FR2702983A1 - Shot blasting turbine. - Google Patents

Abstract

The high speed shot blasting turbine is equipped with an even or odd number of vanes or vanes (1 ') in anti-wear material with a concave and circular long profile, including the initial support surface (22 ) forms an angle (alpha) less than 90degree with the tangent and whose ejection edge (24) forms an angle (gamma) of 0degree to 60degree with respect to a radial passing through the apex of this edge.

Description

BLASTING TURBINE

  Summary of the invention The present invention relates to a shot blasting turbine for the high speed projection of shot, this turbine comprising a series of vanes or blades driven in rotation about an axis and including a support surface s extends between a first end adjacent to said axis for the initial handling of shot-blasting and a second end remote from said axis for ejecting shot, said first ends being located at a distance from said axis less than the

  distance between a second end of the axis.

  Each support surface has a concave profile and circular curvature, the tangent of said profile in the vicinity of the first end making an angle less than 900 with the tangent, in the vicinity of said end, to a cylinder of revolution around the axis, while the tangent of said profile in the vicinity of the second end forms an angle less than 600 relative to a radial extending between said axis and

said second end.

  State of the art Shot blasting turbines are known in the state of the art For example, documents US 3,034,264, US 3,977,128, 4,377,924 and 4,020,596 describe shot blasting machines comprising a blasting turbine and their uses These documents are incorporated into this specification by reference to describe machines using blasting turbines and possible uses of

blasting turbines.

  In the current state of centrifugal projection turbines, the main advantage of shot blasting turbines projecting grains by centrifugal action is the low energy consumption compared to the compressed air system with injection of

  shot, with obviously equal projection performance.

  A 10 mm diameter expanded air projection nozzle - requires a 60 CV compressor, while a projection turbine does the same

  work with only 4 CV installed on the spindle.

  The turbines with straight blades take charge of the shot, which leaves the distributor with a fairly violent shock, capable even of breaking the shot

  steel, very fragile for high hardness.

  The present invention aims to remedy this drawback and relates to a high-performance projection shot blasting turbine, suitable in particular in shot blasting machines where it projects metallic particles onto the surfaces to be stripped or

treat in roughness value.

Brief description of the invention

  The subject of the present invention is a shot blasting turbine, the paddles or blades of which have a determined profile capable of imparting to the grains the highest possible speed, while maintaining a diameter and a rotational speed which are clearly lower than

for straight blades.

  The innovation of this blading or pallet is on two levels:

  1 at the level of initial grain management.

  2 at the resulting ejection speed.

  The shot blasting turbine for high speed shot projection comprises a series of vanes or blades driven in rotation about an axis and of which a support surface extends between a first adjacent end of said axis for support initial shot to be thrown and a second end remote from said axis for ejecting the shot, said first ends being located at a distance from said axis less than the distance separating a second end from the axis, each support surface has between its said first and second ends a concave profile and circular curvature, the tangent of said profile in the vicinity of the first end making an angle a less than 900 with the tangent, in the vicinity of said first end, to a cylinder of revolution around the axis whose radius corresponds to the distance separating the first end from the surface of taken e under considered load and said axis, while the tangent of said profile in the vicinity of the second end forms an angle y less than 600 relative to a radial

  extending between said axis and said second end.

  Advantageously, each support surface has between its said first and second ends a concave profile and circular curvature, the tangent of said profile in the vicinity of the first end making an angle a less than 450 with the tangent in the vicinity of said first end to a cylinder of revolution around the axis whose radius corresponds to the distance separating the first end from the support surface considered and said axis, while the tangent of said profile in the vicinity of the second end forms an angle y less than 600 relative to a radial extending between said axis and

said second end.

  According to embodiments, each blade or pallet is provided with two fixing lugs housed in two turbine flanges or is provided behind its active face with a rib, with hole and cutout, used for its fixing. According to another embodiment, the blades or vanes are an integral part of a drive flange. Other peculiarities and details of

  the invention will emerge from the detailed description

  following in which reference is made to the accompanying drawings.

Brief description of the drawings

  In these drawings given by way of example only: FIG. I is a diagrammatic view partially in section of a current straight bladed turbine carrying out an initial impact treatment; Figure 2 shows a profile of an active surface of a pallet of a turbine according to the invention, said surface being concave and with correct handling; Figure 3 is an enlarged view of the active area at the level of initial care; Figure 4 is a sectional view of a profile of another embodiment of a pallet of a turbine according to the invention at high ejection speed; Figures 5 and 6 are respectively a front view of a turbine according to the invention with four blades and a section along the lines VI-VI of Figure 5, the blades being adjacent to the drive flange; Figures 7 and 8 are respectively a side view and a rear side view of an alternative embodiment of blading according to the invention, the blades being removable and held between two flanges, one of which is the flange of drive, and Figures 9 to 11 are respectively a partial sectional view of a turbine, a sectional view along lines XX of Figure 9 and a view

partial perspective.

  Description of embodiments

  For fragile shot, used for difficult surface shot blasting applications, such as rolling mill rolls for example, it is important to take care of the shot as gently as possible, without shock, in order to

  preserve the shot and avoid breaking it.

  As can be seen in FIG. 1, the straight pallets 100 or even convex currently produced tend to break the shot at the entrance. On the other hand, the concave surfaces 22 of the pallet 1, such as those shown in the sketch of FIG. 2, greatly reduce the shock effect and therefore make it possible to avoid

  breakage of the shot as soon as it is taken over.

  As can be seen in FIG. 1, the pallets are driven in rotation (speed w) so that the shot 101 leaving the dispenser is brought gradually by the effect of centrifugal force in the vicinity of the free edge 102 of a pallet 100 o the shot 101 leaves the turbine with a speed VR, speed resulting from the tangential speed V, and the

radial speed V ,.

  At the outlet of the distributor, the shot has a low speed, the direction of which is that indicated by the vector B of FIG. 2 The vector A, perpendicular to the radius r, indicates the speed of the material point of the blade root. Figure 3 shows, in an enlarged manner, the

  velocity vectors A and B at radius r 1.

  A gentle handling of the shot is imperative for small turbines, which must turn very quickly to reach an ejection speed

sufficiently high resultant.

  Contrary to what has already been done, it is not a question of making an impact start surface parallel to the speed vector of the shot at the outlet of the distributor, vector B, but rather of making a support surface. as close as possible to the direction opposite the velocity vector at this level of diameter. Some manufacturers have set the leading edge of the vane tangent to vector B, which is a fundamental error for correct handling of shot. This gives the dotted profile (Figures 2 and 3), profile where the initial take-up of shot is very poor This profile greatly reduces take-up, which leads to a reduction in the admissible flow rate by this turbine Indeed, this type of profile rejects part of the shot towards the center thus preventing its take-up

in charge.

  It is therefore necessary for the tangent to the surface of the initial support edge to be as close as possible to the angle of the direction of the vector B, speed vector of the shot at the outlet of the distributor. Obviously, it is not possible to place the leading edge of the blade as an extension of vector B (or A for that matter), because the leading edge has a thickness which prevents these directions from coinciding. , it is advantageous that the leading edge is closest to this direction, taking into account the thickness. As can be seen in FIG. 2, the turbine according to the invention is placed in a body 20

  allowing the ejection of shot through line 200.

  This turbine comprises a series of pallets 11 (two pallets being shown) driven in rotation (arrow w) around an axis 21 The pallets have a surface 22 for taking care of the shot 101 to be projected, surface 22 which extends between one end or edge 23 adjacent to the axis 21 (edge 23 or end for the initial handling of the shot to be shot) and one end or edge 24 distant from said axis 21 (edge for the ejection of the shot) The edge 23 is located at a distance r 1 from the axis 21, distance r 1 less than

  the distance r 2 separating the edge 24 from the axis 21.

  The support surface has between its edges 23, 24 a concave and circular profile (radius R). The tangent t 23 forms an angle a with the tangent t of a cylinder of revolution around the axis 21 and whose radius is rj, tangent t in the vicinity of the edge 23 This angle a is advantageously less than 450, thus ensuring a excellent support (gentle support) Support will be all the better as the angle a approaches 0 (for

example less than 150).

  The tangent t 24 of said profile in the vicinity of the edge 24 forms an angle y with respect to a radial T extending between the axis 21 and said edge 24 This angle

is between O and 600.

  The profile of the blade or of the pallet is designed according to the invention so as to eject the shot with a resulting speed as high as possible, for a determined speed of rotation,

  preference as low as possible.

  In other words, for the resulting speed VR (figure 4) to be maximum for a fixed tangential speed V, (therefore W fixed since V, = wr 2, with W in rad / sec), the angle y (angle that does the ejection edge 24 relative to a radial T passing through the top of this edge) is between 0 and 600, and this

  depending on the type of shot used.

  The angle y is fixed by the speed to be obtained as a function of the speed of rotation of the blades 1 (N revolutions / minute), but also as a function of the admissible degree of wear of the blades It is obvious that high angles y can cause far too much wear and tear, requiring blading

very high hardness.

  The relative speed Vr combined with the speed V, gives the resulting speed Vr When the angle Y increases, the relative speed Vr decreases, but the composition of the two speeds can give a higher resulting speed VR, at rotation speed (N revolutions / minute) equal Depending on the shot

  projected, this optimum angle varies from 0 to 600 En-

  below or above this value, the composition of the two speeds V, and Vr gives a resulting speed more

  low at equal speed of rotation N.

  The profile of this blade is of circular curvature; whose radius is chosen according to the dimensions r 1 and r 2 of the turbine to arrive at the desired angle y Choosing a circular profile leading to a better VRIN ratio is essential for specific shot blasting applications Indeed, for a small turbine , the VR speed gain for a given rotation speed is significant. Indeed, for known turbines, it is necessary to turn at very high speeds (+ 20%) to achieve the same result. Similarly, in shot peening of rolling mill rolls, the tendency is to increase the hardness of the roll tables to better resist wear. Consequently, shot peening of the rolls

  becomes more and more difficult, if not impossible.

  It should be noted that the solution consisting in turning faster to reach a higher speed, risks breaking the grains at the entrance, during the initial treatment. In addition, the increase in speed leads to an increase in forces. unbalance proportional to the square of the speed of rotation. The invention therefore makes it possible to avoid these drawbacks because it allows high VR speeds for lower rotation speeds. The design of the turbine according to the invention has made it possible to build miniature shot blasting machines with a turbine, which can be operated manually. this type of turbine therefore makes it possible to build shot blasting machines with a portable turbine but also to build shot blasting turbines requiring very high spraying speeds, such as those used in rolling mill blasting machines. These turbines can also be used in the shot peening, or the high speeds of

  projection are often necessary.

  Figures 5 and 6 show an embodiment of this type of turbine with four blades 1, meeting the performance conditions recommended, for a type of

angular shot chosen.

  The blades 1 of this embodiment are part

  integral with the drive flange 3 (Figures 5 and 6).

  This flange 3 has orifices providing passage to bolts 25 for its attachment to a shaft

26.

  Another embodiment of blading 1 according to the invention is that shown in Figures 7 and 8, where the hole 4 and the cutout 5 in the rib 6 are used for fixing the blading. It can be seen on the active face 22 that the initial load 23 Another blade arrangement is shown in FIGS. 9 to 11 The active face 22 is indicated there This blade is not provided with a back rib The two pins 9 serve for fixing the blade in the two 3 A, 3 B flanges

partially represented.

  To increase the aggressiveness of the projection, it may be useful to make a channel 27, the width of which decreases as the radius r increases. Another solution is to make a channel, the profile of which in cross section is slightly curved This way of building the vane concentrates the shot in the center,

just at the time of ejection.

  The blades or pallets according to the invention are advantageously made of a very hard, anti-wear material, such as tungsten carbide or in all

  other more or less efficient anti-wear material.

  The turbine can be cast in one piece with the blades incorporated and in one piece It can also have a different number of blades, even or odd, for example from 2 to 20, in particular of

4 to 7.

  Of course, it would not depart from the field of the invention to produce blades having an active form as claimed but whose mode of

  fixing and / or the external shape would be different.

  Only the active face 22 is important in the turbine

according to the invention.

Claims (5)

  1 shot blasting turbine for high speed protection of shot blasting, this turbine comprising a series of vanes or blades driven in rotation about an axis and of which a support surface extends between a first adjacent end of said axis for the initial handling of shot to be shot and a second end remote from said axis for ejecting shot, said first ends being located at a distance from said axis less than the distance separating a second end from the axis, characterized in that each support surface has between its said first and second ends a concave profile and circular curvature, the tangent of said profile in the vicinity of the first end making an angle a less than 900 with the tangent, in the vicinity of said first end, to a cylinder of revolution around the axis whose radius corresponds to the distance separating the pr first end of the support surface considered and said axis, while the tangent of said profile in the vicinity of the second end forms an angle y less than 600 relative to a radial extending between said axis and said second end.   2 turbine according to claim 1, characterized in that each support surface has between its said first and second ends a profile, concave and circular, the tangent of said profile, in the vicinity of the first end, making an angle a less than 450 with the tangent, in the vicinity of the said first end, to a cylinder of revolution about the axis whose radius corresponds to the distance separating the first end from the surface of   support considered and said axis.   3 Turbine according to claim 1 or 2, characterized in that each blade is provided with two fixing lugs housed in the two turbine flanges. 4 turbine according to claim 1 or 2, characterized in that each blade is provided behind its active face with a rib, with hole and cut out, used for its fixing.   5 Turbine according to claim 1 or 2, characterized in that the blades are part   part of a training flange.