Gas cooking appliances coupling bushing and process for applying it onto such appliances

Abstract: Coupling bushing, preferably for gas cooking appliances, such as gas ranges and top cooking plates, said bushing being bored internally for the entire lenght thereof and joined to a short edge of diameter smaller with respect to that of the remaining bushing portion, wherein the bushing inner hole is provided with a threaded portion for connection of at least a gas supply piping and a knurled not threaded portion for connection of at least a tube distributing gas or burner of the cooking appliance. The tube distributing gas (9) is shaped at its end portion (15) with at least a radial projection (16) and a plurality of longitudinal hollows (17) and longitudinal strips (18) distributed alternate from each other, and the longitudinal strips (18) are compressed against said not threaded portion (14) of bushing, inserted on to said strips (18) and said longitudinal hollows (17), under abutment condition of the same against said radial projection (16).

Description: The invention refers to a coupling, preferably for gas cooking appliances, in particular gas ranges and top cooking plates, so shaped as to be able to be coupled to the relative appliances in a mechanical way with few operative steps, by ensuring always an effective gas tightness as well as a high tensile and torsion mechanical strenght. The invention also relates to a process for manufacturing such coupling for gas cooking appliances. From WO 9114894 is known a fitting for attachment to a tube by external swaging. The fitting includes an outer surface that fits within the die of a swaging tool and an inner surface that includes axially spaced annular grooves that bite into the tube upon swaging. A reinforcing ring surrounds the outer surface of the fitting to provide reinforcement. The fitting also has an outer end with a special double tapered configuration, such that the tube and inner surface of the fitting form a wedge that equally distribute the load and increases the tube retention capability of the fitting. The fitting also includes positioning means for positioning the fitting within the dies of the swaging tool and further includes tapered axial grooves on the inner surface of the fitting for presenting torsional movement. The fitting and the tube also have a balanced configuration which minimizes fretzing. The object of the present invention is to realize a coupling, particularly for gas cooking appliances, which has different constructive characteristics and is assembled to the appliances in a manner different than the invention disclosed by WO 9114894, so as to ensure an effective gas tightness as well as a high tensile and torsion mechanical strength. This coupling is made with the constructive characteristics and the applying steps substantially described, with particular reference to the accompanying claims of the present patent. The invention will be understood better from the following description, given solely by way of not-limiting example, and with reference to the accompanying drawings, in which : Fig. 1 shows a perspective view of a coupling according to the invention ; Fig. 2 shows a perspective view of the same coupling of Fig. 1, in a uncoupled condition; Fig. 3, 4 and 5 show schematically the different steps for joining the present coupling to the tube distributing gas and the gas supply piping, in a view cutaway in a longitudinal direction. In the Figures referred to, a bushing 6 of metallic material resisting at high temperatures (of about 350° C- 400° C) is illustrated schematically, the end portion 7 of which is screwed or mechanically secured in another suitable manner to a gas supply piping (not indicated), and the other end portion 8 of which is joined to the tube 9 distributing gas of a gas cooking appliance of conventional type (not shown), such i.e. a gas range, a gas top cooking plate or the like. Such bushing may be also used in combination with liquid or fluid conduits of various kind. As particularly evident from Figs. 1 and 2, such bushing 6 is shaped preferably of cylindrical form, or polygonal or also of any other adequate geometric form , which is internally bored for the entire lenght thereof, and joined to a short edge 10 of reduced diameter with respect to that of the remaining bushing portion 11. In the example referred to, the inner hole 12 of the bushing is provided with a threaded portion 13 for a lenght part of the same bushing, in order to permit the gas supply piping to be gas tigthly screwed, and a not threaded portion 14 which is knurled, assigned to be adapted to and mechanically joined as it will be described with the end portion 15 of the tube distributing gas 9. Besides, such end portion 15 is shaped with at least a projection 16 slightly projected radially along the entire peripheral surface thereof and a plurality of longitudinal hollows 17, distributed for a certain extent in the lenght direction of such peripheral surface, also in the area of the projection 16, and suitably spaced away from each other along all the same peripheral surface, in the present example spaced away from each other in the same measure, thereby delimiting corresponding thin longitudinal strips 18 between one hollow and the next one. In the Figs. 3, 4 and 5 it is shown schematically the applying process of the present bushing on both the tube distributing gas 9 and the gas supply piping. In the first step of the present process, visible from the Fig. 3, it can be noticed that the tube distributing gas 9, whose peripheral surface was rectilinear initially, is shaped with a suitable tool (for example a punching machine) on its end portion 15, thereby forming the radial projection 16 which acts as abutment for the bushing 6, as well as a gas distributing tube short portion 19 on the end zone 20 thereof. In the subsequent second step of the process, visible from the Fig. 4, the bushing 6 is inserted by means of a suitable tool with its edge 10 onto the short portion 19 until the front surface 21 of this edge comes into contact against the radial projection 16 and the front surface 22 of the tube distributing gas is almost coincident with the joining zone 23 between the not threaded portion 14 and the threaded portion 13 of the bushing inner hole 12. Finally, in the subsequent third step of the process, visible from the Fig. 5, a further tool (for example a punch) is inserted inside the threaded portion 13 of both the bushing 6 and the hole 24 of the tube distributing gas, which tool is shaped with an outer profile complemental to that of said hollows 17 and strips 18, and whose insertion determines in the hole 24 of the tube distributing gas the forming of such hollows and strips, as well as the radial expansion of these latter which, therefore, are pushed under pressure against the corresponding inner surface of the bushing hole 12, thereby determining also the radial flaring of the front surface 22 of the tube distributing gas and the consequent deformation of the bushing joining zone 23. Finally, the gas supply piping is screwed on the hole threaded portion 13 of the bushing. In this way, the bushing 6 is joined mechanically tightly with the tube distributing gas 9, without need of weldings, by ensuring a high tensile and torsion mechanical strenght, thanks to the presence of the strips 18 which are pushed under pressure against the inner part of the same bushing. The advantages originated by this invention are : reduction of the manufacturing steps and the used materials, and therefore also considerable reduction of the production costs (about 80% less), elimination of the wastes determined by cracks caused by quick cooling of the weldings previously effected, increasing of productive capacity in the same working times, elimination of cleaning operations and protection against oxidation, which are required by the weldings, as well as easy automation of the process.

Claims: Process for manufacturing a coupling for appliances, preferably gas cooking appliances such as gas ranges and gas top cooking plates, said coupling comprising a bushing(6) and a tube distributing gas (9), said bushing (6) being bored internally for the entire lenght thereof and joined to a short edge (10) with a diameter smaller than that of the remaining bushing portion (11), wherein the bushing inner hole (12) is provided with a threaded portion (13) for connecting at least a gas supply piping on one side and a knurled not threaded portion(14) on the other side for connection of said tube distributing gas (9) or burner of the cooking appliance, the process being characterized in that said tube distributing gas (9), whose peripheral surface was rectilinear initially, is shaped with a suitable tool, for example a punching machine, on its end portion (15), thereby forming along the peripheral surface of said end portion (15) at least a radial projection (16) acting as abutment for said bushing (6) as well as a short tube portion (19) on the end zone (20) thereof; in that said bushing (6) is inserted by means of a suitable tool with its edge (10) onto said short tube portion (19) until the front surface (21) of this edge comes into contact against said radial projection (16) and the front surface (22) of said tube distributing gas (9) is almost coincident with the joining zone (23) between said not threaded portion (14) and said threaded portion (13) of said inner hole (12); and also characterized in that a further tool, for example a punch, is inserted inside said threaded portion (13) of said bushing (6) and the hole (24) of said tube distributing gas (9), so as to form in said hole (24) a plurality of longitudinal hollows (17) and longitudinal strips (18), delimited between one hollow (17) and the next one, which are distributed by a certain extent in the length direction of the peripheral surface of said end portion (15), also in the area of said projection (16), and suitably spaced away from each other along all the same peripheral surface, and characterized in that said further tool determines also the radial expansion of said hollows (17) and said strips (18), which are therefore pushed under pressure against the corresponding inner surface of said bushing inner hole (12), by mechanically joining also said knurled not threaded portion (14) of said bushing (6) with said end portion (15) of said tube distributing gas (9), thereby determining also the radial flaring of said front surface (22) of said tube distributing gas (9) and the consequent deformation of said bushing joining zone (23).

Inventors: CREMONESE ROBERTO, CREMONESE, ROBERTO
Applicants: COPRECI SYSTEMS S R L, COPRECI SYSTEMS S.R.L.
Application year: 2000
Main classification: F16L13
IPC codes: F16L13