ITBO20100753A1 - METHOD FOR THE REALIZATION OF A HYDRAULIC FITTING FOR FLEXIBLE HOSES AND HYDRAULIC FITTING MADE WITH SUCH A METHOD. - Google Patents

Description

DESCRIPTION

Attached to a patent application for INDUSTRIAL INVENTION entitled:

METO DO FOR THE REALIZATION OF A HYDRAULIC FITTING FOR FLEXIBLE HOSES AND A HYDRAULIC FITTING MADE WITH THE SAID METO DO.

The present invention relates to a method for making a hydraulic connection for flexible pipes, and a hydraulic connection made with said method.

The present invention finds particular application in the construction of hydraulic systems, in particular in the fields of earthmoving machinery, agriculture, industrial vehicles, hydraulic cranes, forklifts, construction machinery, machine tools, and other industrial applications. .

It should be noted that the hydraulic circuits to which the present invention refers are of the type under pressure, and more precisely, in use, they fall within a range of pressures comprised between vacuum (for suction pumps) and 500 bar.

The hydraulic fittings for flexible pipes under pressure are those components positioned at the end of a flexible pipe to allow the coupling of this pipe with a valve or a junction of the hydraulic circuit.

In the known art, these hydraulic fittings are mainly constituted by a tubular body coupled to a bush, for connection with a flexible pipe, and rotatably connected to a free nut for coupling with a further component of the hydraulic circuit.

More precisely, the tubular body develops along its own direction of development between two opposite ends and is coupled coaxially to the bush by means of a mutual coupling portion.

In particular, the tubular body is inserted into the bush until the reciprocal coupling portions are facing each other.

Δ this point, by means of a special press, the bush is pressed around the tubular body to engage the coupling portions and irremovably constrain the two bodies, defining a gap between them.

In fact, it should be noted that the bush also has a substantially tubular conformation and in detail it has an internal through cavity of increasing diameter, starting from the coupling portion away from it.

In this way, once the bush has been mounted on the tubular body, the aforementioned interspace remains defined between the two bodies, ie a free circular crown between an internal surface of the bush and an external surface of the tubular body.

In use, the flexible tube is inserted into the aforementioned circular crown and kept in position both by means of the radial pressing of the bush and by the presence of gripping elements made inside the bush and outside the tube.

The free nut, on the other hand, is rotatably coupled to the tubular body at a head of this tubular body, protruding from the bush.

The function of the free nut is to allow the coupling of the fitting with other components of the hydraulic circuit by screwing the nut itself, avoiding the risk of subjecting the hose to torsion.

In the known art there are mainly two methods for manufacturing the tubular body.

A first method mainly provides for machining by chip removal, while a second method provides for obtaining the coupling portion between the tubular body and the bushing by drawing.

In detail, the first method provides for the provision of a metal rod, ie a solid metal cylinder, from which the above tubular body is obtained by chip removal.

In particular, the round is completely drilled and turned externally to make both the gripping elements and the coupling portion.

In particular, the coupling portion is made by the turning tool and is defined by a circular groove which extends circumferentially around the tubular body.

In this case, the bushing has its own coupling portion which is counter-shaped to this groove to engage it once it has been radially pressed.

Disadvantageously, a manufacturing method of this type entails numerous technological disadvantages.

First, the method involves the generation of a large amount of screech (about 60% of the raw materials) that is difficult to reuse and laborious to store.

Furthermore, the repeated and frequent tool changes, due to the great mechanical and thermal stresses that are created between tool and piece, involve a considerable cost for the manufacturer, in terms of maintenance and setup times of the machines.

It should also be borne in mind that about half of the market for hydraulic fittings is of the curved type, ie in which the tubular body, once machined, is folded back on itself by 30 °, 45 °, 90 ° or more.

Considering that the method in question involves the processing of an untreated metal rod, to give the fitting a good mechanical resistance it is necessary to subject it to a specific heat treatment (annealing), with further waste of time and storage costs.

As already mentioned previously, in the known art a method is also used which provides for the realization of the coupling portion of the tubular body by drawing.

Disadvantageously, this method, while solving some of the problems related to the first method, introduces new ones which are equally disadvantageous for the manufacturer.

In particular, considering the small thickness of the tubular body of the fittings, the drawing process is particularly critical.

In fact, it is common to create cracks or micro-cracks in the drawn points that affect the quality of the fitting and often prevent its correct functioning.

Furthermore, the strong stress imparted by the drawing tool forces the manufacturer to use tubular bodies of particular quality, that is, not welded, since the drawing could easily damage the welding seam of the tube, breaking it.

In this context, the technical task underlying the present invention is to propose a method for manufacturing a hydraulic connection for flexible pipes which overcomes the aforementioned drawbacks of the known art.

In particular, it is an object of the present invention to provide a method for producing an effective and economical hydraulic connection for flexible pipes.

A further object of the present invention is to propose a method for making a hydraulic connection for flexible pipes that is particularly simple and fast.

Furthermore, it is an object of the present invention to provide a hydraulic connection for flexible pipes which is cheap and easy to manufacture.

The specified technical task and the specified aims are substantially achieved by a method for manufacturing a hydraulic connection for flexible pipes and a hydraulic connection, comprising the technical characteristics set out in one or more of the appended claims.

Further characteristics and advantages of the present invention will become clearer from the indicative, and therefore non-limiting, description of a preferred but not exclusive embodiment of a method for manufacturing a hydraulic connection for flexible pipes, as illustrated in the accompanying drawings in which:

Figure 1 is a side view of a hydraulic fitting for flexible pipes according to the present invention, with some parts removed for clarity of description;

- figure la is a detail of the connection of figure i;

- figure 2 is a further embodiment of a detail of the fitting of figure 1.

With reference to the attached figures, the number 1 indicates a hydraulic connection for flexible pipes made with the method according to the present invention. It should be noted that the hydraulic circuits to which the present invention refers are of the type under pressure, and more precisely, in use, they fall within a range of pressures comprised between vacuum (for suction pumps) and 500 bar.

The method preliminarily comprises a step of preparing a tubular body 2, developing along its own main development direction "A" between its own first 2a and its own second end 2b.

The tubular body 2, defined by a metal tube having an internal through cavity 3, has an internal surface 2c and an external surface 2d.

Preferably, the tubular body 2 is made of seamless metal tube steel.

In particular, the tubular body 2 can be made of ST37.4, ST52 or ST60 steel.

Alternatively, this body can be made of welded steel for metal pipes, for example of the KST590 type.

Preferably, the tubular body 2 is a welded pipe that has been removed.

In other words, the tubular body is made according to a process which includes the following steps:

- preparation of a metal sheet;

- bending of said sheet to face two opposite end flaps;

- making a weld bead between the two aforementioned edges to make the welded pipe.

Furthermore, to obtain a good surface quality, the weld bead is processed to remove excess material and give the pipe, both internally and externally, a circular geometry.

In other words, the tube is "scuffed" downstream of the weld.

Advantageously, the welded pipes are particularly cheap and easy to find for the manufacturer of hydraulic fittings.

Alternatively, however, it is possible to use a tubular body of superior quality, ie made by rolling or extrusion, and therefore not welded.

Furthermore, the tubular body 2 is preferably heat treated, in particular annealed, upstream of the processes to which it is subjected in the method according to the present invention.

Advantageously, this allows its shape and / or curvature to be varied to possibly obtain curved fittings, with curvatures ranging from 10 ° to 180 ° and beyond, and preferably from 30 ° to 90 °.

After having prepared the tubular body, the method provides for a step of machining the external surface 2d of the tubular body 2.

In particular, the aforementioned processing step is divided into at least two sub-phases, i.e. the step of making a plurality of circumferential grooves 4 on the external surface 2d of the tubular body 2 and the step of making a portion on said external surface 2d 5 coupling with a bushing 6.

The step of making the coupling portion 5 with the bushing 6 provides for deforming the external surface 2d of the tubular body 2, in an intermediate zone, to allow the engagement between the tubular body and a bushing 6 placed around it and better described in continuation of this description.

The conformation of the coupling portion 5 will be better clarified hereinafter, since it is a direct function of the processing steps to which the tubular body 2 is subjected.

In this regard, in the method according to the present invention, the step of making the coupling portion 5 is carried out by rolling the outer surface 2d of the tubular body 2.

Consequently, the coupling portion 5 is made by plastic deformation, without chip removal.

Rolling is in fact a process obtained thanks to a strong pressure on the surface to be machined by one or more rolling tools (not shown), suitably constructed and arranged.

These rolling tools radially compress the tubular body 2 beyond its limit of elasticity causing a permanent deformation of the external surface 2d.

In the preferred embodiment, each rolling tool comprises one or more pressure rollers adapted to press against the outer surface 2d of the tubular body 2 to deform it.

Advantageously, the presence of the rollers considerably reduces the stresses arising between the tool and the piece, extending the life of the tool itself and at the same time decreasing the downtime due to maintenance.

In this way, machine downtimes due to tool changes are reduced by almost two hundred times.

In a first embodiment, the step of making the coupling portion 5 comprises the sub-steps of:

- preparation of the rolling tool;

rolling of the outer surface 2d of the tubular body 2 performed by means of the rolling tool to form at least one lateral projection 10 of the tubular body 2.

It should be noted that the projection 10 defines at least in part the coupling portion 5.

In other words, the roller, by pressing on the external surface 2d, creates a recess in this surface and by rotating it guides the flow of deformed material in the direction of rotation, generating the protrusion 10.

In this embodiment, the rolling tool is designed to give the projection 10 a substantially annular development.

In other words, the projection 10 defines a radially projecting annular frame of the tubular body 2. It should be noted that this annular frame has a central axis corresponding to the main development axis "A" of the tubular body 2.

With reference to the attached figures, it should be noted that the rolling process involves a small narrowing of the cavity 3 of the tubular body 2.

In the illustrated embodiment, in fact, a small boss is visible on the internal surface 2c of the tubular body 2, in correspondence with the coupling portion 5.

Preferably, during the rolling step the rolling tool forms a further annular projection 11 adjacent to the projection 10.

More preferably, the projection 10 and the further projection 11 are arranged in succession one immediately downstream of the other.

In this way, between the two protrusions a receiving seat is defined which can be coupled with a corresponding tooth 16 of the bush 6.

It is possible to provide a single rolling tool which produces the projection 10 and the further projection 11 in successive steps.

Alternatively, a pair of rolling tools is operated simultaneously to form both protrusions 10, 11 simultaneously.

In the illustrated embodiment, the annular projections 10, 11 define a sawtooth profile of the coupling portion 5 of the tubular body 2.

In a second embodiment according to the present invention, the step of making the coupling portion 5 comprises the sub-steps of:

- preparation of the rolling tool, similarly to before;

rolling of the outer surface 2d of the tubular body 2 by means of the rolling tool to make at least one circumferential recess 13 on the tubular body 2;

- application of at least one elastic coil 14 (or metal pin) in the circumferential recess 13 to define the coupling portion 5

In other words, instead of making the protrusion by rolling, this second embodiment provides that the rolling tool simply makes a circular channel (recess 13) which extends circumferentially along the periphery of the tubular body 2.

In this recess 13 the elastic coil 14 is only subsequently applied.

Obviously, the elastic coil 14 has a greater thickness than the depth of the recess 13 so as to protrude from the external surface 2d of the tubular body 2 and perform the same functions as the projection 10 of the first embodiment.

Alternatively, the elastic coil 14 can be replaced by a non-elastic metal pin (not shown) inserted between the bushing and the recess 13 only after having positioned the bushing 6 around the tubular body 2, as will be better clarified hereinafter.

The step of making a plurality of circumferential grooves 4 on the outer surface 2d of the tubular body 2 is carried out in an area of the tubular body 2 proximal to the second end 2b with respect to the coupling portion 5.

The circumferential grooves 4 are substantially circular channels which run circumferentially around the tubular body 2.

Preferably, each of these circumferential grooves 4 has a central axis corresponding to the main development axis "A" of the tubular body 2.

In the illustrated embodiment, the grooves 4 are arranged in succession starting from a zone proximal to the second end 2b of the tubular body 2, approaching the first end 2a.

In other words, the succession of grooves 4 develops starting from the coupling portion 5 approaching the second end 2b of the tubular body 2.

In particular, the grooves 4 are parallel to each other and aligned along the main axis of development "A" of the tubular body 2.

These grooves 4 thus define an insertable portion 7 of the tubular body 2 capable of being inserted and fixed (as will be better clarified hereinafter) in an end portion 8a of a flexible pipe 8 to connect it to other components of the hydraulic circuit.

In this sense, the circumferential grooves 4 increase the grip of the insertable portion 7 on the flexible tube 8.

In fact, by compressing the flexible tube 8 radially, the internal surface of this flexible tube 8 adapts to the grooves, engaging with them.

Similarly to the step described above, also the step of making the circumferential grooves 4 is carried out by rolling the outer surface 2d of the tubular body 2.

Consequently, the grooves 4 are made by plastic deformation, without chip removal. More precisely, the phase of making the circumferential grooves 4 includes the sub-phases of:

- preparation of the rolling tool;

- rolling of the external surface 2d of the tubular body 2 performed by means of the rolling tool to make the circumferential grooves 4.

In a first embodiment, the method provides in this phase the use of a single rolling tool active in sequence along the tubular body 2 to make the circumferential grooves 4 in succession.

Alternatively, it is possible to provide a plurality of rolling tools (not shown) which can be placed in succession along the main axis of development "A" of the tubular body 2 to realize the succession of circumferential grooves 4 simultaneously.

It should be noted that the rolling tool can be the same used for making the coupling portion 5, or another tool dedicated to making the circumferential grooves 4. Preferably, the step of machining the external surface 2d of the tubular body 2 is carried out substantially along the entire extension of the external surface 2d.

Even more preferably, the step of machining the outer surface 2d of the tubular body 2 is carried out by rolling along the entire extension of the outer surface 2d.

Advantageously, in this way it is possible to both work and surface finish the tubular body with a single type of machining and with a single type of tool.

In fact, as already mentioned above, the rolling process takes place by plastic deformation, cold and without the removal of material shavings, allowing to obtain extremely smooth surfaces, with a finish equal to or greater than that achievable thanks to the grinding process.

Moreover, rolling also improves the mechanical characteristics of the machined pieces, because it leads to a reorientation of the crystalline elements that make up the surface layer of the piece.

More precisely, the "fibers" of the metal are aligned in the rolling direction, making the surfaces of the treated pieces more homogeneous and resistant to breakage, abrasion and corrosion.

Consequently, the surface finishing phase of the tubular body 2 is embedded between the plastic deformation processes, considerably speeding up the production process.

As already mentioned several times, the hydraulic fitting 1 comprises the bushing 6, shaped to wrap around the tubular body 2 and engage with it, acting as a vice for the flexible tube 8 placed between them (as will be clarified hereinafter).

The bush 6 mainly has a tubular conformation.

In other words, the bush 6 has an internal cavity 6a having at least a portion 6b with a smaller diameter and a portion 6c with a larger diameter.

In the illustrated embodiment, the bush 6 has a flared shape from the smaller diameter portion 6b to the larger diameter portion 6c. Alternatively, the bushing 6 can assume a "cup" shape, in which the base of the "cup" is perforated to define the smaller diameter portion 6b. In order to allow the bush 6 to wrap around the tubular body 2, the portion 6b with a smaller diameter has a larger diameter than the coupling portion 5 of the tubular body 2.

In this light, the method according to the present invention also provides for the steps of:

- predisposition of bushing 6;

insertion of the tubular body 2 into the bushing 2, coaxially thereto, until the portion 6b with a smaller diameter of the bushing 6 faces the coupling portion 5 of the tubular body 2; - radial pressing of the smaller diameter portion 6b of the bush 6 onto the coupling portion 5 of the tubular body 2 to irremovably couple the tubular body 2 to the bush 6.

In the preferred embodiment, the smaller diameter portion 6b of the bush 6 has an internal edge 12 substantially counter-shaped to the coupling portion 5 of the tubular body 2.

In this way, during the pressing step of the bushing 6, the inner edge 12 abuts the coupling portion 5 making the tubular body 2 and the bushing 6 at least axially integral.

More precisely, in the first embodiment, the inner edge 12 of the bushing 6 has a sawtooth profile that is counter-shaped to that of the coupling portion 5.

In the second embodiment, the inner edge 12 of the bushing 6 has a recess substantially specular to the circumferential recess 13 of the coupling portion 5.

Once the bushing 6 has been mounted on the tubular body 2, an annular space is defined between the two in which the end portion 8a of the flexible tube 8 can be inserted.

Furthermore, at the larger diameter portion 6c, the bush 6 has a plurality of teeth 15, each facing a respective circumferential groove 4 of the tubular body 2 to press on the end 8a of the flexible tube 8 inserted in the annular space and fix it.

The method according to the present invention can further comprise a step of bending the tubular body 2 performed downstream of the step of making the coupling portion, but before the step of inserting the tubular body 2 into the bushing 6.

In this way it is possible to obtain the aforementioned curved fittings, which occupy an important slice of the hydraulic fittings market.

The invention achieves the intended purposes and achieves important advantages.

In fact, the method according to the present invention, avoiding the production of scraps and realizing the finishing at the same time as the deformation processes, allows to realize a hydraulic connection for flexible pipes in an economical and fast way.

Furthermore, the possibility of minimizing machine downtime due to tool changes makes machining more economical.

Advantageously, however, the absence of impulsive processing or material removal allows to obtain fittings of excellent quality even if starting from welded tubes, cheaper than those made by extrusion or lamination.

Claims (12)

CLAIMS 1. Method for making a hydraulic connection for flexible pipes, comprising the steps of: - arrange a tubular body (2) developing between its own first (2a) and its own second end (2b); making a plurality of circumferential grooves (4) on the outer surface (2d) of the tubular body (2); said circumferential grooves (4) being arranged in succession along a main development direction (A) of the tubular body (2); - realizing, on said external surface (2d) of the tubular body (2), a portion (5) for coupling with a bushing (6), characterized in that said step of making a plurality of circumferential grooves (4) and said step to realize a coupling portion (5) are implemented by rolling the outer surface (2d) of the tubular body (2). 2. Method according to claim 1, characterized in that the step of making said coupling portion (5) comprises the sub-steps of: - prepare a rolling tool; - rolling said outer surface (2d) of the tubular body (2) by means of said rolling tool, to form at least one lateral projection (10) of said tubular body (2); said protrusion (10) defining at least in part said coupling portion (5). Method according to claim 2, characterized in that said step of rolling the outer surface (2d) of the tubular body (2) comprises the step of giving said projection (10) a substantially annular development. Method according to claim 2 or 3, characterized in that during said rolling step the rolling tool forms a further annular projection (11) adjacent to the projection (10). Method according to any one of claims 2 to 4, characterized in that each annular projection (10, 11) has a sawtooth profile. Method according to any one of the preceding claims, characterized in that it comprises a surface finishing step of the tubular body (2) made by rolling using a respective rolling tool. Method according to any one of the preceding claims, characterized by the fact that the tubular body (2) is a welded pipe which has been removed. 8. Method according to any one of the preceding claims, characterized in that it comprises the steps of: - providing a bushing (6) having an internal cavity (6a) having at least one portion (6b) with a smaller diameter and a portion (6c) with a larger diameter; said portion (6b) having a smaller diameter having a larger diameter than the coupling portion (5) of the tubular body (2); - inserting the tubular body (2) into the bushing (6), coaxially thereto, until the smaller diameter portion (6b) of the bushing (6) faces the coupling portion (5) of the tubular body (2); radially pressing the smaller diameter portion (6b) of the bushing (6) onto the coupling portion (5) of the tubular body (2) to irremovably couple the tubular body (2) to the bushing (6). Method according to claim 8, characterized in that the smaller diameter portion (6b) of the bush (6) has an internal edge (12) substantially counter-shaped to the coupling portion (5) of the tubular body (2). Method according to any one of the preceding claims, characterized in that said step of making a coupling portion (5) comprises the sub-steps of: - prepare a rolling tool; - rolling said outer surface (2d) of the tubular body (2) by means of said rolling tool to make at least one circumferential hollow (13) on the tubular body (2); - applying at least an elastic coil (14) or a metal pin in the circumferential recess (13) to define said coupling portion (5). 11. Hydraulic hose connection, comprising: - a tubular body (2) extending between its own first (2a) and its own second end (2b), having on its own external surface (2d) a plurality of circumferential grooves (4) arranged in succession and a portion (5) coupling with a bushing (6); characterized in that the plurality of circumferential grooves (4) and the coupling portion (5) are made by rolling. Hydraulic fitting according to claim 11, characterized in that the coupling portion (5) is defined at least in part by a pair of annular projections (10, 11) of the tubular body (2); said protrusions (10, 11) being arranged in a mutually coaxial manner and in succession to define a substantially sawtooth profile of the coupling portion (5) of the tubular body (2).