EP1543922A1 - Blasting wheel with exchangeable vanes - Google Patents

Abstract

The vane has two partially curved, concave active surfaces (2, 2`), where curves of the surfaces are different with curve of one of the surfaces tending towards infinity. Each surface has a right part arriving at a proximal end of an axis, and a concave part arriving at a distal end of the axis. A common section (3) from the proximal end, extends by two curved parts (3`, 3``) that arrive at the distal end. An independent claim is also included for a high speed shot peening impeller including a set of vanes.

Description

Object of the invention

The present invention relates to a blasting turbine for centrifugal projection to high speed shot, such as round shot, angular hardness, glass beads, etc.

This type of turbine is used in a whole series of applications, by specific adaptation of the spray jet, for example starting from the most concentrated jet to the widest: rolling mill rolls, shot peening , foundry (cleaning of parts) and metal construction (stripping before painting), shot blasting, etc.

State of the art

We know shot blasting turbines comprising a series of paddles or blades driven in rotation about an axis. The pallets possess generally a single active surface, flat and wide uniform, which extends between a first end adjacent to that axis for the initial support of the shot to be shot and a distant second end of said axis for the final ejection thereof. For some reasons of balance, these pallets are usually arranged in pairs.

However, there are vane turbines straight lines arranged radially to the axis of rotation, so compared to the distribution device, and which have two potentially active surfaces. The pallets can therefore rotate in both directions of rotation or simply be returned in the turbine so to also use the other active face, when a single sense of rotation is imposed.

Centrifugal shot blasting turbines have for the purpose of projecting the shot with the largest possible speed while maintaining rotational speed within reasonable limits (1500 to 3000 revolutions / minute) and with the best resistance to wear due to the abrasion of the shot on the active faces of pallets.

With equal projection performance, the Centrifugal projection turbines far outweigh, in term of energy consumption (decrease of at least one factor 15), compressed air systems relaxed with injection of shot. So the use of these the latter leads to prohibitive costs, in particular during the treatment of large areas (energy consumption, conveying large volumes of compressed air on site, etc.) and noise pollution for operators.

A first evolution of turbines centrifugal shot blasting was brought by the replacement of the straight pallets by profiled pallets curve, for example concave or alternatively convex and concave (see for example US-A-4,277,965, DE-A-44 09 690, etc.).

Indeed, the design of turbines high capacity shot blasting must take into account that the axles with bearings impose on the turbines speeds limited rotation.

Thus, according to the patent application DE-A-44 09 690, belonging to the Applicant, for the same speed of rotation (fixed tangential speed) and an identical turbine diameter, it has been possible to increase thanks to the adoption of curved pallets the resulting speed of projection of the shot at the turbine outlet of about 25%. The angle α, represented in FIG. 1, between the tangent T ₁ (or T ₂ ) at the ejection edge of the pallet and a radial passing through the vertex of this edge is optimally between 0 and 60 ° , depending on the desired resultant speed performance and the coefficient of friction of the shot on the active face of the pallet.

In addition, the single curved pallet offers, besides a high projection speed for a moderate rotation speed, wear resistance exceptional when these pallets are made in specific alloys with ultra-high hardness such as carbide tungsten, ceramic, etc. Thus, we can arrive at a wear resistance at least 8 times longer than durations conventional pallets cast steel or cast iron.

Current turbines include a distributor (or squirrel cage) fed to the center in shot through a chute and turning into a piece of fixed control with calibrated light. Pallets themselves are placed in countersunk grooves of same shape as the pallets themselves; these grooves are machined in two flanges held jointly by one to the other by appropriate spacers and screws. The diameter of foot positioning of the pallets is chosen for a optimal adaptation of velocity vectors at this location, allowing capture of shot without shock, or with a minimum shock.

The peculiarity of single pallets curvature is to have a single active face and leads to the absolute obligation to turn in one direction from rotation, always the same. Indeed, according to these models of turbines, there are left turbines, that is to say turning left and straight turbines, that is to say turning right. These turbines are the picture one of the other in a mirror (orthogonal symmetry), in the same way with the right hand and the left hand.

Another disadvantage of non-turbines reversible single-sided active is their profile of wear, fatally limited to a single face and concentrated in the outermost region of the palette. So, we considers that the replacement of a pallet leads to the loss from 80 to 85% of the starting wear material, which is very expensive (eg tungsten carbide or ceramic).

The lack of reversibility of turbines the current state of the art may present a disadvantage, especially in terms of the cost of spare, because it requires left and right turbines.

Most non-vane turbines rights currently available commercially are not not reversible. Another reason for this state of affairs is that it is difficult to attach the pallets to their rotor, leaving both surfaces free of them. It is necessary to attach the pallets on their edge, which is difficult.

As already mentioned, the only turbines currently reversible on the market consist of straight pallets, with flat and radial active faces.

Goals of the invention

The present invention aims to propose a solution that makes it possible to overcome the disadvantages of the state of the art.

In particular, the invention aims to reconcile in a single solution the advantages of turbines one-sided curved shot blasting with the advantages of straight pallets with two active faces.

An object of the invention is therefore to propose a palette capable of projecting the shot at a speed almost identical to the speed of the curved palette, so more efficient about 25% in the resulting speed compared to the right pallet, for the same diameter of turbine and the same speed of rotation, but having the particularity to have two active faces, so to be reversible.

Main characteristic elements of the invention

A first object of the present invention relates to a pallet for high shot blast turbine speed, mounted essentially radially on a rotor to be rotated about an axis of it, and of which at least one wearing surface or active surface extends between a first proximal end of said axis where is performed taking care of the shot and a second end distal of said axis where is performed ejection of the shot, characterized in that the pallet has two active surfaces at least partially curved, concave and turning their concavity in essentially opposite directions.

Preferably, each active surface comprises in addition a straight part.

According to the invention, for each of the two active surfaces, the right part leads to the said proximal end of the axis and the concave portion leads to said distal end of the axis.

The invention is concretized in a manner advantageous because the pallet comprises a trunk common from the proximal end of the extended axis by two distinct branches ending in the end distal to the axis. The curvatures of both active surfaces may be the same or different. In the first case, the pallet has a symmetry with respect to the radial position in which the pallet is positioned in the turbine. In the second case, the curvature of one of the two active surfaces can tend to infinity, that is to say that one of the two active surfaces is essentially right.

The advantages of curved pallets of the state of the technique are taken up on behalf of the invention if the tangent to an active surface of the palette at the level the centrifugal exhaust of the shot forms an angle α, preferably less than 70 °, with the radial passing by the point of tangency.

Another advantageous feature of the invention is that the tangents to the two active surfaces curves at the centrifugal exhaust of the shot form between them an angle δ between 30 and 180 °, and preferably between 60 and 120 °.

According to a preferred embodiment, each slices of the pallet has a reinforcement or tenon for fixing the pallet in grooves machined in turbine flanges.

Still according to the invention, the two parts of active surface limiting the common core of the pallet are straight and form a small angle ε between them, preferably limited to 5 °.

Preferably, the right common core has a length between 20 and 80%, and preferably between 40 and 60% of the total length of the pallet. Of preferably again, the thickness of the common core grows with the distance to the outside, from the edge of entrance.

Without limitation for the invention, the trunk common right may also not be present, each active surfaces then being entirely curved.

Preferably, the internal faces of the two aforementioned branches of the pallet, which are therefore not active, are connected, at the level of a region called "chalice", by a circular connection, able to marry exactly the shape of a machined groove in the face internal flange or that of an abutment axis or a end of axis-stop.

The skilled person will not be surprised that, according to the invention, the pallet can be produced aforesaid cast steel alloy or forged treated, but preferably ultra-hard alloy such as carbide tungsten, without being limiting to the invention, or ceramic.

• un distributeur, encore appelé cage d'écureuil, solidarisé à l'axe et tournant à la vitesse du rotor, alimenté en grenaille en son centre via un conduit ou une goulotte et coiffé par une pièce de contrôle fixe, de position angulaire réglable et présentant une lumière calibrée pour l'échappement de la grenaille ;
• un premier et un deuxième flasques espacés limitant latéralement la partie active de la turbine ;
• une pluralité de palettes telles que décrites ci-dessus, disposées de préférence radialement, interposées au niveau de leurs tranches respectives entre lesdits flasques et solidarisées à ceux-ci.

A second aspect of the invention relates to a high speed shot blast turbine, comprising:

• a distributor, also called squirrel cage, secured to the axis and rotating at the speed of the rotor, fed with shot in its center via a conduit or chute and capped by a fixed control piece, adjustable angular position and presenting a calibrated light for the escape of the shot;
• first and second spaced flanges laterally limiting the active portion of the turbine;
• a plurality of pallets as described above, preferably arranged radially interposed at their respective edges between said flanges and secured thereto.

According to a first execution modality preferred embodiment of the invention, said pallets are secured to flanges by embedding them in grooves machined on the inner face of each flange and marrying the shape of the palette.

According to a second execution modality preferred embodiment of the invention, said pallets are secured to the flanges by means of abutment pins or ends of abutment axes and small recesses machined in the flanges to accommodate the foot of the pallets.

According to a modality of execution still advantageously, each pallet is positioned on the rotor of way such that an axis of the pallet is mounted translated of a given distance, in the direction of rotation, by relative to the radial while being parallel to it. This configuration allows support for the shot at the foot of each pallet with a zero shock, if the distance is chosen appropriately.

According to more general characteristics of the turbine of the invention, the speed of ejection of shot at the outlet of the turbine is between 40 and 200 m / s, the speed of rotation of the turbine is between 1000 and 5000 rpm, preferably between 1500 and 3000 rpm. and the diameter of the flanges, and therefore the total diameter of the turbine is between 200 and 600 mm.

A third subject of the invention concerns a flange for blast turbine as described above, said flange comprising a plurality of openings Circulars made through the flange for laying axes-abutment or stop-axis ends and a plurality of aforementioned small fittings or a plurality of supporting grooves adapted to the contour of the pallets, and in particular the pins provided for this purpose. These grooves are machined on the inner surface side of the flange for embedding the pallets of the invention.

Brief description of the figures

Figure 1, already mentioned, represents schematically a sectional view of a form of execution a "gamma" shape pallet according to the present invention.

Figure 2 schematically represents the pallet of Figure 1 integrated into machined grooves in the flanges.

Figure 3 shows a flange section machined to accommodate said pallet.

Figure 4 schematically represents two other methods of fixing pallets. In Figure 4a, the calyx of the pallet is supported on an axis-stop fixed by the two flanges enclosing the pallet. In Figure 4b, we have the same layout where the thrust axis is replaced by two ends of abutment pins located in each flange.

Figure 5 shows a palette where the parts straight lines disappeared and are replaced by curves continuous extending to the foot of the pallet.

Figure 6 shows a two-sided pallet in accordance with the invention but offset from the radial for zero shock support at the foot of the palette.

Figure 7 shows a palette of which one first active face consists of a straight part and of a curved part and of which a second active face is straight.

Description of a preferred embodiment of the invention

To achieve the objective of the invention, that is to say, especially to maintain an ejection speed close to that obtained with the curved pallet, for a same rotation speed and the same turbine diameter, it is necessary that the tangent to the pallet at the level of the escape of the shot makes an angle α with the radial passing through this same point, similar to the existing situation in the curve palette (see Figure 1).

Surprisingly, he then came to the Applicant's spirit to apply the principle of superposition of two curved palettes, one against the other, to obtain two opposite active faces with a output as shown in Figure 1. Note that condition is fulfilled if pallet 1 has a rectilinear common core 3 and two ejection parts 3 ', 3 "curves meeting high ejection criteria aforementioned speed, for the same rotational speed of the turbine.

The so-called "gamma" shape pallet the object of the present invention combines the high output speeds with two active faces 2, 2 'allowing to rotate the turbine indifferently in one direction or in the other, or just giving the possibility to return the pallet in the turbine for get a doubled life for the pallet.

According to a preferred embodiment of the invention, the pallet 1 for blast turbine is characterized by a rectilinear portion 3 having a length The corresponding to a fraction of the total length L of pallet, which is close to the difference between largest radius R and the smallest radius r of the flange 10 (see Figure 1). This straight part is extended by two curved parts 3 ', 3 "offering ejection speeds significantly larger than a straight pallet mounted in a turbine of the same diameter and rotating at the same speed.

Ideally, the angle δ formed by the two tangent to the escape of the shot at the level of two active faces must be between 60 and 120 °, said angle depending on the diameter of the turbine in question and the desired performance. An angle δ lower than 60 ° or greater than 120 ° may also be suitable but making a less suitable palette drawing.

In the case of an angle δ lower than 60 °, for example, the pallet has very large wings long. Moreover, in the case of a larger angle δ than 120 °, the wings of exit are very curved and are therefore much more sensitive to wear.

According to a particular embodiment of the invention, the blasting turbine pallet includes a common part supporting both sides active in the palette. The two active faces of this common part are advantageously straight and form a slight angle ε between them, for example between 1 and 5 °. An angle ε = 0 could also be suitable but with of useless material.

Preferably, the length L 'of the part common right represents a fraction between 40 and 60% of the total length L of the pallet.

As the wear is getting bigger and bigger at count of foot 5 of the pallet, it is necessary that, in this straight part of the pallet, with diameters bigger and bigger, the thickness e increases with the distance from the entry edge 5, hence the slight angle ε.

According to the invention, as shown in FIGS. 2 and 3, the "gamma" pallets 1 are advantageously secured to flanges 10, by means of grooves 11 machined in each flange and marrying the shape of the tenons 4 and 4 '(Fig. 1) of the pallet. Studs 4 and 4 'create a channel that keeps the shot on the active side and thus prevent the use of flanges in the area close to the active face of the pallet, or active faces when the turbine rotates in both directions of rotation.

Milled edges in flanges lean against the edge 12 of the bottom of the chalice of the pallet and hold it radially in the rotor consisting of two flanges (Figure 3).

Figures 4a and 4b show another arrangement where the flanges do not have grooves, of "gamma" form but are held radially by complete thrust axes 13 or end stops 14, 14 'leaning in the bottom of the chalice 12 of the pallet while the foot of the pallet 5 gets into a small groove 16 prevents the pallet from rotating around the axis 13 or 14, 14 '.

According to a still preferred embodiment, the pallet is made in such a way that the faces internal, therefore not active, of the two curved parts 3 ', 3 " are connected in a circular connection 12, in which just fits the edge of the grooves 15 or in the other mode of attachment, the axis-abutment 13 or the ends stop axis 14, 14 '(FIGS. 3, 4a and 4b).

The manufacturing method shown in the figure 5, where the pallets no longer have a straight portion, is rather intended for achievements in less noble alloys, such as cast steel where the weight per pallet has less importance on the cost price.

In "gamma" vane turbines radial, the resultant of the vectors speed of entry, at the foot level 5, produces a slight shock on the active side, this very weak shock does not hurt the good turbine operation.

If you want a completely shocked treatment no one at the foot of the pallet, it is necessary to translate the axis of the pallet of a distance Ω, in the direction of rotation, staying parallel to the radial. The value of Ω depends the size of the r and r rays of the turbine. In this case, the turbine is no longer reversible but the pallet alone remains perfectly reversible and also has two sides potentially active (Figure 6).

According to yet another form of advantageous embodiment of the invention, illustrated in FIG. FIG. 7, the pallet presents a first active face which consists of a straight part and a curved part, as described above, and a second active face straight. This embodiment can be used in turbines intended to rotate at two different speeds, or having to offer differentiated performances, according to the direction of rotation adopted.

• les palettes présentant deux faces actives sont réversibles sur une turbine donnée : lorsque la face active opérationnelle est usée, il suffit de faire tourner la turbine selon l'autre sens de rotation, pour bénéficier d'une face active neuve. Dans le cas d'installations comportant des turbines disposées par paires, tournant selon des sens opposés et dont les pinceaux d'éjection sont symétriques par rapport à un plan médian pour assurer une intensité uniforme de grenaillage, il suffit tout simplement d'intervertir les deux turbines d'une même paire, pour rester dans la même configuration de projection et user l'autre face active. On peut également, sur une turbine donnée, retourner toutes les palettes. Ces mesures permettent de doubler la durée de vie des palettes, ce qui constitue un avantage économique considérable, vu le coût extrêmement élevé des palettes en alliage ultra-dur et tenant compte du fait que les coûts de maintenance, en particulier de remplacement des pièces d'usure, peuvent représenter jusqu'à 40% du coût total de la maintenance d'une installation de grenaillage ;
• les palettes à double surface active de l'invention présentent les mêmes avantages que celles à surface active unique courbe, à savoir une vitesse d'éjection supérieure à celle des palettes droites, pour un même diamètre de turbine et pour une même vitesse de rotation de celle-ci ;
• le dispositif de fixation des palettes au rotor selon l'invention libère la face opposée à la face actuellement active et préserve la réversibilité totale de la turbine.

The present invention has the following advantages over the state of the art:

• pallets having two active faces are reversible on a given turbine: when the operational active face is worn, it is sufficient to rotate the turbine in the other direction of rotation, to benefit from a new active face. In the case of installations comprising turbines arranged in pairs, rotating in opposite directions and whose ejection brushes are symmetrical with respect to a median plane to ensure a uniform intensity of shot blasting, it suffices to simply reverse the two turbines of the same pair, to stay in the same projection configuration and use the other active side. It is also possible, on a given turbine, to return all the pallets. These measures make it possible to double the lifespan of the pallets, which constitutes a considerable economic advantage, given the extremely high cost of the pallets made of ultra-hard alloy and taking into account the fact that the maintenance costs, in particular the replacement of wear, can represent up to 40% of the total cost of maintenance of a shot blasting facility;
• the double active surface pallets of the invention have the same advantages as those with a single curved active surface, namely an ejection speed greater than that of the straight pallets, for the same turbine diameter and for the same speed of rotation of this one;
• the device for fixing the pallets to the rotor according to the invention releases the face opposite to the currently active face and preserves the total reversibility of the turbine.

Claims (23)

Pallet (1) for a high-speed shot blast turbine, mounted substantially radially on a rotor to be rotated about an axis thereof, and having at least one wear surface or active surface extending therebetween first proximal end of said axis where the taking into charge of the shot is carried out and a second end distal from said axis where the shot is ejected, characterized in that the pallet (1) has two active surfaces (2, 2 '). ), at least partially curved, concave and turning their concavity in essentially opposite directions. Pallet according to claim 1, characterized in that each active surface further comprises a straight portion. Pallet according to claim 1 or 2, characterized in that , for each of the two active surfaces (2, 2 '), the straight portion ends at said proximal end of the axis and the concave portion ends at said distal end of the axis. Pallet according to any one of claims 1 to 3, characterized in that the pallet comprises a common trunk (3), starting from the proximal end of the axis, extended by two separate branches (3 ', 3 ") terminating at the distal end of the axis. Pallet according to any one of claims 1 to 4, characterized in that the curvatures of the two active surfaces (2, 2 ') are identical. Pallet according to any one of claims 1 to 4, characterized in that the curvatures of the two active surfaces (2, 2 ') are different, possibly with the curvature of one of the two active surfaces tending towards infinity, c' that is to say with one of the two active surfaces essentially straight. Pallet according to claim 5, characterized in that the pallet has a symmetry with respect to the radial (X ') in which is positioned the pallet in the turbine. Pallet according to any one of the preceding claims, characterized in that the tangent (T1, T2) to an active surface (2, 2 ') of the pallet at the level of the centrifugal escapement of the shot forms an angle α, of preferably less than 70 °, with the radial (X) passing through the point of tangency. Pallet according to any one of the preceding claims, characterized in that the tangents (T1, T2) to the two curved active surfaces at the level of the centrifugal escapement of the shot form between them an angle δ of between 30 and 180 °, and preferably between 60 and 120 °. Pallet according to any one of the preceding claims, characterized in that each of its slices has a reinforcement or tenon (4, 4 ') for fixing the pallet in grooves (11) machined in the flanges (10) of the turbine . Pallet according to any one of claims 4 to 10, characterized in that the two active surface portions limiting the common trunk (3) of the pallet are straight and form a small angle ε between them, preferably limited to 5 °. Pallet according to claim 11, characterized in that the right common trunk (3) has a length (L ') of between 20 and 80%, and preferably between 40 and 60%, of the total length (L) of the pallet . Pallet according to claim 11, characterized in that the right common trunk (3) has a length (L ') zero. Pallet according to claim 11 or 12, characterized in that the thickness (e) of the common core increases with the distance to the outside, from the input edge (5). Pallet according to claim 11, characterized in that the internal faces of the two aforementioned branches (3 ', 3 "), thus non-active, are connected by a circular connection (12), conforming exactly to the shape of a groove (11) machined in the inner face of a flange (10) or the shape of an abutment axis (13) or a stop-axis end (14, 14 '). Pallet according to any one of the preceding claims, characterized in that it is made of treated cast or forged steel alloy, preferably ultra-hard alloy such as tungsten carbide, or ceramic. High speed shot blast turbine, characterized in that it comprises: a distributor, also called squirrel cage, secured to the axis and rotating at the speed of the rotor, fed with shot in its center via a conduit or chute and capped by a fixed control piece, adjustable angular position and presenting a calibrated light for the escape of the shot; first and second spaced flanges laterally limiting the active portion of the turbine; a plurality of pallets (1), according to any preceding claim, arranged substantially radially, interposed at their respective edges between said flanges (10) and secured thereto. Shot blasting turbine according to claim 17, characterized in that said pallets (1) are secured to the flanges (10) by embedding in grooves (11) machined on the inner face of each flange (10) and matching the shape of the pallet or by means of abutment pins (13) or stop-axis ends (14, 14 ') and small recesses (16) machined in the flanges to accommodate the foot of the pallets. Turbine according to claim 17 or 18, characterized in that each pallet is positioned on the rotor in such a way that an axis of the pallet is mounted translated by a given distance (Ω), in the direction of rotation, relative to to the radial while being parallel to it. Turbine according to any one of claims 17 to 19, characterized in that the ejection speed of the shot at the outlet of the turbine is between 40 and 200 m / s. Turbine according to any one of claims 17 to 20, characterized in that the speed of rotation of the turbine is between 1000 and 5000 rpm, preferably between 1500 and 3000 rpm. Turbine according to any one of claims 17 to 21, characterized in that the diameter of the flanges, and therefore the total diameter of the turbine, is between 200 and 600 mm. Flange (10) for a shot blast turbine according to any one of claims 17 to 23, characterized in that it comprises a plurality of circular openings made through the flange for the installation of abutment axes (13) or abutments (14, 14 ') and a plurality of corresponding small abutments (16) or a plurality of supporting grooves (11), adapted to the contour of the pallets, in particular studs provided for this purpose, and machined on the side of the inner surface of the flange, for the positioning of pallets (1) according to any one of claims 1 to 16.

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