APPARATUS AND METHOD FOR WATERJET CUTTING

Abstract

Disclosed is an apparatus for water jet cutting including: a water source; a pump communicating with the water source, generating a high pressure water flow; a tank containing an abrasive material in suspension, including a fluid and abrasive particles dispersed homogeneously in the fluid; and a cutting head in fluid communication with the pump and the tank, the cutting head including a mixing chamber. The tank of the abrasive material in suspension is in communication with the cutting head by an abrasive inlet channel and the cutting head is configured to generate a vacuum pressure that draws the abrasive material in suspension through the abrasive inlet channel toward the mixing chamber to mix the abrasive material in suspension and the high pressure water and form a jet of water and abrasive. Also disclosed is a method for generating a water jet cut that can be implemented with the apparatus.

Claims

1. Apparatus (1) for water jet cutting comprising: a water source (2); pumping means (4), in communication with the water source, to generate a high pressure water flow; a tank (22) containing an abrasive material in suspension (21), wherein said abrasive material in suspension comprises a fluid and abrasive particles dispersed homogeneously in the aforesaid fluid; and a cutting head (10) in fluid communication with said pumping means (4) and said tank (22), said cutting head comprising a mixing chamber (12); wherein said tank (22) is in communication with said cutting head (10) by means of an abrasive inlet channel (23) and said cutting head (10) is configured to generate a vacuum pressure that draws the abrasive material in suspension (21) through said abrasive inlet channel (23) toward the mixing chamber (12) to mix the abrasive material in suspension and the high pressure water and form a jet of water and abrasive substance (15).

2. Apparatus (1) according to claim 1, wherein the abrasive inlet channel (23) is equipped with flow regulating means (27) of the abrasive material in suspension (21).

3. Apparatus (1) according to claim 1, wherein said abrasive material in suspension (21) comprises abrasive particles dispersed in a gelatinous substance.

4. Apparatus (1) according to claim 3, wherein said gelatinous substance comprises at least water and a gelling agent.

5. Apparatus (1) according to claim 3, wherein the volume ratio between the abrasive particles and the gelatinous substance is from 1:4 to 1:8.

6. Apparatus (1), according to claim 4, wherein the volume percentage of the gelling agent in the water is between 0.5% and 5%.

7. Apparatus (1) according to claim 1, wherein said cutting head (10) comprises a focusing tube (14) of the jet with a diameter between 0.4 mm and 1.5 mm, and a length between 100 mm and 200 mm.

8. Apparatus (1) according to claim 1, wherein at said cutting head (10) comprises a focusing tube (14) that includes at least two portions of tube joined by a removable connection element.

9. Apparatus (1) according to claim 2, wherein said flow regulating means (27) are mounted at an outlet of the abrasive material of said tank (22).

10. Apparatus (1) according to claim 9, wherein said flow regulating means (27) comprise an opening, through which the abrasive material in suspension can flow, and a moving partition, associated with control means, adapted to obstruct or partly or totally free the aforesaid opening.

11. Apparatus (1) according to claim 3, further comprising a mixing device (24) to mix the water, the gelling agent and the particles of abrasive material to form the abrasive material in suspension (21).

12. Apparatus (1) according to claim 11, further comprising dosing means (26), associated with said mixing device (24), to dose the quantity of water, of gelling agent and of particles of abrasive material to form the abrasive material in suspension (21).

13. Apparatus (1) according to claim 1, further comprising: a collection container (31) to collect the water and the abrasive material, delivered from the cutting head (10), and the waste material from processing; a recovery and recycling system (30) that includes at least: separation means (33) to separate reusable wet abrasive particles from non-reusable wet abrasive particles and from waste material; and transport means to transfer said wet mass of reusable abrasive particles into the tank (22) of the abrasive material in suspension or into the mixing device (24).

14. Method for generating a water jet cut with a cutting apparatus, comprising the following steps: providing a water source (2); preparing an abrasive material in suspension (21), this latter comprising a fluid and abrasive particles dispersed homogeneously in the aforesaid fluid; pumping the water at high pressure into a mixing chamber (12) of a cutting head (10); generating a vacuum pressure in the mixing chamber (12) to draw the abrasive material in suspension (21) into said mixing chamber (12) through an abrasive inlet channel (23); mixing, in said mixing chamber (12), the pressurized water and the abrasive material in suspension (21); and discharging a jet of water and abrasive material (15) from a focusing tube (14) in communication with the mixing chamber (12).

15. Method according to claim 14, wherein the step of preparing the abrasive material in suspension (21) comprises the stage of mixing the fluid and the abrasive particles.

16. Method according to claim 14, wherein the fluid is a gelatinous substance.

17. Method according to claim 16, wherein the step of preparing the abrasive material in suspension (21) comprises the stage of mixing water, at least one gelling agent and particles of abrasive to form said gelatinous substance in which the particles of abrasive are suspended and dispersed homogeneously.

18. Method according to claim 15, wherein the step of preparing the abrasive material in suspension (21) comprises a further stage, preceding the mixing stage, consisting of dosing the fluid and the abrasive particles.

19. Method according to claim 17, wherein the step of preparing the abrasive material in suspension (21) comprises a further stage, preceding the mixing stage, consisting of dosing the water, the gelling agent and the abrasive particles.

20. Method according to claim 15, wherein the mixing step is carried out in a mixing device (24), said abrasive material in suspension (21) prepared being subsequently conveyed into a tank (22) in fluid communication with the mixing chamber (12).

21. Method according to claim 14, comprising the following steps: collecting at least a part of the jet of water and abrasive delivered from the cutting head (10) in a collection container (31); separating reusable wet abrasive particles from non-reusable wet abrasive particles and from waste material; transferring said wet mass of reusable abrasive particles into a tank (22) of the abrasive material in suspension or into a mixing device.

22. Method according to claim 21, wherein the step of preparing the abrasive material in suspension comprises the mixing of water, at least one gelling agent, said abrasive particles, wet or dry, or of both types.

Description

[0071] Further characteristics and advantages of the present invention will become more apparent from the description of an example of a preferred, but not exclusive, embodiment of an apparatus for water jet cutting illustrated schematically in the accompanying FIG. 1:

[0072] With reference to the FIGURE, the reference number 1 indicates as a whole an apparatus for water jet cutting. As mentioned above, within the context of the present invention the term water must be interpreted extensively, hence with reference to any liquid and, even more generally, fluid, solid or combinations thereof, provided that it is suitable to be treated (compressed, transferred, conveyed) with the normal devices used for a fluid and in particular suitable to be forced inside an orifice of small size, such as the focusing nozzle of the apparatus.

[0073] The apparatus is then supplied with a water source 2 to supply the aforesaid process water to the apparatus. The water source 2 can comprise a tank or a continuous feed line. The source 2 can be equipped with water treatment devices to treat the process water to make it more suitable for use in high pressure pumping apparatus. These treatment devices are well known to those skilled in the art and shall not be described in more detail. A water line 3 connects the water source 2 to pumping means 4.

[0074] Said pumping means 4 can comprise a common waterjet pump, for example an intensifier pump, a reciprocating pump, a direct-drive pump or a servo-electric pump.

[0075] Said pumping means are generally configured to convey the process water at a pressure typically between 3000 and 6000 bar.

[0076] A water infeed line 5 places said pumping means 4 in communication with the cutting head 10 of the apparatus.

[0077] The apparatus 1 further comprises a source, indicated as a whole with 20, of an abrasive material in suspension 21. In the variant illustrated, the source of abrasive material in suspension 20 (hereinafter also only abrasive material), comprises a tank 22 in which the abrasive material in suspension 21 can be deposited. An abrasive inlet channel 23 places the tank 22 in communication with the cutting head 10.

[0078] According to the invention, said abrasive material in suspension comprises a liquid or, preferably, gelatinous substance in which particles of abrasive material are dispersed. Examples of abrasive materials that can be used in the apparatus of the invention are garnet, glass, metal grits based on aluminum or the like.

[0079] A gelatinous substance is particularly advantageous as it allows the abrasive particles to remain suspended, and hence dispersed homogeneously, for several hours, preventing them from precipitating through gravity and accumulating at the bottom, mainly, of the tank 22.

[0080] The abrasive material in suspension can therefore be prepared and stored in a tank of the apparatus ready for use.

[0081] Preferably the suspension is formed with a water-based gelatinous substance.

[0082] More in detail the suspension comprises water and a gelling agent.

[0083] The volume ratio between the amount of abrasive material and of the liquid or gelatinous substance is preferably from 1:4 to 1:8 and more preferably from 1:5 to 1:7.

[0084] According to the invention, the cutting head 10 comprises a body 11 in which a mixing chamber 12 is provided. The mixing chamber 12 is in fluid communication with the water infeed line 5 and with the abrasive inlet channel 23.

[0085] The pressurized water is forced into an orifice 13 from which it flows, at a very high speed, into the mixing chamber 12. The high speed generates a vacuum pressure in the mixing chamber 12, which in turn draws the abrasive material in suspension 21 from the tank 22 through the abrasive inlet channel 23. The abrasive material in suspension 21 and the water jet are then mixed in the mixing chamber 12 and, subsequently, conveyed into the focusing tube 14 from which a jet 15 of water and abrasive material is delivered.

[0086] A suitable cutting head is, for example, the model Dialine manufactured and marketed by Hyperterm Inc. or the model Slice Two manufactured and marketed by Diamond Technology Innovations.

[0087] Advantageously, according to the invention, this nozzle is equipped with a focusing tube of the jet with a length preferably between 100 mm and 200 mm and more preferably between 140 mm and 160 mm. The nozzle thus configured creates a jet of water and abrasive material capable of remaining cohesive for a greater distance relative to that of a conventional AWJ system, allowing a greater depth of this jet with the same material processed.

[0088] According to a preferred variant, said focusing tube comprises two portions of tube joined together by a removable connection means (not illustrated). In this way, it is possible to use, as portions, focusing tubes of smaller standard length, which are more widely available and less costly. Moreover, as the portion closest to the outlet of the jet is subject to greater wear, said portions can be disassembled and reversed after a given period of operation, thereby advantageously extending the life of the focusing tube before replacement.

[0089] Suitable focusing tubes are, for example, the models Roctec 100 or Roctec 500, manufactured and marketed by Kennametal Inc.

[0090] To regulate the amount of abrasive material in suspension 21 introduced into the mixing chamber 12, the apparatus is equipped with flow regulating means 27. Said flow regulating means 27 preferably comprise a moving partition positioned on the abrasive inlet channel 23 or, preferably, directly on the abrasive outlet on the tank 22.

[0091] The moving partition, by widening or narrowing the section of the opening for the flow of abrasive material to pass through, regulates the flow of this material conveyed toward the mixing chamber as a result of the vacuum pressure.

[0092] The moving partition can be moved either manually or by means of an electric or pneumatic actuator associated therewith.

[0093] In a preferred variant of the invention, the apparatus is equipped with a mixing device 24 provided with agitator means to mix the abrasive particles and the liquid or gelatinous substance to form the abrasive material in suspension 21. Advantageously, said mixing device 24 is in communication with the tank 22.

[0094] A pump 25, if provided, can directly feed the abrasive material in suspension into said tank.

[0095] According to another mode of embodiment of the invention, the apparatus comprises dosing means 26 associated with said mixing device 24 to dose at least the water, the gelling agent and, optionally, the particles of abrasive material to form the abrasive material in suspension.

[0096] Preferably, the gelatinous substance is prepared by mixing water and the gelling agent, this latter being between 0.05% and 5% of the volume of the water used, and more preferably around 3%.

[0097] According to another variant of the invention, the apparatus is equipped with a recovery and recycling system of the abrasive material, indicated as a whole with the reference number 30.

[0098] According to the invention, this recycling system comprises a recovery device 32 configured to receive a wet mass of abrasive particles and of waste material from a collection container 31, positioned in an area below the nozzle. The process water and the abrasive material of the jet 15, as well as the waste material from processing, are collected in this container 31. A suitable recovery device is, for example, described in U.S. Pat. No. 6,299,510 B1.

[0099] According to the invention, the recycling system 30 also comprises separation means 33, adapted to separate the wet mass of reusable abrasive particles from the wet mass of non-reusable abrasive particles and from the waste material.

[0100] In particular, these separation means 33 are configured to separate particles with a size greater than a given value, comprising processing waste from the workpiece, and particles with a size below a given threshold, comprising both processing waste and crushed particles of abrasive. These products are conveyed into a waste container 36 to be disposed of correctly.

[0101] Typically, the separation means 33 comprise a cyclone device 34, if necessary associated with a filter device 35.

[0102] These devices are well known to those skilled in the art and therefore will not be described in more detail.

[0103] The wet mass of reusable abrasive particles can then be stored in a collection tank 37 or, preferably, conveyed toward the source of the abrasive material in suspension 20, for example by means of an auger or equivalent pumping means.

[0104] Advantageously, this wet mass of reusable abrasive particles can be conveyed directly into the mixing device 24 for the production of other abrasive material in suspension to be used in the machining process.

[0105] According to this variant, further dosing means are preferably provided to control the amount of recycled abrasive material introduced into the mixing device 24.

[0106] Therefore, also in this case the apparatus guarantees that the abrasive material in suspension prepared has the correct percentage of dispersed abrasive particles. Moreover, with this system it is also possible, if necessary, to introduce new dry abrasive particles into the mixer and to dose their amount relative to the amount of recovered wet particles.

[0107] With the recycling system thus configured it is possible to recycle between 30% and 70% of the abrasive material used, as a function of the hardness of the material and of the thickness of the machined workpiece.

[0108] Due to the re-introduction of the wet mass of reusable abrasive particles, the recycling system is particularly advantageous from the point of view of operating costs, making recovery and recycling profitable also for users of apparatus for water jet cutting.

[0109] Said recovery operations of the abrasive material can be implemented continuously during operation of the cutting apparatus. If the amount of abrasive particles recovered is not sufficient to guarantee the correct flow of abrasive material in suspension, new dry particles can be mixed with the recovered wet particles, the water and the gelling agent.

[0110] The invention has been described purely for illustrative and non-limiting purposes, according to some preferred embodiments. Those skilled in the art may find numerous other embodiments and variants, all falling within the scope of protection of the claims below.