Coupling for corrugated conduit

An improved coupling for a corrugated conduit includes a main tubular body with a sleeve defining a conduit receiving bore terminating at its inner end in an annular shoulder projecting radially inwardly of the tubular body. A nipple clamps the end portion of the conduit and is inserted together therewith into the conduit receiving bore where it is pressed forwardly by rotating a nut threaded on the sleeve for forcing the end of the conduit into pressing contact with the shoulder. The nipple is externally shaped to have a polygonal configuration so as to be slidably but unrotatably inserted in the correspondingly shaped conduit receiving bore, preventing the conduit from being twisted during the securing operation of rotating the nut about the sleeve.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention is directed to a coupling for a corrugated conduit, 
and more particularly to such a coupling utilized as an attachment of an 
end of the corrugated flexible conduit to a device or fitting with which 
the fluid medium conveyed by the conduit is utilized. 
2. Description of the Prior Art 
Such couplings for the corrugated conduit or hose have been extensively 
utilized in gas conveying system as well as in other fluid conveying 
systems. A typical prior coupling for the corrugated conduit is shown in 
Japanese unexamined Patent Publication (KOKAI) No. 60-73193 in which the 
end of a corrugated conduit is clamped by a nipple and is inserted 
together therewith into a sleeve on one side of a main tubular body. A nut 
is threaded on the sleeve to have a collar at its end in abutting 
engagement with the rear end of the nipple for pressing the nipple 
together with the end of the conduit forwardly into the sleeve, forcing 
the latter into sealing engagement with an annular shoulder projecting 
radially inwardly of the tubular body. In this prior coupling, however, 
the nipple is shaped to have a circular external configuration relatively 
freely rotatable within the sleeve so that it tends to be rotated by the 
frictional force developed at the abutment between the nut and the nipple 
as the nut is rotated on the sleeve in advancing the nipple and the end of 
the conduit into the sleeve, thereby subjecting the conduit to twisting or 
kinking forces which would damage the conduit or render the subsequent 
procedures to be rather inconvenient. 
SUMMARY OF THE INVENTION 
The present invention has been accomplished in view of the above 
shortcoming and provides an improved coupling for a corrugated conduit. 
The coupling in accordance with the present invention comprises a main 
tubular body having a sleeve at its one end defining therein a conduit 
receiving bore terminating at its inner end in an annular shoulder 
projecting radially inwardly of the main tubular body midway between the 
ends of the axial bore. A nipple is provided for clamping an end portion 
of the conduit with corrugations of the conduit left projecting beyond the 
forward end of the nipple and is inserted into the conduit receiving bore 
of the sleeve together with the end portion of the conduit. A series of 
serrations are formed interiorly of the nipple to be in registering 
engagement with the corrugations at the end portion of the conduit for 
firmly gripping the conduit. The nipple has its rear end abutted against a 
collar at one end of a nut threadedly fitting about the sleeve to be 
thereby pressed forwardly into the sleeve in order to force the end of the 
conduit into pressing engagement with the annular shoulder as the nut 
being rotated. The characterizing feature of the present invention resides 
in that the nipple is shaped to have a polygonal exterior configuration to 
be fitted in a correspondingly shaped section of the conduit receiving 
bore so as to be slidably but unrotatably inserted in the sleeve. With 
this result, the nipple and the end portion of the conduit can be pressed 
into the sleeve without being rotated, obviating the occurrence of 
twisting or kinking of the conduit while ensuring effective pressing 
contact between the end of the conduit and the shoulder. 
Accordingly, it is a primary object of the present invention to provide a 
coupling for a corrugated conduit in which the conduit is free from being 
subjected to twisting or kinking forces at the time of rotating the nut 
for securing the conduit to the sleeve. 
In a preferred embodiment, the nipple is prepared in the form of a split 
member composed of a pair of semicylindrical halves connected by an 
integral thin-walled hinge portion to be easily separable therefrom. The 
nipple is in use to be separated into the two halves which are then placed 
about the end portion of the conduit with the serrations being in 
registering engagement with the corrugations of the conduit so as to be 
inserted into the sleeve as clamping the end portion of the conduit. With 
the use of this split nipple, the corrugations at the end portion of the 
conduit can be readily brought into registering engagement with the 
serrations of the nipple so that the end portion of the conduit can be 
securely and firmly gripped by the nipple. 
It is therefore another object of the present invention to provide a 
coupling for a corrugated conduit in which the end portion of the conduit 
can be easily and firmly clamped by the separable nipple. 
Formed at the juncture of the shoulder and the conduit receiving bore of 
the sleeve is an annular groove for receiving therein a sealing ring which 
is to be disposed around the end of the conduit pipe when it is forced 
into pressing contact with the shoulder. The sealing ring has its side in 
abutting relation with the forward end of the nipple so that it is 
compressed axially by the nipple inserted in the sleeve to elastically 
expand radially for establishing sealing contacts between the sealing ring 
and the wall of the groove and between the sealing ring and the end of the 
conduit being pressed against the shoulder. In this sense, the nipple 
pressed forwardly into the sleeve by the nut can serve not only to guide 
the end of the conduit into pressing engagement with the shoulder but also 
to effectively deform the sealing ring for the purpose of providing an 
increased seal between the conduit and the sleeve. 
It is therefore a further object of the present invention to provide a 
coupling for a corrugated conduit capable of increasing the effectiveness 
of the seal between the conduit and the sleeve. 
These and other objects and advantages of the present invention will be 
more apparent from the following detailed description of the embodiment 
when taken in conjunction with the attached drawings.

DETAILED DESCRIPTION OF THE EMBODIMENT 
Referring now to FIG. 1, there is shown a coupling for a corrugated conduit 
1 embodying the present invention. The coupling comprises a main tubular 
body 10 having an axial bore 11 and having on its one end portion an 
externally threaded sleeve 12. The other end portion of the main tubular 
body 10 defines a head portion including a hexagonally shaped flange 13 
and a male member 14 being in the form of an externally threaded tapered 
barrel and projecting outwardly from the flange 13 for connection with any 
suitable devices or fittings. The sleeve 12 defines therein a conduit 
receiving bore 15 of hexagonal configuration which has a diameter larger 
than the rest of the axial bore 11 and terminate at its inner end in an 
annular shoulder 16 projecting radially inwardly midway between the ends 
of the axial bore 11. The corrugated conduit 1 is made of metallic 
material to include a series of uniform corrugations having relatively 
rounded crests alternated by relatively rounded roots, as best shown in a 
longitudinal cross-sectional view of FIG. 2, and is relatively thin-walled 
to be flexible. 
For connection of the corrugated conduit 1 to the main tubular body 10, the 
conduit 1 is inserted as being clamped by a nipple 20 into the conduit 
receiving bore 15 of the sleeve 12 together therewith and is secured by 
rotating a nut 30 threadedly engaged on the sleeve 12. The nipple 20 is 
shaped to have a hexagonal exterior configuration to be slidable but 
unrotatably inserted into the hexagonally shaped conduit receiving bore 15 
of the sleeve 12. Formed internally of the nipple 20 are a series of 
serrations 21 which are in intimate mating or registering engagement with 
the corrugations of the conduit 1 to firmly grip the latter. As shown in 
FIG. 4, the nipple 20 is prepared in the form of a split tube composed of 
a pair of semicylindrical halves 22 connected by a thin-walled hinge 
portion 23 diametrically opposed to a slit 24 to be easily separable 
thereat. The nut 30 threaded on the sleeve 12 includes a radially inwardly 
projecting collar 31 at its rear end, the collar 31 encircling an aperture 
32 which has an internal diameter larger enough for freely passing 
therethrough the corrugated conduit 1 but smaller than the maximum 
external diameter of the nipple 20 so that the collar 31 is to be in 
abutting engagement with the rear end of the nipple 20. 
In assembling the coupling, the first step is to extend the end portion of 
the corrugated conduit 1 through the nut 30 and to separate the nipple 20 
into two semicylindrical halves 22 by cutting the hinge portion 23, which 
halves 22 are then placed about the end portion of the conduit in such a 
manner as to leave a few row of corrugations at the extreme end of the 
conduit 1 to project beyond the forward end of the nipple 20 and to 
register the serrations 21 into mating engagement of the corrugations of 
the conduit 1. The end portion of the conduit 1 thus clamped by the nipple 
20 is inserted together with the latter into the conduit receiving bore 15 
as the hexagonally shaped nipple 20 being guided by the correspondingly 
shaped conduit receiving bore 15. Thereafter, the nut 30 is threaded on 
the sleeve 12 with the collar 31 abutting against the rear end of the 
nipple 20. Advancing or rotating the nut 30 presses the nipple 20 and the 
conduit 1 held thereby deep into the sleeve 12 to thereby force the end of 
the conduit 1 into pressing contact with the shoulder 16, at which 
occurrence the corrugations left projecting beyond the nipple 20 are 
collapsed between the forward end of the nipple 20 and the shoulder 16 so 
as to provide an effective seal around the entire periphery of the conduit 
end therebetween even though the end of the conduit 1 is not cut exactly 
square. It is to be noted at this time that since the split nipple 20 is 
cut into the two semicylindrical halves 22 which are symmetrical to each 
other they can be successfully placed about the end portion of the conduit 
1 even if one of them might be reversed in its longitudinal direction at 
the situs of the assembling, facilitating the assembling procedures. 
Formed at the juncture of the shoulder 16 and the conduit receiving bore 15 
is an annular groove 17 receiving therein a sealing ring or O-ring 18 for 
improving the sealing effect between the shoulder 16 and the conduit end. 
The sealing ring 18 has an internal diameter slightly smaller than the 
conduit 1 in order that the collapsed end 2 of the conduit 1 is press 
fitted into the sealing ring 18 to elastically deform it radially 
outwardly when the conduit 1 is pressed against the shoulder 16. The 
external diameter of the sealing ring 18 is larger than the minimum 
external diameter of the nipple 20 so that the sealing ring 18 has its 
side in abutting relation to the forward end of the nipple 20. Thus, the 
sealing ring 18 is axially compressed by the front end of the nipple 20 to 
be thereby elastically deformed radially so as to provide tight sealing 
engagements between the sealing ring 18 and the corrugated end 2 of the 
conduit 1 as well as between the sealing ring 18 and the walls of the 
groove 17, assuring a complete seal between the conduit 1 and the sleeve 
12 or the main tubular body 10. The sealing ring 18 may be of circular, 
rectangular or any suitable section for ensuring the above sealing effect. 
First and second modifications of the above embodiment are shown 
respectively in FIGS. 5 and 6 and in FIGS. 7 and 8, these modifications 
being identical in construction to the above embodiment except for the 
external configuration of the nipple 20A and 20B as well as the internal 
configuration of the associated conduit receiving bore 15A and 15B of the 
sleeve 15. For easy understanding, the like parts are designated by like 
numerals as in the above embodiment. In these modifications the nipples 
20A and 20B are shaped to have an star-shaped cross section characterized 
respectively by a larger number of sharpened ribs 25A and by a smaller 
number of rounded ribs 25B both of which are evenly spaced 
circumferentially. The conduit receiving bores 15A and 15B of the 
modifications are correspondingly shaped, permitting the respective 
nipples 20A and 20B to be slidable but unrotatable within the sleeve 12. 
Likewise in the above embodiment, each of the nipples 20A and 20B is 
provided with a slit 24A, 24B and thin-walled hinge portion 23A, 23B by 
which it can be separated into two semicylindrical halves symmetrical to 
each other. 
It is contemplated that still other modifications and changes can be made 
in the coupling disclosed without departing from the scope of the 
invention.