Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to couplings ~or connecting
corrugated tuhes, and in particular, to couplinqs for
helically corrugated plastic drainage tubes.
Modern water drainage svstems comprise a network of
subsurface plastic tubes, some of which have s~aced openings
to collect and remove excess ground water, while others mav
be imperforate to convey the sollected water to a point of
disposal. Tubes for this purpose are commonly corrugated to
provide flexible yet sturdv conduits, and the corrugations
may be either circumferential or helical. Typically, the
grooves of helically corrugated tubes in standard 15 inch,
18 inch, and 24 inch sizes have a width of about one inch and
a pitch of about three inches. Plastic tubes of varying
lengths are combined to provide the arterial and branch
conduits of a complete drainage network. ~orrugated tube is
commercially available in long continuous lengths that are
generally cut into shorter segments for assemhly and
subsurface installation. The present invention relates to
couplings for joining the open ends of two aligned corrugated
tubes and especially for joining helically corrugated tubes.
Various coupling means have been proposed for
joining corrugated tubes; however, previously proposed
couplings include features which undesirably complicate and
increase the cost of their manufacture and application. ~ome
require relatively expensive and complex molding eauipment,
including separate molds for different sizes. Some include
integral studs or pawls or fasteners which require closed
matching molds, often with movable cores or side parts~ The
couplings produced are largely of limited applicabilitv, as
because thev fit only certain tube sizes, or fail to
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accommodate tolerance variations in tubes of the same nominal
size.
The present invention provides a tube coupling,
especially for helically corrugated tubes, which ls adapted to
be produced from thermoplastic sheet stock by simple
thermoformlng under pneumatic pressure, as in vacuum forming,
with minimal supplemental operations. The coupling thus formed
is easily applied, accommodates a workable range of tolerance
variations, and is secured in place with simple ties of a
readily available type. The couplings may be manufactured to
fit a single size of tubes, or may be made to fit large tubes
but formed and adapted to be cut at the time of installation to
fit smaller tubes. The present invention further provides
simple and inexpensive methods for forming such coupllngs.
In accordance with the present invention, there is
provided a sheet for forming a plurality of coupling bands for
connecting the ends of corrugated drain tube~ having external
grooves, the sheet comprising a plurality of parallel lines of
hollow lugs, the lugs being separated from each other by an
integral web of plastic material, each line of hollow lugs
including a plurality of spaced-apart columns of hollow lugs,
each column havlng ln sequence a flrst end lug formed to
include a flat end wall upstanding in substantially
perpendicular relation to the plastic web, a plurality of
intermediate lugs, and a second end lug formed to include a
flat end wall upstanding in substantially perpendicular
relatlon to the plastic web, adjacent spaced-apart columns in
each line belng arranged end to end to position the flat end
walls of the first end lug of one of the adjacent spaced-apart
columns and the second end lug of another of the adjacent
spaced-apart columns in confronting relation separated by a
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border area, the columns of each of the parallel lines of
hollow lugs being arranged to align sald border areas thereby
to define a plurality of parallel spaced-apart avenues in the
web, the web avenues being aligned in perpendicular relation to
the lines of hollow lugs, wherein each coupling band formed in
the sheet is defined by at least one transverse cut line
situated in one of the web avenues and a pair of laterally
spaced-apart sllt lines substantially normal to the at least
one transverse cut line, the hollow lugs being spaced
sufficiently along each of the parallel lines of lugs to permit
the coupling band when severed from the sheet to be wrapped
around the ends of the corrugated drain tubes and the parallel
lines of lugs being æpaced-apart so that the lugs thereof
engage in the external grooves of the two corrugated drain
tubes to permlt the ends of the tubes to be interconnected by a
coupllng band of the sheet, and wherein the flat end walls of
selected first and second end lugs have apertures formed
therein for the reception of coupllng band connectors so that
such end walls are ~olnable wlth coupllng band connectors to
hold a band severed from the sheet ln coupllng relatlon with
the tubes. The llnes of lugs ln the band are deslrably
oriented at an angle correspondlng to the pitch angle of the
tube corrugations so that the ends of the band will come
together in substantlal allgnment. Thus, for clrcumferentially
corrugated tubes, the llnes of lugs run stralght wlth the
length of the band, whlle for hellcally corrugated tubes the
llnes are at an angle correspondlng to the pitch angle of the
hellcal corrugations. By "pltch angle" ls meant the angle
between the tangent to the helix and a generator of the
cyllnder upon which the hellx lies. (Dictionary of Sclentlflc
and Technlcal Terms, McGrall-Hill Book Company, 197g).
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Preferably, the connectors are self-locking ties such
as the molded plastic ties readily available on the market.
The couplings are preferably and conveniently made by
thermoforming, for example, vacuum-forming, thermoplastic sheet
material to displace the hollow lugs from the sheet material in
a desired pattern. Large sheets may be formed with spaced
lines of spaced lugs to provide blanks which are then trimmed
and slit longitudinally to yield a number of coupling bands.
The length of the sheets may be such that when trimmed the
bands will be of a length to form couplings for a particular
size tube, and the angle o~ the longitudinal trim and slit cuts
may correspond to the pitch angle of that particular tube.
Alternatively, the length of the sheets may be such
as to yield bands to form couplings for a large size tube,
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for example, the standard 24-inch diameter tube, and the
pattern of lu~s may be such as to provide transverse cut
lines, with adjacent end border material and rows of end
lugs, so that the large couplings can be cut at such lines to
provide couplings for smaller tubes, such as the standard
18-inch and 15-inch diameter tubes. While in this case, a
trim and slit angle for the large size tube will not be
exactly corre~t for the smaller tubes, the result will onlv
be that the ends of the shorter couplings will not he exactly
aligned when the couplings are applied to the smaller tubes.
The misalignment is not substantial and will not affect the
coupling function or the convenience of its application.
It has been found convenient and practical to
thermoform different lengths of coupling bands on essentially
the same molding equipment. A vacuum-forming mold is
provided with lug-forming cavities in a pattern which
includes rows of end lugs and end borders at both ends, for
forming 24-inch couplings. ~he pattern also provides two
intermediate cut lines with rows of end lugs and end border
material ad~acent each cut line, with the cut lines located
to provide coupling bands suitable for 18-inch and 15-inch
couplings. Such mold can be used with long sheets to form
24-inch coupling bands or with shorter sheets to form 18-inch
and 15-inch couplings. The draw depths of the lugs are
relatively deep, and mold-assist elements such as draw plugs
for the hollow lugs may be used, in accordance with known
thermoforming practice.
Additional features and advantages of the invention
will become apparent to those skilled in the art upon
consideration of the following detailed description of a
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preferred embodiment shown in the accompanying drawings and
exempli~ying the best mode of carrying out the invention as
presently perceived. In such flrawings:
Fig. 1 is a perspective view of two aligned
helically corrugated tubes ~oined end-to-end by a couplinq in
accordance with the present invention, the coupling being
shown in partially wrapped position;
Fig. 2 is a side elevation of the tubes and
coupling of Fig. 1 with portions broken away and shown in
section;
Fig. 3 is a transverse section of the coupling
showing a self-locking connector extending through
confronting lug end walls to secure the coupling band about a
pair of aligned tubes;
Fig. 4 is a top plan view of a sheet of
thermoplastic material having spaced lines of spaced lugs
formed therein, showing trim and slit lines at an angle to
the length of the sheet and the lines of lugs;
Fig. S is a longitudinal section of the formed
sheet, taken on the line 5-5 of Fig. 4; and
Figs. 6 and 7 are perspective views showing
alternative forms of end lugs and apertures therein.
As shown in Fig. 1, a coupling 10 is engage~ about
a pair of coaxially aligned helically corrugated tubes 14 to
join the tubes 14 end-to-end. The tubes are formed with an
external helical groove 12. The coupling 10 comprises a band
16 including a plurality of spaced lines 17 of generallY
uniformly spaced intermediate lugs 18 and end lugs 20 to
engage in the corrugation grooves 12 of the tubes 14. The
end lugs 20 are adjacent the end of the band 16 ana
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spaced from the end edges 22 sufficiently to leave end
flanges or borders 23. The end flanges or borders 23 are
adapted to overlap when the coupling is in place about the
tubes, and are of sufficient width to overlap a variable
amount so as to accommodate tolerance variations in the size
of the tubes 14. The intermediate lugs 18 are desirablv
frustums of regular four-sided pyramids, and longitudinally
spaced apart by flat sections 19 to provide flexibility of
the sheet. The end lugs 20 are similar but shaped with end
walls 21 more nearly perpendicular to the sheet so as to
stand generally radially of the tubes and in generallv
parallel spaced relation when the coupling band is wrapped
about the tube.
Such end walls are punched or otherwise formed with
apertures 30 which come into general alignment when the band
is in place. The coupling band is secured about the ends of
the tubes 14 by connectors 24 which are passed through the
aligned aperture 30 when the band has been wrapped about the
tube ends. Desirably, such connectors 24 are molded plastic
ties formed at one end with integral self-locking buckles,
which are readily available on the market. As shown in
Fig. 3, these can be applied with the buckles positioned
within one of the hollow end lugs. The extra strap length
can then be cut off so that the ties do not protrude to
obstruct application of a ilter sleeve as in Patent No,
4,104,774.
Coupling bands 16 in accordance with the present
invention are desirably made by first preparing a blank 26 as
shown in Figs. 4 and 5. An extruded sheet of thermoplastic
material is thermoformed, as by vacuum-forming, to form the
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blank 26 having a series of laterally spaced lines 17 of
longitudinally spaced hollow lugs, including intermediate or
body lugs 18 and end lll~s 20. The intermediate lugs 18 are
of generally frusto-pyramidal shape adapted to fit into the
grooves 12 of the drain tubes 14 with which the couplings are
to he used. The lugs are formed hy displacement from the
sheet of thermoplastic material in a conventional
thermoforming procedure such as vacuum forming. The lugs
desirably involve a relatively deep draw, and the
thermoforming may be assisted by the use of conventional
plug-assist elements to move material into the mold cavities
before applying the vacuum to form such material to its
desired shape. The lugs in each line are spaced sufficiently
to allow the resulting coupling hands to bend freely about
the drain tubes to which the couplings are applied.
A transverse row of end lugs 20 are formed adjacent
each end of the blank in spaced relation from the end trim
line 22 at which the blank will be trimmed to form its end
edges 22, so as to leave an end flange or border 23 between
such row of end lugs 20 and such end edge 22. The end walls
21 of the end lugs 20 stand at a greater angle tban the side
walls of the intermediate lugs 18, desirably clase to a
90 angle to the web of the blank 26, so that when the
coupling bands are applied to the drainage tubes, such walls
will stand in a generally parallel confronting relation, as
shown in Fig. 3.
When the blank 26 has been formed with the lugs, it
is removed from the mold and trimmed at the end trim lines
22, parallel to the end rows of end lugs 20 and spaced
therefrom to provide end borders 23 of predetermined width.
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The blank is then also trimmed at its edges along side trim
lines 28 and slit on slit lines 29 to form a pluralitv of
coupling bands 16. These side trim lines 28 and the slit
lines 29 are parallel, so as to form bands of uniform width.
For helically corrugated tubes, such lines are desirablv at a
small angle to the lines 17 of lugs, corresponding to the
pitch angle of the tubes on which the coupling bands are to
be used.
Preferably, large-size coupling bands are also
formed with intermediate transverse cut lines 32 at which the
large coupling band can be cut to provide couplinq bands to
fit smaller tubes. Thus as shown in Figs. ~ and 5, the blank
26 is shown with a transverse cut line 32 at which long bands
can be cut in the field to a 59-inch length to fit 15-inch
drainage tube, and a transverse cut line 33 at which cuts can
be made to provide bands of fi8-inch length to fit 18-inch
drainage tubes. At each cut line 32 and 33, the blank is
formed with flange or border portions 23 ad~acent the cut
line, and the adjacent row of lugs to the left of the cut
line are formed as end lugs 20 with more nearly perpendicular
end walls 21 80 that when the shorter bands are used on
smaller pipes, such end walls 21 will come together in
confronting, substantially parallel spaced relation as shown
in Fig. 3. As shown, the lugs 20' to the right of the cut
lin~s are also formed as ena lugs and spaced from the cut
lines 80 that the shorter pieces cut off in the field can
also be used on smaller tubes. Thus two such pieces cut off
full 88-inch length bands to form 59-inch bands for 15-inch
tubes will have lengths of 29 inches and can be combined to
form another band for a 15-inch tube.
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When hlanks 26 are formed to provide large-size
coupling bands and to be cut to provide s~rter coupling
bands for smaller tubes, the angle at which the side trim
lines 28 and slit lines 29 are cut may be selected to
correspond to the pitch angle of an intermediate-size
drainage tube. Thus as shown in Fig. 4, the trim line 28 and
parallel slit line 29 are at an angle of approximately 1 57'
corresponding to the pitch angle of standard 18-inch drainage
tubes. While this will result in some deviation from
alignment when full-length bands from the same blank are
applied to 24-inch tubes and shorter bands are applied to
15-inch tubes, the misalignment of the band ends is not
substantial and does not interfere with the function of the
coupling. Instead of orming shorter-length bands by
providing cut lines in longer-length bands, blanks 26 can be
made of a length to provide bands 16 to fit snecific sizes of
tubes. In that case, the bias angle of the side trim lines
28 and slit lines 29 can be made to correspond closely to the
helix angle of the particular tube on which the bands are to
be used. In such case, also, the pattern of lugs may be
originally molded on lines at an angle to the longitudinal
dimension of the blank, rather than being molded on lines
parallel to such dimensions as contemplated in Fig. 4. These
same procedures can be used to produce coupling bands for
circumferentially corrugated tubes, in which case the blank
is trimmed on lines parallel to the lines of lugs rather than
at a bias angle thereto.
~ he apertures 30 in the end walls 21 of the end
lugs 20 can be formed in various ways. As shown in Fig. 6,
the end walls 21 of end lugs 20 are punched or drilled to
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form round apertures 30. This procedure requires that the
apertures be formed as supplemental steps, after the blank
has been trimmed to its final lenqth. Alternatively,
elongated apertures 31 as shown in Fig. 7 may be formed by
saw cuts through the end walls 22 along each row of end walls
20 of a blank 26, and such cuts can be made either before or
after the blank 26 has been trimmed or slit or cut to length.
For example, a small circular saw can be passed along the cut
line 32 of the blank shown in Fig. 4 to cut elongated
apertures in the form of saw kerfs ~1 in the end walls 21 of
the end lugs 20 adjacent that cut line.
The present invention provides drain tube couplings
of inexpensive construction adapted to securely connect the
aligned ends of two corrugated drain tubes and to accommodate
tolerance variations in the sizes of such tubes. The
coupling bands can be formed by simple thermoforming
processes, such as vacuum-forming, and are not molded with
integral connectors which require manufacture in matched
molds. The lugs of the coupling band are so formed and
arranged that they provide confronting parallel spaced walls
at the adjoining ends of the wrapped band, which walls can be
easily provided with aligned apertures for the reception of
separate connectors such as commercially availahle
self-locking ties. These can be pulled tight to draw the
coupling band close about the tube ends with the band ends
overlapping to whatever extent is required to closely fit the
aligned tubes and form a secure ~oint between them.
The invention has been described in detail with
reference to a preferred embodiment exemplifYinq the best
mode of carrying out the invention as presently perceived,
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but it will be understood that variations and modifications
of such embodiment mav be made within the scope of the
invention as defined in the followin~ claims.
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