Nozzle system, powder blasting device and method for using a nozzle system

Abstract

Nozzle system for a powder blasting device including a first nozzle element for transporting a powder-gas mixture stream along a transporting direction and a second nozzle element, where the second nozzle element surrounds the first nozzle element such that at least one channel is formed between the first nozzle element and the second nozzle element, where the channel is provided for transporting a liquid stream, where the first nozzle element and the second nozzle element are arranged such that in operation the powder-gas-mixture stream ejected by the first nozzle element is encased by the liquid stream ejected by the channel for forming an output stream of the nozzle system, where the first nozzle element has an acceleration part having a first cross section and a spreading part having a second cross section, where the spreading part is arranged downstream of the acceleration part.

Claims

1. Nozzle system for a powder blasting device comprising a first nozzle element for transporting a powder-gas mixture stream along a transporting direction and a second nozzle element, wherein the second nozzle element surrounds the first nozzle element such that at least one channel is formed between the first nozzle element and the second nozzle element, wherein the channel is provided for transporting a liquid stream, wherein the first nozzle element and the second nozzle element are arranged such that in operation the powder-gas-mixture stream ejected by the first nozzle element is encased by the liquid stream ejected by the channel for forming an output stream of the nozzle system, wherein the first nozzle element has an acceleration part having a first cross section and a spreading part having a second cross section, wherein the spreading part is arranged downstream of the acceleration part, characterized in that the second cross section is larger than the first cross section.

2. Nozzle system according to claim 1, wherein the acceleration part has a first cross section being constant in a direction extending along the transporting direction and/or the spreading part has a second cross section being at least partially constant in a direction extending along the transporting direction.

3. Nozzle system according to claim 1, wherein the first cross section has a first width measured perpendicular to the transporting direction and a second cross section has a second width measured perpendicular to the transporting direction, wherein the second width is up to three times larger than the first width and/or wherein the first width has a width between 0.1 and 2.5 mm.

4. Nozzle system according to claim 1, wherein the first nozzle element comprises a collecting part, wherein the collecting part is arranged upstream to the acceleration part, wherein the collecting part has a third cross section being preferably at least partially constant along the transporting direction.

5. Nozzle system according to claim 4, wherein the third cross section is larger than the first cross section, wherein a third width of the third cross section is up to three times larger than the first width, wherein the first width has a width between 0.1 and 2.5 mm.

6. Nozzle system according to claim 1, wherein an inner curvature of the first nozzle element in a transition area or in the spreading part has a step-like and/or a cone-like shape.

7. Nozzle system according to claim 1, wherein the acceleration part has a first length measured along the transporting direction and the spreading part has a second length measured along the transporting direction, wherein the second length is 0.5 to 3.5 times longer than the first length.

8. Nozzle system according to claim 1, wherein the liquid stream is ejected from the channel via an output surface, wherein the channel is configured such that the liquid stream encasing the powder-gas mixture stream is formed by droplets.

9. Nozzle system according to claim 8, wherein the output surface has a fourth cross section, wherein the fourth cross section has a size between 0.1 and 0.9 mm.sup.2.

10. A nozzle system for a powder blasting device, comprising a first nozzle element for transporting a powder-gas mixture stream along a transporting direction and a second nozzle element, wherein the second nozzle element surrounds the first nozzle element such that at least one channel is formed between the first nozzle element and the second nozzle element, wherein the channel is provided for transporting a liquid stream, wherein the first nozzle element and the second nozzle element are arranged such that in operation the powder-gas-mixture stream ejected by the first nozzle element is encased by the liquid stream ejected by the channel via an output surface for forming an output stream of the nozzle system, wherein the output surface has a fourth cross section, wherein the fourth cross section has a size between 0.3 and 0.4 mm.sup.2.

11. Nozzle system according to claims 8 to 10, wherein the fourth cross section is formed as a slit, an assembly of holes and/or assembly of grooves.

12. Nozzle system according to claim 10, wherein an outer curvature of the first nozzle elements defines the shape of the fourth cross section, wherein the outer curvature of the first nozzle element comprises at least one recess being curved inwardly.

13. Nozzle system according to claim 10, wherein in a direction parallel to the transporting direction the first nozzle element extends further than the second nozzle element or the first nozzle element and/or the second nozzle element ends at a common plane being perpendicular to the transporting direction.

14. Powder blasting device comprising the nozzle system according to claim 1.

15. Method for using a nozzle system according to claim 1 in a powder blasting device.

16. Method according to claim 15, wherein the output stream has a fifth cross section that differs from a circularly formed cross section

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the drawings:

[0035] FIG. 1 schematically shows a nozzle system according to a preferred embodiment of the present disclosure,

[0036] FIG. 2 schematically shows a first nozzle element according to the state of the art

[0037] FIG. 2a to 2d schematically show different preferred embodiments of a first nozzle element for a nozzle system according to the present disclosure

[0038] FIG. 3 schematically shows a perspective view on a front end of a nozzle system according to the state of the art

[0039] FIGS. 3a to 3i schematically show different preferred embodiments for nozzles systems according to the present disclosure in a perspective view directed on the front end of the nozzle system and

[0040] FIG. 4 a fifth cross section assigned to the output stream.

DETAILED DESCRIPTION

[0041] In FIG. 1 a nozzle system 1 according to a preferred embodiment of the present disclosure is presented in a sectional side view along a transporting direction T. Such nozzle systems 1 are preferably an essential part of a powder blasting device. Those power blasting devices are preferably used for removing stains, tartar or a coloration from a tooth and/or for removing dental biofilms. The nozzle system 1 provides an output stream 2 that is able to remove stains and coloration and/or to remove dental biofilms. In operation, the output stream 2 is ejected by the nozzle system 1 at its front end FE.

[0042] Besides a powder-gas mixture stream 21 the output stream 2 comprises a liquid stream 22 in order to guide the powder-gas mixture stream 21 and to trap dust generated and to avoid mist during operation. In particular, the powder-gas mixture stream 21 is encased or surrounded at least partially, preferably completely, by the liquid stream 22 in a plane expanding perpendicular to a transporting direction T of the output stream 2. For realizing such an output stream 2 the nozzle system 1 comprises a first nozzle element 10 for transporting a powder-gas mixture stream 21 along the transporting direction T and a second nozzle element 20, wherein the second nozzle element 20 surrounds the first nozzle element 10 such that at least one channel 25 is formed between the first nozzle element 10 and the second nozzle element 20. Preferably, the first nozzle element 10 and/or the second nozzle element 20 have a sleeve—like body, wherein the first nozzle element 10 is arranged inside the second nozzle 20 element, in particular concentrically to each other. Preferably, the output stream 2 is ejected from the nozzle system 1 at a front end FE or a front side of the nozzle system 2. Preferably, the first nozzle element 10 extends further than the second nozzle element 20 in a direction extending parallel to the transporting direction T. Alternatively, the first nozzle element 10 and the second nozzle element 20 end in a common plane that extends perpendicular to the transporting direction T.

[0043] For improving a quality of the output stream 2, in particular regarding a reduced abrasivity in operation, it is provided to adapt a geometry of the first nozzle element 10. In particular, the first nozzle element 10 has an acceleration part 11 having a first cross section and a spreading part 12 having a second cross section, wherein the spreading part 12 is arranged downstream of the acceleration part 11. Thereby, the particles of the powder-gas mixture stream 21 are accelerated inside the acceleration part 11 and thus gain speed during their transport inside the acceleration part 11. The spreading part 12 is configured such that the particles of the powder-gas mixture stream 21 are spread. For realizing the spreading inside the spreading part 21 it is preferably provided that the second cross section is larger than the first cross section. In particular the acceleration part 11 is arranged directly next to the spreading part 12 in a direction extending parallel to the transporting direction T.

[0044] In particular, it is provided the first cross section has a first width W1 measured perpendicular to the transporting direction T and a second cross section has a second width W2 measured perpendicular to the transporting direction T, wherein the second width W2 is up to three times, preferably up to 2.5 times and most preferably up to 2 times, in particular mainly 1.5 times, larger than the first width W1 and/or wherein the first width W1 has a width between 0.2 and 1.5 mm, preferably between 0.4 and 0.9 mm and most preferably 0.6 mm. By enlarging the cross section, in particular by using the mentioned dimensions of the first width W1 and the second width W2, it is advantageously possible to reduce the abrasivity of the output stream 2. Further, a sound shock is generated inside the nozzle system 1 and not at the front end of the nozzle system 1. As a consequence, noises generated by the nozzle system 1 during operation can be reduced for giving an operator and/or patient a more comfortable impression. Additionally, it is possible to enlarge an absolute output cross section of the powder-gas mixture stream 12 being ejected by the first nozzle element 10 without increasing an air flow rate. As a consequence of the enlarged output cross section of the powder-gas mixture stream 21, an emphysema risk is reduced and a wider range of properties regarding the output stream 2 can be established, for example a thinner or larger output stream measured in a direction perpendicular to the transporting direction T.

[0045] Further, it is provided that in a direction extending parallel to the transporting direction T a curvature/inner side 14 of the first nozzle element 10 has a step-like shape for forming a transition between the acceleration part 11 and the spreading part 12. Furthermore, it is provided that the acceleration part 12 is arranged concentrically to the spreading part 12. Thus, a homogeneous spreading can be guaranteed.

[0046] Furthermore, the first nozzle element 10 comprises a collecting part 13, wherein the collecting part 13 is arranged upstream to the acceleration part 11, wherein the collecting part has a third cross section being preferably constant along the transporting direction T. By using the collecting part 13 it is advantageously possible to prepare particles for entering the acceleration part 11 properly. The third cross section might correspond to the second cross section of the spreading part 12 or might be different form the second cross section, for example regarding size and steps, i.e. a form of the inner side 14 of the first nozzle element 10. In particular, the inner curvature/side 14 of the first nozzle element 10 has another step-like shape forming the transition from the collecting part 13 to the acceleration part 11. It is also conceivable the transition between the collecting part 13 and the acceleration part 11 is funnel shaped. In particular, the third cross section is larger than the first cross section, wherein a third width W3 of the third cross section is up to three times, preferably up to two times and most preferably up to 1.6, in particular mainly 1.2 times, larger than the first width, wherein the first width has a width between 0.2 and 1.5 mm, preferably between 0.4 and 0.9 mm and most preferably mainly 0.6 mm.

[0047] Moreover, the acceleration part 11 has a first length L1 measured along the transporting direction T and the spreading part 12 has a second length L2 measured along the transporting direction T, wherein the second length L2 is 0.5 to 3.5 times, preferably 1.1 to 2 times and most preferably 1.3 to 1.8 times, longer than the first length L1. In particular, the first length L1 should be longer than 0.5 mm.

[0048] Furthermore, it is provided that the channel 25 is configured such that a small/thin liquid jet is generated for the output stream 2. In particular, an output surface 23 from which the liquid jet is ejected preferably has comparable small fourth cross section. Preferably, the fourth cross section is measured in a plane extending perpendicular to the transporting direction T at the front end FE. Hereby, all openings used and/or being available for ejecting the liquid stream preferably form the fourth cross section, i.e. the fourth cross section might be formed by sub-cross sections assigned to several separated or individual openings at the front end for ejecting the liquid stream 22. In particular, the fourth cross section has a structure or profile formed by a plurality of openings that for example are arranged circumferential at the front end FE of the channel 25, preferably uniformly along a circle. In particular, the fourth cross section preferably has a size between 0.1 and 0.8 mm.sup.2, preferably between 0.6 and 0.3 mm.sup.2 and most preferably between 0.3 and 0.4 mm.sup.2. In contrast to that, the forth cross section according to the state of the art is larger than 0.8 mm.sup.2.

[0049] In particular, the fourth cross section is preferably configured such that the liquid stream 22 encasing the powder-gas mixture stream 12 is formed by droplets. Due to the use of droplets it is advantageously possible to increase a probability of the liquid to trap dust powder. Furthermore, a controlled liquid stream 22 supports directing or guiding of the powder—gas mixture stream 21.

[0050] Such geometry of the channel 25 allows by itself to reduce the abrasivity of the output stream. Therefore, a nozzle system (1) for a powder blasting device is provided, comprising

[0051] a first nozzle element (10) for transporting a powder-gas mixture stream (21) along a transporting direction (T) and

[0052] a second nozzle element (20), wherein the second nozzle element (20) surrounds the first nozzle element (10) such that at least one channel (25) is formed between the first nozzle element (10) and the second nozzle element (20), wherein the channel (25) is provided for transporting a liquid stream (22), wherein the first nozzle element (10) and the second nozzle element (20) are arranged such that in operation the powder-gas-mixture stream (21) ejected by the first nozzle element (10) is encased by the liquid stream (22) ejected by the channel (25)) via an output surface (23) for forming an output stream (2) of the nozzle system (1), wherein the output surface (23) has a fourth cross section, wherein the fourth cross section has a size between 0.3 and 0.4 mm.sup.2 for reducing abrasivity of the output stream.

[0053] In FIG. 2 a first nozzle element 10 according to the prior art is presented for comparing it to the geometries of the first nozzle elements 10 of the FIGS. 2a to 2d representing different exemplary embodiments of first nozzle elements 10 for a nozzle system 1 according to the present disclosure. In particular, FIG. 2a shows a first nozzle element 10, assigned to a nozzle system 1 being named EA-5698 in the following, which has no collecting part. Further, the first nozzle element 10 has a comparable long acceleration part 11 compared to the spreading part 12. The elements 17, such as struts or rips, extending at an outer side 15 of the first nozzle element 10 are intended for realizing sub-channel and a structured output surface 23 of the channel 25 ejecting the liquid stream 22. Preferably, the struts and/or rips have a length longer than the second length L2. Moreover, the second width W2 is about 0.8 mm, whereas the inner diameter of the first nozzle element 10 according to the prior art is about 0.65 mm. The first nozzle element 1 in FIG. 2b has a collecting area 13 and refers to a nozzle system 1 named EA 5682 in the following. Its second width W2 is about 0.7 mm. The first length L1 is about 3 to 5 mm and the second length L2 about 2 to 3 mm. A third length L3 assigned to the collecting part 13 is about 0.3 to 0.7 mm and the third width is about 1 mm. Furthermore, it is provided that the transition between the collecting part 13 and the acceleration part 11 is funnel shaped. Moreover, the third width W3 being for example about 1 mm is larger than the second with being for example about 0.7 mm. The first width is about 0.61 mm.

[0054] The first nozzle element 10 of FIG. 2c is for example part of a nozzle system 1 assigned to the name EA-5701. The first nozzle element 10 of FIG. 2c differs from that of FIG. 2b by the design of the inner curvature/side 14 of the spreading part 12, wherein the inner curvature/side along the transporting direction T has a step like shape. In the illustrated embodiment, several subsection, in particular three subsection 25, are provided, wherein the sub-sections 25 have the same length measured along the transporting direction T. For example, the length of each subsection is about 1.5 mm, consequently forming a second length L2 of about 4.5 mm. Furthermore, it is preferably provided that a respective second width W2 assigned to each of the subsection increases along the transporting direction T. For example the second width W2 is increased by 0.2 mm by each transition from one subsection 26 to the next subsection 26 in transporting direction T. Alternatively, it is also convincible that the enlargement of the second width W2 between adjacent subsections 26 and/or the length of each subsection 26 differs along the transporting direction T.

[0055] In FIG. 2d a further first nozzle element 10 is presented and this first nozzle element is part of the nozzle system called EA-5697 in the following. Compared to the embodiment of FIG. 2b, a longer collecting part 13 is provided. Furthermore, it is provided that the third width W3 being for example about 0.8 mm is smaller than the second with W2 being for example about 1 mm.

[0056] In FIG. 3 a front end FE of a nozzle system 1 according to the prior at is presented in a perspective view for comparing it to front ends FE of nozzle systems 1 of the FIGS. 3a to 3i representing different exemplary embodiments of nozzle system 1 according to the present disclosure. In particular, the view at the front end FE shows the fourth cross section formed at the end of the channel 25 for ejecting the liquid stream 22. The nozzle system 1 representing the prior art is called in the following EMS. This nozzle system 1 is ringshaped and has no structures included in the channel 25 for forming a profiled fourth cross section. In contrast to that, the channel 25 of the nozzle systems 2 illustrated by the FIGS. 3a to 3h is formed by several sub-channels, in particular groove like sub-channels, between the first nozzle element 10 and the second nozzle element 20. The sub-channels extends preferably parallel to the transporting direction T and their ends at the front end of the nozzle system 1 forms the fourth cross section. In particular, the sub-channels have a fourth length L4 measured in a direction extending parallel to the transporting direction T. Preferably, the fourth length L4 is determined by the length of rip elements and/or strut elements 17 protruding from the first nozzle element 10 radially. For example, the fourth length L4 is longer than the second length L2. In particular, a ratio of the second length L2 to the fourth length L4 is larger than 1, preferably larger than 2 and most preferably larger than 3.

[0057] In particular, the struts elements 17 are part of the first nozzle element 10. Moreover, it is provided that the outer surface/side 15 of the first nozzle element 10 has an arched shape between two adjacent strut elements 17. In particular the first nozzle element 10 includes grooves 35 for forming the sub-channels. Thereby the outer surface/side 15 of the first nozzle element 10 is shaped/curved inwardly. In the nozzle systems of the FIGS. 3a to 3d the arched shape is mainly parabolic and six different sub-channels are formed by six radially extending strut elements 17. The nozzle system of the FIGS. 3a to 3d mainly differs from each other by the thickness of a wall assigned to the first nozzle element 10.

[0058] In the FIGS. 3e and 3f more than six sub-channels are realized. In the FIGS. 3f and 3g are less than six sub-channels formed and the arched shape is mainly like a circular arc. In FIG. 3i the fourth cross section is formed by a slit 36.

[0059] Furthermore, the nozzle system of FIG. 3a refers to EA 5682, the nozzle system of FIG. 3b to EA 5701, the nozzle system of FIG. 3c to EA 5698 and the nozzle system of FIG. 3d to EA 5697. For those nozzle systems an abrasivity of the output stream 1 was measured and compared to the abrasivity of the nozzle system named EMS. Abrasivity test is carried out by using a test bench where the nozzle is placed at 45° and 2 mm of projected distance. A shutter in front of the nozzle is used to determine the exposure time. To determine the abrasivity, the test material is a PMMA plate. 16 abrasion points are made for each test using the same application time. In order to avoid experimental bias, the exposure time is adjusted to get abrasion holes of 20 to 200 microns. The exposure time is mostly between 1 and 5 seconds. This exposure time is not a key parameter as the outcome is normalized according to the powder amount used. Therefore the abrasivity is defined as the crater depth generation rate over powder quantity. Abrasivity=Crater depth [μm]/powder quantity used [g]

[0060] The abrasivity of EMS had a value between 1700 and 2333 μm/g, EA-5682 had a value between 1300 and 1600 μm/gm, EA-5701 had a value between 900 and 1100 μm/g, EA-5698 had a value between 700 and 1100 μm/g and ES 5697 had a value between 400 and 600 μm/g.

[0061] In FIG. 4 a fifth cross section Q5 assigned to the output stream realized by EA-5701 is shown. The fifth cross section of the output stream is visualized by directing the output stream 2 on a painted steel surface located at a distance of 2.2 mm from the front end FE of the nozzle system 1. It can be seen that the fifth cross section differs from a circularly formed cross section.