Coupling for flexible metal tubes

Abstract: The device comprises: an adaptor (11) meant to connect to the cock or the like and adapted to hermetically receive the end of the tube (T) or nipple (PG); a threaded annular element (12) adapted to cooperate with a corresponding threaded portion (11b) of the adaptor to anchor the tube or nipple thereto; a sealing element and an axial anchoring element, which are interposed between the annular element (12,120) and the tube or nipple. The axial anchoring element (13,13',13'',13''' ; 130,130') is constituted by a metallic ring that is allowed to flex radially by a longitudinal cut, contrasts against an abutment (12a) of the annular element (12), and performs the axial retention of the tube (T) or of the nipple (PG) by partial engagement, in its minimum-diameter configuration, of a groove (G) or respectively of the tip rib of the tube or nipple.

Description: The present invention relates to a hermetic coupling device particularly for the jointing, by means of threaded tightening elements, of flexible metallic tubes with parallel corrugations and of nipple end fittings provided with protruding circular ribs to cocks and end adaptors in general. More specifically, the invention relates to a coupling device that comprises the following cooperating elements: a male or female adaptor to be connected to a generic threaded end fitting, for example a cock, and adapted to hermetically accommodate the end of the corrugated tube or the nipple; a female or, respectively, male threaded annular tightening element adapted to cooperate with a corresponding threaded portion of the adaptor to anchor the end of the corrugated tube or the nipple to said adaptor; a hermetic sealing element interposed between the adaptor, or both the annular element and the adaptor, and the tube or nipple. Conventional coupling devices of the specified type are substantially divided into two categories: those of the so-called "cable clamp" type, wherein both mechanical anchoring and sealing are provided by radial action on the end of the tube or nipple to be connected, and those with a front seal, wherein the mechanical anchoring is of the axial type. In devices of the first type, the retention and hermetic sealing element, constituted by a ring of typically elastomeric or polymeric flexible material interposed between respective abutments of the annular element and of the adaptor, is deformed radially by the locking of said annular element to clamp the end of the corrugated tube or the nipple, thus providing their axial anchoring with respect to the adaptor as well as the hermetic tightness of the coupling. The greatest drawback of this type of conventional coupling devices is the unreliability of the mechanical retention against extraction of the tube or nipple, which is mainly due to aging of the material of the hermetic sealing element (which occurs particularly rapidly in a corrosive environment). Furthermore, said devices, having no positive elements for mutual abutment between the annular element and the adaptor, do not give the person who assembles them the perception of when the tightening limit is reached, to the obvious detriment of correct installation of the device. In devices with a front hermetic seal, the axial anchoring element, which is separate from the hermetic sealing element, is typically constituted by two half-rings, which are accommodated in a groove of the corrugated tube and protrude radially with respect thereto to be engaged by an abutment of the annular element and transmit to the tube the axial tightening thrust produced by said annular element. Hermetic sealing is entrusted to a flexible front gasket that rests on the adaptor and receives, in forced contact engagement, the end of the tube. This second type of conventional coupling device, too, has several drawbacks, and substantially a considerably troublesome installation, caused by the difficulty in keeping the half-rings in place during the assembly of the device, and the need to have half-rings that are perfectly machined and calibrated according to the geometric features of the corrugated tube; but above all, the greatest drawback is constituted by the substantial lack of adaptability of these devices to nipple end fittings, which have no grooves capable of receiving and accommodating said half-rings. DE-C-886 686 discloses a device for coupling flexible tubes to rigid tubes which includes a sleeve which is disposed at the end of the flexible tube and which surrounds a rubber ring, which is pressed against the end of the rigid tube, by means of an elastic ring which is arranged completely in a groove of the end of the rigid tube. US-A-5 080 405 discloses a corrugated pipe coupling which employs a cut metal seal ring also arranged completely in a groove of on of the tubes to be connected. A principal aim of the present invention is substantially to eliminate the drawbacks of the above mentioned conventional coupling devices, and within the scope of this general aim, the present invention has the following important particular objects: to provide a device capable of ensuring maximum reliability and durability, in terms both of hermetic sealing and of mechanical anchoring of tubes or, equally, of nipple end fittings; to provide a device that is structurally simplified and easy to apply and manufacture and is therefore economically advantageous; to provide a device wherein one or more components have a standardized structure and therefore are also commercially available, to the further advantage of economy and practicality in the application of said device; to provide a coupling device that is completely free from degradation of the mechanical anchoring of the tube or nipple to be connected and is therefore particularly adapted for the connection of household heating appliances to the fuel gas distribution system, and for the connection of flexible metallic tubes for transporting fluids at medium pressure. According to the present invention, this aim as well as these and other important objects are achieved with a coupling device having the specific features of claim 1. Substantially, the invention is based on the use of an axial anchoring element interposed between the annular element of the device and the tube or nipple to be connected; said anchoring element is constituted by a metallic ring that is allowed to flex radially by a longitudinal cut and acts as an axial retainer by partially engaging, in its minimum-diameter configuration, a groove of the tube or a protruding rib of the nipple to be connected. The cross-section of the ring, which is quadrangular, circular, or has another profile, is therefore significantly small and allows to provide a highly flexible ring that can be easily fitted, as will become apparent hereinafter, on the corrugation of the tube or on the conical tip of the nipple without permanent deformations and requires a limited flexing force. Said ring cooperates with an abutment of the tightening ring and transmits the axial thrust of the annular element to the tube or nipple, thus forcing the end of the tube or nipple into contact engagement with a sealing gasket that abuts against the adaptor, when the annular element is screwed on said adaptor. According to an embodiment of the invention, the anchoring ring is separated from the annular tightening element and is fitted independently on the tube or nipple, whereon the annular tightening element has been fitted beforehand. According to a constructive different embodiment, which is particularly advantageous in terms of easy assembly and reduction of loose components, the anchoring ring is included in a groove of the annular tightening element, which is thus provided to the user complete with said ring and is fitted, together with said ring, on the tube or nipple to be connected. Further characteristics and advantages of the device according to the invention will become apparent from the following detailed description and with reference to the accompanying drawings, given only by way of non-limitative example, wherein: figure 1 is an axial sectional view of the coupling device applied to a flexible metal tube with parallel corrugations; figure 2 is a perspective detail view of the anchoring ring; figure 3 is a sectional view, similar to figure 1, of a different embodiment of the invention; figure 3a is a partial sectional view of the anchoring ring, according to a further embodiment; figure 4 is a sectional view, similar to figure 1, of the coupling device applied to a nipple end fitting; figure 5 is a sectional view, similar to figure 1, of a further embodiment of the invention; figure 6 is a sectional view, similar to figure 4, of another embodiment of the invention. In figure 1, the coupling device 10 comprises a male adaptor 11, of a standardized type, with a threaded seat 11a meant to couple with a generic end fitting (not shown), for example to the threaded end of a dispenser cock or faucet, and a threaded tang 11b adapted to receive a correspondingly threaded annular tightening element 12. The annular element 12 is fitted, so as to be freely slideable axially, on the end of a flexible metal tube T of the type with parallel corrugations, which by means of the device 10 must be hermetically connected to said faucet or other generic threaded end fitting. For this purpose, an axial mechanical anchoring element is interposed between the ring 12 and the tube T and is constituted by a metallic ring 13, which is allowed to be flexible in a radial direction by a longitudinal cut 13a (figure 2). The ring 13 provides axial retention by partially engaging, when it is deformed in its minimum-diameter configuration, a groove G of the tube T. The ring 13, which has a quadrangular cross-section in the example of figure 1, in fact only partially penetrates in the groove G, engaging between two adjacent corrugations of the tube T by an extent that is limited but sufficient to transmit to said tube an axial stress that is uniformly distributed along its entire circumference. On one hand, this requires no special machining of the ring, and on the other hand, it allows to maintain the cross-section of said ring within narrow limits, so as to give it high radial elasticity. Accordingly, the ring 13 can be easily fitted to the tube T, requiring a limited force to be deformed elastically in order to increase its inside diameter to make it pass over the corrugation of the tube T. An abutment 12a is formed on the annular element 12 and is adapted to engage the ring 13 to force the tube against the adaptor 11 when said annular element is screwed and tightened on the tang 11b of said adaptor. The abutment 12a is located on the bottom of a cylindrical retention seat 12b delimited by a corresponding cylindrical wall; when the device is assembled, said wall prevents the ring 13 from widening and prevents the consequent accidental disengagement of said ring from the groove G. A frustum-shaped adaptor 12c, arranged along the continuation of the cylindrical wall of the seat 12b, facilitates, during assembly, the entry of the ring in the cylindrical retention seat and its engagement in the groove G of the tube T. An annular gasket 14 abuts against the front wall of the tang 11b, and the end of the tube T is forced hermetically against it by the tightening action of the annular element 12. The gasket 14 can be made of flexible material, or of soft metal, and can also be of a composite metallic-elastomeric type which is the subject of a parent Industrial Utility Model in the name of the same Applicant. The embodiment of figure 3, wherein similar or corresponding parts are designated by the same reference numeral, differs from what has been described above in that the ring 13' has a circular cross-section, in order to avoid possible incisions of the tube T caused by concentration of stresses on the edges of the quadrangular ring. In this case, too, an abutment 12a is provided on the annular element 12 to push the ring axially, as well as a frustum-shaped adaptor 12c that directly couples to the abutment 12a and simultaneously prevents the widening of the ring and transmits the tightening force thereto for its forced and partial engagement in the groove G of the tube. The embodiment of figure 3a shows a ring 13" having instead a substantially Y-shaped cross-section. Said ring is characterized by curved front chamfers 13b,13c capable of coupling to two adjacent corrugations of the tube T to uniformly distribute both the axial thrust and the radial tightening force; the ring 13" is particularly adapted for use in devices 10 for jointing tubes for fluids at medium-high pressure and therefore with a high tightening torque. The embodiment of figure 4 relates to a device 100 for the coupling of a nipple PG to a generic threaded end fitting, which is not shown. According to this embodiment, the adaptor 110 is of the female type and receives, in a threaded seat 111, the correspondingly threaded hollow tang 121 of the tightening ring 120. The cavity of the tang accommodates the nipple PG so that it can slide axially; said nipple is provided, in a per se known manner, with protruding circular ribs 128 and with a conical tip 129. The ring 130 is fitted on the nipple PG after the elastic deformation required to allow said ring to pass beyond the conical tip 129. In its minimum-diameter configuration, the ring 130 instead partially engages the protruding raised portion of the conical tip 129 and transmits to the nipple the axial tightening thrust received from the annular element 120. For this purpose, in a manner that is fully similar to the one described with reference to figure 1, the end of the tang 121 of the annular element is provided with an abutment 122 surrounded by a cylindrical seat 123 for containing the ring; said seat is connected to a frustum-shaped flared portion 124 adapted to facilitate the entry of the ring 130 in the cylindrical seat 123. The conical tip 129 of the nipple PG is forced, by the tightening of the annular element 120, into forced contact engagement against a corresponding abutment 112 of the adaptor 110 and engages, to provide a hermetic seal, a gasket 140 of the O-Ring type that is contained in a groove 141 of said adaptor. In the above described embodiments, the ring 13, 13', or 13" and 130 is separated from the respective annular tightening element 12,120. Accordingly, the devices 10,100 are assembled by first fitting the ring 12,120 on the tube T or respectively on the nipple PG and then fitting the ring 13,130, after deforming it elastically. Then the annular element is tightened on the adaptor 11,110, and this tightening action, in addition to tightening the ring, by making it assume its minimum-diameter configuration, forces the tube T, or respectively the nipple PG, into contact engagement with the adaptor 11,110, achieving the axial mechanical engagement of the connection and sealing it hermetically. In the different embodiments of figures 5 and 6, which are particularly advantageous in terms of easy assembly and reduction in loose components, the anchoring ring is built into the annular tightening element, which is thus provided to the user complete with said ring. For this purpose, the annular element 12" of the device 10" of figure 5 is provided with a groove 20 which is connected at one end to the frustum-shaped adaptor 12c described above and is delimited, at the other end, by an abutment 21 the inside diameter Φ1 whereof is slightly smaller than the outside diameter Φ2 of the ring 13'" in its minimum-diameter configuration. In these conditions, the ring 13"', which is initially forced inside the groove 20, is subsequently unable to leave it. On the other hand, the depth of the groove 20, that is to say, the maximum diameter Φ3 of said groove, is chosen so that it is slightly greater than the diameter that the ring 13" reaches, by deforming elastically, to move over and beyond the corrugations of the tube T when the annular element 12" is fitted on said tube, and in this manner the groove 20 does not interfere with the ring, allowing its correct expansion. Likewise, and for the specified purpose, a groove 20' is formed in the tang 121' of the annular element 120' of the device 100' of figure 6; said groove is connected to the abutment 122' for the ring 130' by a frustum-shaped flared portion 124' and is delimited by a front collar 125' for the stable retention of the ring. The depth of the groove 20', that is to say, its maximum diameter Φ3, is also chosen with the criterion of allowing the free expansion of the ring 130' to move beyond the conical tip 120' of the nipple PG'. Of course, without altering the concept of the invention, the details of execution and the embodiments may be altered extensively, with respect to what has been described and illustrated by way of non-limitative example, without thereby abandoning the scope of the invention as defined by the appended claims, wherein the reference numerals are given only for the sake of better comprehension. Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims: Hermetic coupling device and flexible metal tube or nipple end fitting both with parallel corrugations, particularly for the jointing of said flexible metal tubes (T) or nipple end fittings (PG) to cocks and the like, comprising: an adaptor (11, 110) for connection to the cock or the like, said adaptor being adapted to hermetically receive the end of the tube (T) or nipple (PG); a threaded annular element (12,120) that is adapted to cooperate with a corresponding threaded portion (11b,111) of the adaptor to anchor said tube or nipple thereto; a sealing element (14,140) and an axial anchoring element, which are interposed between the annular element (12,120) and the tube or nipple; said axial anchoring element (13,13',13",13'"; 130,130') being constituted by a metallic ring that is allowed to flex radially by a longitudinal cut (13a) and contrasts against an abutment (12a,122) of the annular element (12,120), characterized in that said metallic ring performs the axial retention of the tube (T) or of the nipple (PG) by partial engagement, in its minimum-diameter configuration, of a groove (G) or respectively of the tip rib (129) of said tube or nipple such that the inside of said metallic ring is radially spaced from the bottom of the groove in its minimum-diameter configuration, said ring being partially accommodated in a cylindrical seat (12b,123) of the annular element (12,120). Coupling device according to claim 1, characterized in that the cylindrical wall of said seat (12b,123) prevents, when the device is assembled, the widening of the ring and its consequent disengagement from the groove (G) of the tube (T) or from the rib (129) of the nipple (PG). Coupling device according to claims 1 and 2, characterized in that the cylindrical wall that delimits the cylindrical seat (12b,123) for the retention of the ring (13,130) in the annular tightening element (12,120) continues with a frustum-shaped connecting portion (12c,124) adapted to facilitate, during assembly, the entry of the ring (13,130) in the cylindrical retention seat (12b,123) and its engagement in the groove (G) of the tube (T) or with the tip rib (129) of the nipple (PG). Coupling device according to claim 1, characterized in that it comprises a male adaptor (11) whereon an annular gasket (14) constituting said sealing element abuts, the end of the corrugated tube (T) being forced against said gasket, to provide a hermetic seal, by the tightening action of the annular element (12) on said adaptor (11). Coupling device according to claim 4, characterized in that the gasket (14) is constituted by one of the following materials: elastomeric material, reinforced polymeric material, soft metal, composite metal-elastomeric material. Coupling device according to claim 1, characterized in that it comprises a female adaptor (110) which accommodates, in a threaded seat (111), the correspondingly threaded hollow tang (121) of the annular tightening element (120); in that the tang of the annular element accommodates, so that it can slide axially, the nipple (PG) whereon the axial retention ring (130) is fitted; and in that the conical tip of the nipple (PG) is forced, by the tightening of the annular element (120), against a corresponding abutment (112) of the adaptor (110) and engages, to provide a hermetic seal, a gasket (140) of the O-Ring type, constituting said sealing element, that is contained in a groove (141) of said adaptor. Coupling device according to claim 1 and any one of claims 2 to 6, characterized in that the axial anchoring ring (13,13" ; 130,130') has a quadrangular cross-section. Coupling device according to claim 1 and any one of claims 2 to 6, characterized in that the axial anchoring ring (13') has a circular cross-section. Coupling device according to claim 1 and any one of claims 2 to 6, characterized in that the axial anchoring ring (13") has a substantially Y-shaped cross-section, with curved front chamfers (13b,13c). Coupling device according to claims 1 to 9, characterized in that the axial anchoring ring (13,13'; 130) is separate from the annular element (12,120,12",120"); said ring, during assembly, being fitted independently on the tube (T) or nipple (PG) whereon the annular element is fitted beforehand. Coupling device according to claims 1 to 9, characterized in that the axial anchoring ring (13"',130') is included in a groove (20,20") of the annular element (12",120') in a preassembled relationship; the annular element being supplied to the user complete with said ring and being fitted therewith on said tube (T) or nipple (PG). Coupling device according to claim 11, characterized in that the minimum diameter (Φ1) of the groove (20,20') is smaller than the minimum diameter (Φ2) of the anchoring ring (13"',130') in order to retain said ring, and in that the maximum diameter (Φ3) of the groove is chosen so that its size allows the elastic expansion that the anchoring ring undergoes to move over and beyond the corrugations of the tube (T) or, respectively, the protruding ribs of the nipple (PG).

Inventors: CASTELLI SERGIO, CASTELLI, SERGIO
Applicants: CASTELLI SERGIO, CASTELLI, SERGIO
Application year: 1995
Main classification: F16L33
IPC codes: F16L19, F16L37, F16L25, F16L33