FOCUSING TUBE, AND USE THEREOF

Abstract

A focusing tube is configured to focus a high-pressure liquid jet containing abrasive particles. The focusing tube has a focusing duct portion and an exit opening for the free discharge of the liquid jet from the focusing duct portion. A center point of the discharge opening coincides with the longitudinal axis of the focusing duct portion. The focusing duct portion is delimited by a liquid-impermeable channel wall, extends from the discharge opening at a focusing taper angle and is tapered toward the discharge opening. The focusing taper angle lies in a range from 0.05° to 1°. This allows the service life of the focusing tube to be increased in a way that is simple in terms of design.

Claims

1-15. (canceled)

16. A focusing tube configured for focusing a highly pressurized liquid jet that contains abrasive particles, the focusing tube comprising: a focusing duct portion having a longitudinal axis; an exit opening for the liquid jet to freely exit said focusing duct portion, said exit opening having a center lying on said longitudinal axis of said focusing duct portion; said focusing duct portion being delimited by a liquid-impermeable duct wall tapering at a focusing taper angle in a direction toward said exit opening; said focusing taper angle lying in a range from 0.05° to 1 °; and said focusing taper angle being defined by legs being two tangents lying in a longitudinal sectional plane that contains the longitudinal axis of said focusing duct portion and bearing on two internal surface points of said duct wall that lie opposite one another and in the longitudinal sectional plane.

17. The focusing tube according to claim 16, wherein said focusing taper angle lies in a range from 0.1° to 0.8°.

18. The focusing tube according to claim 16, wherein said focusing duct portion, in terms of the longitudinal axis, in a cross section relating to the longitudinal axis, has a maximum diameter of 0.5 mm to 5 mm at each axial position thereof.

19. The focusing tube according to claim 16, wherein said focusing duct portion is rotationally symmetrical about the longitudinal axis.

20. The focusing tube according to claim 16, wherein said focusing duct portion is frustoconical.

21. The focusing tube according to claim 16, wherein said focusing duct portion, measured parallel to the longitudinal axis of said focusing duct portion, extends over at least 50% of a length of the focusing tube.

22. The focusing tube according to claim 21, wherein said focusing duct portion extends over at least 70% of the length of the focusing tube.

23. The focusing tube according to claim 16, wherein: the focusing tube is formed with an inlet duct portion extending from an entry opening for the liquid jet to enter into the focusing tube to a transfer opening that is formed conjointly with said focusing duct portion; said inlet duct portion has a longitudinal axis containing a center of said entry opening; and outside the transfer opening, in terms of the longitudinal axis of the inlet duct portion in a cross section relating to the longitudinal axis of the inlet duct portion, has a maximum diameter at each axial position which is greater than a maximum diameter of said focusing duct portion.

24. The focusing tube according to claim 23, wherein the longitudinal axis of said focusing duct portion and the longitudinal axis of said inlet duct portion are coaxial with one another.

25. The focusing tube according to claim 23, wherein: said inlet duct portion is delimited by said liquid-impermeable duct wall, tapers in a direction of said transfer opening, and extends at an inlet taper angle; said inlet taper angle having legs being two tangents that lie in a longitudinal sectional plane containing the longitudinal axis of said inlet duct portion and bear on two internal surface points of said duct wall that lie opposite one another in said longitudinal sectional plane; and said inlet taper angle outside said transfer opening is greater than said focusing taper angle.

26. The focusing tube according to claim 25, wherein said inlet taper angle lies in a range from 10° to 90°.

27. The focusing tube according to claim 25, wherein said inlet taper angle lies in a range from 27° to 37°.

28. The focusing tube according to claim 23, wherein said inlet duct portion transitions in a stepless manner to said transfer opening.

29. The focusing tube according to claim 23, wherein a length of said focusing duct portion, measured parallel to the longitudinal axis of said focusing duct portion, is greater than a length of said inlet duct portion, measured parallel to the longitudinal axis of said inlet duct portion, by a factor of at least five.

30. A method of cutting a workpiece, the method which comprises providing a focusing tube according to claim 16, conducting a pressurized flow of liquid containing abrasive particles through the focusing tube and jetting the liquid containing the abrasive in a liquid jet at the workpiece for cutting the workpiece.

Description

[0039] Further advantages and expedient features of the invention are derived from the description hereunder of exemplary embodiments with reference to the appended figures, in which:

[0040] FIG. 1: shows a schematic longitudinal sectional illustration of a focusing tube according to a first embodiment;

[0041] FIG. 2: shows an end-side view of the focusing tube from FIG. 1;

[0042] FIG. 3: shows a perspective schematic illustration of a focusing tube according to a second embodiment;

[0043] FIG. 4: shows a schematic interrupted longitudinal sectional illustration of the focusing tube from FIG. 3;

[0044] FIG. 5: shows an enlargement of a detail of the longitudinal sectional illustration from FIG. 4; and

[0045] FIG. 6: shows a diagram in which the wear on a focusing tube in the context of the present disclosure and the wear on a focusing tube used as reference are in each case plotted as a function of the operating life.

[0046] FIG. 1 and FIG. 2 schematically show a focusing tube 1 according to a first embodiment. It becomes evident by means of the longitudinal sectional illustration from FIG. 1 how the focusing taper angle is to be determined in the context of the present disclosure.

[0047] The focusing taper angle 2 has two legs which in FIG. 1 are provided with the reference signs 3 and 4. The focusing taper angle 2 is in the range from 0.05° to 1° and in FIG. 1 has been plotted so as to be larger merely for reasons of clarity. The legs 3 and 4 lie in a longitudinal sectional plane 5 which coincides with the drawing plane of FIG. 1. The longitudinal sectional plane 5 contains a longitudinal axis 6. The longitudinal axis 6 contains a centre 7 of an exit opening 8, as can be seen when FIG. 1 and FIG. 2 are viewed in combination. Since the exit opening 8 is circular, the centre 7 is the centre of a corresponding circle. The longitudinal axis 6 extends in the direction of a focusing duct portion 9 which is delimited by a duct wall 11 and extends from the exit opening 8 into the interior of the focusing tube 1, as is shown in FIG. 1. The focusing duct portion 9 tapers in the direction of the exit opening 8 such that a water jet, which contains abrasive particles and is highly pressurized to at least 1000 bar when flowing through the focusing duct portion 9 in the direction of the exit opening 8, is focused to the diameter of the exit opening 8 and, focused in such a manner, freely exits the exit opening 8.

[0048] The longitudinal sectional plane 5 moreover contains two points 3a and 4a which are to be assigned to an internal surface 10 of the duct wall 11 and, in the longitudinal sectional plane 5, are connected by a straight line 12 which is perpendicular to the longitudinal axis 6. The legs 3 and 4 are tangents which bear on the points 3a and 4a.

[0049] When FIG. 1 and FIG. 2 are viewed in combination, it becomes evident that the focusing duct portion 9 is configured so as to be circular-frustoconical. The intersecting lines associated with the internal surface 10 are therefore straight and coincide with the legs or tangents 3 and 4, respectively. It is however also conceivable and possible for the focusing duct portion 9 to have another shape such that the intersection lines would be curved inward in a convex manner, for example.

[0050] FIGS. 3 to 5 show a focusing tube 1′ according to a second embodiment. The focusing tube 1′ is constructed in a manner analogous to that of the focusing tube 1. The focusing tube 1′ thus has a focusing duct portion 9′ which, so as to be parallel to a longitudinal axis 6′, extends from an exit opening 8′ into the interior of the focusing tube 1′, tapers in the direction of the exit opening 8′, and is delimited by a duct wall 11′. The duct wall 11′ is composed of a sintered hard metal (cemented carbide). The duct wall 11′ is therefore liquid-impermeable.

[0051] The longitudinal axis 6′ contains the centre 8a′ of the exit opening 8′. The longitudinal axis 6′ and thus the centre 8′ are contained in a longitudinal sectional plane 5′ which, in relation to the longitudinal sectional plane 5, is positioned in a manner analogous to that described in the context of FIGS. 1 and 2.

[0052] In comparison to the focusing tube 1, the focusing tube 1′ additionally has an inlet duct portion 13′ which from an exit opening 14′ extends into the interior of the focusing tube 1′ and tapers in the direction of a transfer opening 15′. The transfer opening 15′ is an inner opening of the focusing tube 1′ that is formed conjointly with the focusing duct portion 9′. The transfer opening 15′ can be referred to as an exit opening 15′ of the entry duct portion 13′ and at the same time as an entry opening 15′ of the focusing duct portion 9′. When a water jet. which contains abrasive particles and is highly pressurized to at least 1000 bar, from a mixing chamber in which the abrasive particles are mixed with the water jet, enters the entry opening 14′, the flow of the water jet passes through the entry duct portion 13′. Because the entry duct portion 13′ tapers in the direction of the transfer opening 15′, and the entry duct portion 13′ outside the transfer opening 15′ has a larger internal diameter than the focusing duct portion 9′, the flow of the water jet is pacified and the water jet is pre-focused. Once the water jet has entered the focusing duct portion 9′ through the transfer opening 15′, the water jet in the focusing duct portion 9′ is focused to the diameter of the exit opening 8′. This focusing has the effect that the water jet and thus the abrasive particles are accelerated to an exit speed of at least 400 m/s in terms of exiting the exit opening 8′.

[0053] It can be particularly readily seen from FIG. 4 that the focusing duct portion 9′ has a focusing taper angle 2′. The focusing taper angle 2′ in an exemplary manner is 0.18°. However, other focusing taper angles 2′ from the range from 0.05° to 1° are also conceivable and possible. The focusing taper angle 2′ has two legs 3′ and 4′. The legs 3′ and 4′ are tangents which lie in the longitudinal sectional plane 5′. The two legs 3′ and 4′, or the tangents 3 and 4′, respectively, bear on two points 3a′ and 4a′ of an internal surface 10′ of the duct wall 11′ that lie opposite one another in the longitudinal sectional plane 5′. The focusing taper angle 2′ is constant because the focusing duct portion 9′ is configured so as to be circular-frustoconical and rotationally symmetrical about the longitudinal axis 6′.

[0054] The inlet duct portion 13′ has an inlet taper angle 16′ that is defined in a manner analogous to the focusing taper angles 2 and 2′. The inlet taper angle 16′ thus has two legs 17′ and 18′ which lie in the longitudinal sectional plane 5′, because the focusing duct portion 9′ and the inlet duct portion 13′ are disposed so as to be mutually coaxial. The legs 17′ and 18′, or the tangents 17′ and 18′, respectively, bear on two points 17a′ and 18a′ of an internal surface 19′ of the duct wall 11′ that lie opposite one another in the longitudinal sectional plane 5′. The inlet duct portion 13′ has a longitudinal axis 6′ which coincides with the longitudinal axis 6′ of the focusing duct portion 9′. The longitudinal axis 6 of the inlet duct portion 13′, or of the focusing duct portion 9′, respectively, contains the centre 20′ of the circular entry opening 14′. The inlet taper angle is 35°. However, other inlet taper angles from the range from 10° to 90° are also conceivable and possible.

[0055] The diagram from FIG. 6 shows the diameter enlargement in percentage, referred to as r herein, of an exit opening of a focusing tube Exp. and of a focusing tube Ref. used as a reference, in each case as a function of the operating hours h. Both the focusing tube Exp. and the focusing tube Ref. in the region of the focusing duct portion thereof have been passed through by a flow of a water jet containing abrasive particles at 6000 bar at constant jet parameters. In the case of the focusing tube Exp. the focusing tube portion, in a manner analogous to that of the focusing duct portion 9′, was configured so as to taper in the direction of the exit opening at a focusing taper angle of 0.18°. In the case of the focusing tube Ref. however, the focusing duct portion had a constant internal diameter, thus no taper in the direction of the exit opening. With this exception, the focusing tubes Exp. and Ref. do not differ from one another. It can be seen from FIG. 6 that the focusing taper angle of 0.18°, chosen in an exemplary manner for the range from 0.05° to 1°, ensures that the wear on the focusing tube Exp. after an operating life of 40 h is already significantly less than the wear on the focusing tube Ref. The diameter of the exit opening of the focusing tube Exp. has thus increased by approximately 16% after 100 operating hours, whereas the diameter of the exit opening of the focusing tube Ref. has increased by approximately 26% after 100 operating hours.