Field nozzle

Abstract

Pelton nozzle with a nozzle needle (1) which can be moved along an axis, a nozzle tip (2) and an insert ring (3) which is connected to the nozzle tip (2) and which surrounds the axis, wherein the connection between the nozzle tip (2) and the insert ring (3) is designed as a bayonet fitting, and wherein the nozzle tip (2) surrounds the insert ring (3) in the installed position over more than half the axial length L of the insert ring (3) with respect to the axis.

Description

[0001] The invention relates to a Pelton nozzle with an insert ring. Insert rings in Pelton nozzles are replaceable wear parts that are connected to the nozzle nozzle. According to the invention, the insert ring is connected to the nozzle nozzle via a type of bayonet lock.

[0002] Bayonet locks are well-known and have a wide range of technical applications. This type of connection is relatively rare in hydropower plants. For example, they are used to connect hoses in the auxiliary systems of hydropower plants. A somewhat more distinct prior art is CN 1 03 375 398 A, in which a bayonet lock is arranged at the water outlet of a submersible electric pump. This, too, is essentially a hose connection. The closest prior art is WO 2015 / 036 212 A1, which discloses a generic Pelton nozzle in which the tip cone of the nozzle needle is attached with a bayonet lock.

[0003] Traditionally, the insert rings of Pelton nozzles are connected to the nozzle mouthpiece by screws. EP 2 035 690 B1, for example, discloses Fig. 1 such a conventional Pelton nozzle. However, in this document, the component referred to as the “insert ring” is referred to as the “nozzle mouthpiece (wear ring)” (see Fig. 1 and the parts list on page 6). As described in more detail below, the screws connecting the insert ring to the nozzle tip are subject to bending stress during operation of the Pelton nozzle, which significantly shortens the service life of the screws. Breaking the screws would pose a safety risk, as in addition to causing mechanical damage, it would no longer be possible to shut down the machine using the nozzle needles.

[0004] CH 632 056 A5 discloses a generic Pelton nozzle with a nozzle mouthpiece and an insert ring, wherein the nozzle mouthpiece encloses the insert ring in the installed position over more than half the axial length of the insert ring with respect to the axis.

[0005] The object of the invention is to provide a Pelton nozzle in which the described safety risk can no longer occur.

[0006] The object is achieved according to the invention by an embodiment according to the independent main claim 1. An advantageous embodiment of the present invention can be found in the sole subclaim 2.

[0007] The invention is explained below with reference to the figures. The figures show in detail: Fig. 1: Pelton nozzle according to the state of the art Fig. 2: Pelton nozzle according to the invention in a first embodiment Fig. 3: Pelton nozzle according to the invention in a further embodiment

[0008] Fig. 1 shows a Pelton nozzle according to the prior art. Fig. Figure 1 shows only the nozzle tip area in a schematic representation. The Pelton nozzle comprises a nozzle needle, designated 1, which can be moved along an axis, a nozzle nozzle, designated 2, and an insert ring, designated 3. The insert ring 3 is connected to the nozzle nozzle 2 by screws and wraps around the axis of the nozzle needle 1. Fig. 1, the axis is indicated by the dashed line. During operation of the Pelton nozzle, water flows between the nozzle needle 1 and the nozzle orifice 2 and presses against the insert ring 3, which thereby undergoes a bulging, which in turn leads to bending stress on the screws.

[0009] To avoid the associated safety risks (see above), the inventor came up with the idea of ​​completely eliminating the conventional screw connection and striving for a positive connection between the nozzle tip and the insert ring. The inventor chose a bayonet-type connection and designed it as advantageously as possible in various embodiments.

[0010] Fig. Figure 2 shows a Pelton nozzle according to the invention based on three different sections through the front area of ​​the nozzle mouthpiece 2. Compared to the Fig. 1, the nozzle nozzle tip 2 is designed to be extended forwards and completely surrounds the insert ring 3 in the installed position with respect to the axis of the nozzle needle 1, i.e. over the entire axial length of the insert ring 3. This has the advantage that the radial rigidity of the nozzle nozzle tip 2 increases and the entire cross-section becomes load-bearing. The insert ring 3 could, however, also protrude slightly beyond the nozzle nozzle tip in the axial direction or be set back slightly towards the front end of the nozzle nozzle tip. In the latter case, the nozzle nozzle tip 2 then completely surrounds the insert ring 3 in the installed position with respect to the axis of the nozzle needle 1. In any case, the nozzle nozzle tip 2 surrounds the insert ring 3 in the installed position over more than half the axial length of the insert ring 3 with respect to the axis of the nozzle needle 1. The axial length of the insert ring 3 is in Fig. 3 is illustrated in more detail and designated as L.

[0011] The nozzle orifice 2 has projections on the inside, which alternate with recesses. The insert ring 3 has projections on the outer circumference, which alternate with recesses. The projections of the insert ring 3 fit into the recesses of the nozzle orifice 2, so that the insert ring 3 can be inserted axially into the nozzle orifice 2. After inserting the insert ring 3, it is rotated relative to the nozzle orifice 2, whereby the projections of the insert ring 3 engage behind the projections of the nozzle orifice 2, viewed from the front, creating a positive connection. The upper part of Fig. 2 shows an area where the projections engage in the installed position as described. The middle part of Fig. Figure 2 shows the situation when axially inserting the insert ring 3 into an area where the nozzle orifice 2 has a recess. The insert ring 3 is already fully inserted. The projection on the insert ring 3 has been guided through the recess on the nozzle orifice 2. The lower part of Fig. 2 shows an area in which recesses in the nozzle mouthpiece 2 and in the insert ring 3 correspond to each other in the installed position.

[0012] For the strength of the connection, it is advantageous if the engagement ratio between projections and recesses in the nozzle orifice 2 and in the insert ring 3 is ideally 1:1. However, in order for the insert ring 3 to be inserted without problems under real conditions, the recesses in the nozzle orifice 2 must be slightly larger than the projections in the insert ring 3, so that the actually possible engagement ratio deviates slightly from 1:1. It is advantageous if the pitch with which the projections follow the recesses in the insert ring 3 is chosen to be as fine as possible, because then the form-fitting effect is distributed very evenly in the circumferential direction, and deformations of the insert ring 3 in the area of ​​the recesses are minimized. The inventor has recognized that a pitch in a range of 50% to 100% of the thickness D of the insert ring 3 is sufficient to keep such deformations within a tolerable range.The thickness D of the insert ring 3 is measured in the radial direction (see . Fig. 3), and the pitch is understood to be the distance that extends circumferentially over a complete projection and over the complete adjacent recess on the insert ring 3. When inserting the insert ring 3, it is therefore rotated by half the pitch relative to the nozzle mouthpiece 2.

[0013] The simplest way to manufacture the nozzle mouthpiece 2 and insert ring 3 is to first provide these parts with a circumferentially continuous shoulder in the area of ​​the later projections, which is then milled away in the area of ​​the later recesses.

[0014] Anti-twist protection is provided by at least one filler piece. Fig. Figure 3 shows an embodiment with a filler piece which is fixed by a radial screw. Fig. 3 the area corresponding to the lower part of Fig.2. The filler piece fills the area in which a recess in the nozzle mouthpiece 2 corresponds to a recess in the insert ring 3. The filler piece is designated 4 and ideally fills the specified area completely. It is therefore shaped like a segment of a cylindrical ring. This also ensures that the twist takes on the optimal value of half the pitch. The screws do not have to protrude into the filler pieces, but can also simply clamp the filler pieces. They can then take the form of grub screws. If as many areas as possible in which the recesses correspond to one another are filled in this way, the connection becomes increasingly stronger because the filler pieces 4 have a supporting effect. Since the filler pieces 4 are thus clamped between the nozzle mouthpiece 2 and the insert ring during operation of the Pelton nozzle, fixing screws can be dispensed with entirely.However, the number of filler pieces 4 also increases the effort required to replace the insert ring 3. On the other hand, by using filler pieces 4 in all gaps, the pitch can be selected to be larger. List of reference symbols 1 nozzle needle 2 nozzle mouthpiece 3 insert ring 4 filler piece

Claims

[1] Pelton nozzle with a nozzle needle (1) which can be moved along an axis, a nozzle mouthpiece (2) and an insert ring (3) which is connected to the nozzle mouthpiece (2) and which wraps around the axis, and wherein the nozzle mouthpiece (2) encloses the insert ring (3) in the installed position over more than half the axial length L of the insert ring (3) with respect to the axis, characterized bythat the connection between the nozzle mouthpiece (2) and the insert ring (3) is designed as a bayonet closure, and wherein the nozzle mouthpiece (2) has projections on the inside which alternate with recesses, and wherein the insert ring (3) has projections on the outside which alternate with recesses, and wherein the projections of the insert ring (3) fit into the recesses of the nozzle mouthpiece (2) so that the insert ring (3) can be inserted into the nozzle mouthpiece (2) in the axial direction, and wherein in the installed position the insert ring (3) is arranged such that the projections of the insert ring (3) engage behind the projections of the nozzle mouthpiece (2) when viewed from the front and thus bring about a positive connection between the insert ring (3) and the nozzle mouthpiece (2), and wherein in the installed position of the insert ring (3) at least one filler piece (4) is arranged such that it fills an area in which a recess in the nozzle mouthpiece (2) is provided with a Recess in the insert ring (3) corresponds. [2] Pelton nozzle according to claim 1, wherein the nozzle mouthpiece (2) encloses the insert ring (3) in the installed position over the entire axial length L of the insert ring (3) with respect to the axis.

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