of the invention is
the provision of a molded plastic connector for corrugated
tubing wherein an extremely advantageous relationship between
the locklng tabs and the corrugated tubing results because
of the exterior design and mounting of the tabs.
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Yet another ob~ect of the invention i~ the provision
of a molded pla~tlc coupling of the type described wherein
the coupling ha~ a somewhat elliptical body shape to most
desirably po~it~on the tabs relative to the tubing.
A still further ob~ect is the provision of a
corrugated tube coup~lng design where~n attempted withdrawal
of the tublng results ln an lncreased locking force belng
generated by the locking tabs.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other ob~ects and advantage~ will become
apparent from the following description when read in
con~unction with the accompanying drawings wherein:
FIGURE l is a pictorial view of a fitting
lncorporating a corrugated tube coupllng formed in accordance
with the sub~ect invention:
FIGURE 2 i~ an end vlew of the right hand end of the :
fitting shown in FIGURE l;
FIGURE 3 i8 a cros~-sectional view taken on line 3
3 of FIGURE 2;
FIGURE 4 is a view slmilar to FIGURE 3 but showing a
corrugated tubing end in assembled position in the fitting:
FIGURE 5 iB a greatly enlarged view of the circled
area of FIGURE 4: and,
FIGU~E 6 is a view taken on line 6-6 of FIGURE 2.
~5 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referrlng more particularly to the drawing~ where the
showings àre for thei purpooe of iIlustrating a preferred
embodlment of the invention only, and not for the purpose of
limiting ~ame, FIGURES I through 3 show the overall
arrangement of a molded, one-piece plastic fitting 10
designed to ~oin corrugated plastlc tubing to a panel member
or ~unction box assembly. The fitting 10 is merely one form : :~
of fitting in which the coupllng of the sub~ect invention
could be utllized. That l~, the improved coupling portion
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of the fitting 10 could be formed on other types of fittings
or integrally with ewitch boxe~, junction boxes or the like.
In thi~ embodiment, fitting 10 comprises a first cylindrlcal
end portlon 12 which is provided wlth exterlor threads 14
that allow the end portion 12 to extend through a preformed
openlng ln a panel or ~unctlon box wall and be connected
thereto through the use of a sultable nut received on the
threads 14. A panel 16 and a sultable connectlng nut lB are
shown in phantom in FIGURE 3.
lo The rlght hand end of fittlng lo ~as vlewed ln FIGURES
1 and 2) defines the improved coupling portion and comprises
a somewhat enlarged sleeve sectlon 20 which is forme~
integrally wlth section 12 and connects therewith by a radial
wall portlon 22. As best seen in FIGURE 3, sleeve sectlon
20 define~ an interior chamber 24 which ha~ lts rlght hand
end open to define a mouth or entrance for receipt of
corrugated tubing in a manner ~ubsequently to be described.
The left hand end of chamber 24 ~oins to a central passage-
way 26 formed through section 12.
The sleeve portion 20 is deflned by a first pair of
radially oppo~ed wall section~ 28 which each have a ~ ~",
circumferential extent of approximately 90 degrees as best
seen in FIGURE 2. The wall sections 28 preferably have a
thickness T which is generally uniform throughout their
circumferential extent. The interior wall surface 28A of the
wall sections 28 i9 located at a radial distance R~ from the
axis of the coupling. This radius Rl is only slightly larger
than the maximum exterior radius on the tubing which is to
be ~oined in the coupling. This allows the lnterior surfaces
28A to act as guide surfaces for closely engaging about the
exterior of the corrugated tubing to guide and hold it
properly located in the chamber 24. -~
The sleeve 20 further includes a second pair of
opposea wall sections 30 which are located circumferentially
lntermediate the wall sections 28 on dlametrically opposed
sides of the chamber 24. Wall sections 30 hava a thickness
~ ~ 2~7~
T2 which iB substantially equally to thickness r,. It is
important to note that wall sections 30 are dlsplaced
radially outward from the location of wall sectlons 28 and
are ~olned to wall ~ectlon~ 28 by tran~ltlon sectlon~ 32.
According to the invention, the wall sections 30 are
preferably displaced radlally outward relatlve to the wall
sectlons 28 by a distance whlch is approxlmately equal to
wall thickness Tl. As best lllustrated ln FIGURE 2, the
radlus R2 is approximately at least equal to the 6um of
radlus R~ plu~ Tl. The lmportance of this relatlonshlp will
subsequently become apparent.
As best shown in FIGURES 3 and 4, the axlally
lnnermost end of the chamber 24 i8 of uniform dlameter
throughout lts circumferential extent and is located at
radlus Rl. Thus, the lnnermost end of the tubing 18 gulded
throughout its circumferential extent and 18 prevented from
havlng any appreclable radial freedom of movement.
FIGURE 4 shows the fitting 10 wlth a section of tubing
36 positloned therein. As lllustrated, the lnner end of the
tublng engages with the radlal wall 22 to provide an axial
llmlt to movement and positioning.
The tubing 36 18 maintained locked in the assembled
posltlon lllustrated ln FIGURE 4 by a palr of relatively
rigid latch tab members 40 which axe carried from the opposed
wall 8ections 30 as lllustrated. A8 best shown in FIGURE 6,
each of the wall sections 40 is centrally po~itloned from the
assoclated wall sectlon 30 and extends radially and axially
into the chamber 24. A generally C-shaped opening 42 ls
formed aboùt each o`f the latch tabs 40 so that the tabs can
move freely ln a radial direction. The latch tabs 40 extend
axially and radially lnward and termlnate ln a free end
portion 42 which has an end face 44 (see FIGURE 5) which
preferably lles ln a plane perpendicular to the longitudinal
axis of flttlng 10. Preferably, each of the latch fingers
40 has a thlckness which is as greàt or greater than the
thlckness Tl of the wall sectlon 28. Addltionally, the inner
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surface of each latch tab 40 i~ preferably inclined at a
first angle A which is in the range of 15 to 25 degrees and
a second angle B which is ln the range of 45 to 50 degree~,
as best seen in FIGURE 3. The lncline is designed so that
as the corrugated tublng is moved lnto the chamber 24 the
latch tabs 40 are cammed radially outward until the tublng
3 6 i8 in the located position shown in FIGURE 4. At this
time the inner dlstal end~ of the latch tabs 40 enter between
ad~acent corrugation~ to lock th~ tublng in the position
lo shown. In order to assure the proper pivoting of the tabs
and allow manual in~ertion of the tubing 36 into the fitting
a relief groove or the like 46 can be formed along the base
of each latch tab 40. This results in a thinning of the
material in this area so that greater flexiblllty of the
pivot area of associatea latch tab is provided.
As can readily be seen from FIGURE 5 the sub~ect
arrangement assures that the pivot point "P" for the latch
tabs 40 ls located radially outward a substantial di6tance
relative to the point of applicatlon of forces to the latch
tab by the tubing. This produces a distinct latching effect
for each latch tab and assures a radially inward directed
movement of the latch tab to more tightly grip the tubing if
an attempt is made to withdrawal the tubing from the fitting.
In addition, the shape of the latch tab resulting from the
arrangement of the lnternal surface~ provides a greatly
strengthened latch tab in the area of greatest force
appllcation. This provides a very rigid tab body and ~ ~ ~
prevents collapse of the body during force application. ` ~ ~ ;
The invention has~ been de~cribed in great detail
sufficient to enable one of ordinary skill in the art to make
and U8Q the same. obviously, modifications and alterations
of preferred embodiment wlll occur to others upon the reading
and understanding of the sub~ects ~pecifications and it is
our intention to include all such modifications and ~ -
alteratlons as part of our invention insofar as they come
within the scope of the appended claims. - ,~
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