Distributor for continuously feeding abrasive material in a water-jet cutting machine

A machine has a head with a nozzle, a pipe for supplying water under pressure to the nozzle, and a duct for supplying an abrasive agent, and adding it to the jet of water under pressure. The duct has a first duct portion, fixed with respect to the head in the movements of rotation about a main axis, and a second duct portion, which is fixed with respect to the movements of rotation. A rotating distributor connects the first rotating portion with the second fixed portion of the duct for supplying the abrasive agent. The distributor's stator and rotor are rotatably mounted on one another without the interposition of seal rings and define between them an internal chamber that is substantially at atmospheric pressure and from which the abrasive agent drops by gravity to a duct outlet that converges into the pipe for supplying water under pressure.

This application claims priority to IT Application No. TO2009A000732 filed 28 Sep. 2009, the entire contents of which is hereby incorporated by reference.

The present invention relates to machines for cutting with a jet of water with the addition of abrasive material for machining glass, stone, or other materials, of the type comprising one or more cutting heads, which moves along one or more axes and includes a nozzle for emission of a jet of water at extremely high pressure, a pipe extending along a main axis of the head, about which the head is able to turn, for supplying water under pressure to the nozzle, and a duct for supplying to the nozzle the abrasive, for example garnet, which is added to the jet of water under pressure.

In the machines of the type specified above, the addition of the abrasive agent to the jet of water at high pressure enables execution of cutting also on materials with a high degree of hardness.

At the current state of the art, in the aforesaid machines the cutting head is mobile along three mutually orthogonal axes conventionally designated by the letters X, Y, Z and, if required, along a further two axes, one of which is the axis of rotation about the aforesaid main axis, conventionally designated by the letter C and referred to as “fourth axis” and the other intersects the preceding one according to a variable angle, positioned at which is the nozzle for concentration and mixing of the water at extremely high pressure with the abrasive, said axis being commonly designated by the letter B and referred to as “fifth axis”.

In the aforesaid machine, the abrasive is conveyed by means of a flexible pipe set on the outside of the axis Z and of the head, which is subject to bending and torsion following upon the movements of the axis C and of the axis B, with the consequence that the rotation about the aforesaid fourth axis can be performed only in finite mode, i.e., for a maximum angle of approximately 360° or slightly greater, without any possibility of continuous rotation for a number of turns. Said limit in various cases determines a disadvantage above all in terms of quality of the cutting operation on account of the need to make brief stops during machining in order to reposition the nozzle to prevent twisting of the pipe for delivery of the abrasive. Said stops determine a greater abrasion of the material and a consequent lack of constancy of the quality of the cut.

WO 2008/128303 A1 shows a machine for cutting with hydro-abrasive jet, comprising a cutting head including a nozzle for emission of a jet of water under pressure, a pipe extending along a main axis of the head about which the head is able to turn, for supplying water under pressure to the nozzle, and a duct for supplying an abrasive agent and adding it to the jet of water under pressure. The duct for the abrasive agent comprises a first portion of duct fixed with respect to with the head in the movements of rotation about said main axis and a second portion of duct, which is, instead, fixed with respect to said movements of rotation, and a rotating distributor is provided, which connects said first, rotating, portion to said second, fixed, portion of the duct for supplying the abrasive agent.

The main drawback of this known solution lies in that the distributor comprises a stator and a rotor rotatably mounted with respect to one another with the interposition of seal rings. This arrangement is necessary in so far as the abrasive material is forced under pressure towards the outlet from the duct for the abrasive material. However, the relative rotation of the aforesaid elements, in the presence of abrasive material, leads to an early wear of the seal rings, which in effect renders said solution inapplicable.

The object of the present invention is to overcome the aforesaid drawback.

According to its main characteristic, the invention enables solution of the problem described above by that said rotating distributor comprises a stator connected to the fixed portion of the duct and a rotor connected to the rotating portion of the duct, and that said stator and said rotor are rotatably mounted on one another without the interposition of seal rings and define between them an internal chamber which communicates with both of the aforesaid duct portions and is substantially at atmospheric pressure and from which the abrasive agent descends simply by gravity down to an outlet of said duct for the abrasive agent that converges into said pipe for supplying water under pressure.

Thanks to the aforesaid characteristics, during the rotations of the head about the aforesaid main axis the portion of the duct for delivery of the abrasive agent that is fixed with respect to the rotating part of the head turns with the latter about the aforesaid main axis, whilst the aforesaid rotating distributor ensures continuous delivery of the abrasive agent maintaining the communication between said rotating portion of the duct and the fixed portion of the duct. Since supply of the abrasive material is simply entrusted to the gravity, the stator and the rotor of the distributor are rotatably mounted with respect to one another without the interposition of seal rings, so that the drawback of poor reliability and short service life inherent in the known solution discussed above is radically eliminated.

In this way, moreover, the machine according to the invention enables rotations of the head about the aforesaid main axis also for an infinite number of turns during execution of the cutting operation, without any need to make stops that would cause a lack of uniformity of the quality of the cut.

In a preferred embodiment, the invention applies to a machine of the type mentioned above, where the head is mobile along three mutually orthogonal axes X, Y, Z and is moreover able to turn both about the aforesaid main axis, which functions as fourth axis, and about a fifth axis that intersects the fourth axis according to a variable angle.

Of course, the invention is in any case applicable to any type of water-cutting machine, whatever the architecture and the functionality of the machine.

With reference toFIG. 1, the number1designates as a whole a water-cutting machine to which the invention can, for example, be applied. The machine1comprises a fixed bench2, defining a resting surface3for the workpieces. A cross-member4is set above the surface3and is, slidably mounted, like a bridge crane, on guides provided along the two side walls of the bench2. The reference number5designates a carriage, slidably mounted on the cross-member4in the longitudinal direction Y of the cross-member, the longitudinal direction of the bench2along which the cross-member4is displaceable being designated by X. As may be seen more clearly inFIG. 2, the carriage5supports in a slidable way along a vertical axis Z a slide6carrying a machining head, designated as a whole by the reference number7(see alsoFIG. 3).

The head7comprises a nozzle8for delivery of a jet of water at high pressure. The structure of the nozzle8is carried by the slide6, which is able to move in Z via interpositions of two further axes of rotation. In particular, once again with reference to the example illustrated, the slide6supports in cantilever fashion a support9, which carries in rotation an underlying structure10of the head7about a main axis11, parallel to the vertical direction Z, which constitutes the fourth axis of the machine. The structure10is elbow-shaped and supports an underlying support12(see in particularFIG. 3), to which the nozzle8is connected in such a way that it can turn about a fifth axis13that intersects the axis11with a variable angle A.

With reference also toFIG. 4, the nozzle8has an axial passage8afor delivery of a jet of water at high pressure, which receives the water under pressure from a pipe14extending along the axis11and carried by the structure10rotating about said axis. The pipe14consequently turns with the structure10about the axis11during the movements of orientation of the head. Once again with reference toFIG. 4, the top end of the pipe14is in communication with a non-rotating pipe15via a rotary joint16. The means set upstream of the pipe15, for supplying the water at high pressure are not illustrated in the annexed drawings and can be obtained in any known way.

Inserted in the body of the nozzle8is a prod-like end17of a duct19for delivery of an abrasive agent, specifically garnet, to the jet of water at high pressure. The internal passage of the body of the nozzle8in which the prod17is inserted converges in the axial passage8ain such a way that the flow of sand that is fed downwards by gravity is drawn into the flow of water under pressure by an ejecting effect (Venturi effect).

According to a main aspect of the present invention, the duct19for supplying the abrasive comprises a duct portion19a, which is fixed to the structure10with respect to rotations about the axis11, and a portion19b, which is, instead, fixed with respect to rotations about the axis11, since it is fixed with respect to the slide6. In the case of the example illustrated, the first portion19aof the duct extends parallel and immediately adjacent to the pipe14for the water along the axis11, so that during the rotations of the structure10about the axis11the portion19aof the duct19turns like a satellite about the pipe14for the water. Also visible inFIG. 4is part of the structure of the support9fixed to the slide6and the belt transmission20contained therein, by means of which the rotation of a top part10aof the structure10is governed by an electric motor21(visible inFIG. 2).FIGS. 2,3show also part of the assembly22for control of the rotation of the support12about the fifth axis13.

Once again with reference toFIG. 4, the reference number23designates a rotating distributor, which connects the rotating portion19aof the duct19for the sand with the fixed portion19b. The rotating distributor23comprises a stator body24, rigidly connected to the bottom end of the fixed portion19bof the duct19, and a rotor body25(see alsoFIG. 2), connected in rotation to an internal cavity26, which is in turn connected in rotation about the axis11, with respect to the structure9, to the structure10. The stator24and the rotor25are rotatably mounted with respect to one another and define between them the internal cavity26, which is in communication with both of the duct portions19a,19b. The cavity26has an inclined bottom wall27that enables conveyance of the sand coming from the fixed portion19bof the duct towards the outlet of the distributor that is aligned with the rotating portion19a.

As already illustrated above, the cavity or chamber26of the rotating distributor is substantially at atmospheric pressure, and the abrasive material is supplied simply by gravity from the chamber26as far as the outlet of the duct19that converges into the passage14for the water. From this standpoint, particularly advantageous is the inclined surface27, which thus performs the function of hopper. The stator and the rotor of the distributor are rotatably mounted with respect to one another without interposition of seal rings, so that the problem of reliability and service life linked to the wear of said seal rings is solved at the root, without jeopardizing supply of the abrasive material, given that the chamber26is not under pressure.

Thanks to the structure and to the arrangement described above, supply of sand is ensured continuously during the cutting operation, without jeopardizing the possibility of continuous rotation of the structure10of the head about the aforesaid main axis11, or fourth axis, and without any impediment due to the presence of the duct for delivery of the abrasive.

As may be seen inFIG. 4, the bottom end of the portion19aof the duct extends into a flexible pipe19cfor connection to the end prod17inserted in the body of the nozzle.

As is evident from the foregoing description, the machine according to the invention does not require frequent stops during the cutting operation as, instead, is the case of known machines and consequently guarantees a high uniformity of the quality of the cut. Operation of the machine is in general more reliable, without involving, on the other hand, any significant constructional complication.

As already mentioned, the invention is of course applicable to any configuration and architecture of cutting machine which uses a jet of water under pressure with the addition of a flow of abrasive, for example garnet.