GB2276341A

GB2276341A - Shot-blasting turbine

Info

Publication number: GB2276341A
Application number: GB9405733A
Authority: GB
Inventors: Leon Rutten
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-03-24
Filing date: 1994-03-23
Publication date: 1994-09-28
Anticipated expiration: 2014-03-23
Also published as: FR2702983B1; FR2702983A1; GB2276341B; NL194785C; NL9400462A; GB9405733D0; NL194785B; DE4409690A1; DE4409690B4; BE1006808A6

Description

SHOT-BLASTING.TURBINE The subject of the present invention is a

shotblasting turbine for the high-speed projection of shot, this turbine comprising a series of blades or vanes which are driven in rotation about an axis and a reception surface of which extends between a first extremity adjacent to the said axis for the initial reception of shot to be projected and a second extremity remote from the said axis for the ejection of the shot, the said first extremities being situated at a distance from the said axis less than the distance separating a second extremity from the axis. Each reception surface presents a concave profile of circular curvature, the tangent of the said profile in the vicinity of the first extremity making an angle of less than 90 with the tangent, in the vicinity of the said extremity, to a cylinder of revolution about the axis, whereas the tangent of the said profile in the vicinity of the second extremity makes an angle of less than 60 with respect to a radial line extending between the said axis and the said second extremity.

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 shot-blasting turbine and their uses. These documents are incorporated into the present specification for reference in order to describe machines using shot-blasting turbines and Dossible uses of shotblasting turbines.

In the present state of centrifugal projection turbines, the main advantage of shot-blasting turbines projecting particles by centrifugal action is the low consumDtion of energy in comparison with the expanded compressed air system with injection of shot, for equal projection performance, of course.

A small nozzle for projection with expanded air of 1Omm in diameter requires a compressor of 60 metric horse-power, whereas a projection turbine carries out the same work with only 4 installed metric horse-power at the spindle.

Turbines with straight vanes receive the shot, which leaves the distributor with a fairly violent shock, capable even of breaking steel shot, which is very brittle at high levels of hardness.

The present invention aims to remedy this dis- advantage and has as its object a shot-blasting turbine for high performance projection, suitable in particular in shot-blasting machines where it projects metal particles onto surfaces to be scoured or to be treated to a roughness value.

is The present invention has as its object a shotblasting turbine the blades or vanes of which have a specific profile capable of imparting to the particles the highest possible velocity while maintaining a diam- eter distinctly smaller and a rotational velocity distinctly slower than with straight vanes.

The innovation of this vane or blade lies at two levels:

1. at the level of the initial reception of the part- icles. 2. at the level of the resultant ejection velocity.

The shot-blasting turbine for the projection at high-speed of shot comprises a series of blades or vanes which are driven in rotation about an axis and a recep tion surface of which extends between a first extremity adjacent to the said axis for the initial reception of shot to be projected and a second extremity remote from the said axis f or the ejection of the shot, the said first extremities being situated at a distance from the said axis less than the distance separating a second extremity from the axis, each reception surface presents between its said first and second extremities a concave prof ile of circular curvature, the tangent of the said profile in the vicinity of the first extremity making an angle a of less than 900 with the tangent in the vicinity of the said first extremity, to a cylinder of revolution about the axis, the radius of which corresponds to the distance separating the first extremity of the reception surface in question and the said axis, whereas the tangent of the said profile in the vicinity of the second extremity makes an angle V of less than 60 with respect to a radial line extending between the said axis and the said second extremity.

In an advantageous manner, each reception surface presents between its said first and second extremities a concave profile of circular curvature, the tangent of the said profile in the vicinity of the first extremity making an angle a of less than 45 with the tangent, in is the vicinity of the said first extremity, to a cylinder of revolution about the axis, the radius of which corresponds to the distance separating the first extremity of the reception surface in question and the said axis, whereas the tangent of the said profile in the vicinity of the second extremity makes an angle y of less than 60 with respect to a radial line extending between the said axis and the said second extremity.

According to some embodiments, each vane or blade is provided with two mounting studs housed in two turbine flanges or is provided behind its active face with a rib, with hole and cutaway, serving for its mounting.

According to another embodiment, the vanes or blades form an integral part of a drive flange.

Other features and details of the invention will become apparent from the following detailed description in which reference is made to the accompanying drawings.

In these drawings given solely by way of example: - Figure 1 is a diagrammatic view partially in cross- section of a usual turbine with straight vanes executing a recention with initial shock; - Figure 2 shows a prof ile of an active surf ace of a turbine blade according to the invention, the said surface being concave and with correct reception; Figure 3 is a view to a larger scale of the active surface at the level of the initial reception; - Figure 4 is a view in cross-section of a prof ile of another embodiment of a turbine blade according to the 5 invention with high ejection velocity; - Figures 5 and 6 are respectively a f ront view of a turbine according to the invention with four vanes and a cross-section along lines VI-V1 of Figure 5. the vanes being contiguous to the drive flange; - Figures 7 and 8 are respectively a profile view and a rear face view of a variant embodiment of a vane according to the invention, the vanes being removable and maintained between two flanges, one of which is the drive flange, and - Figures 9 to 11 are respectively a partial view in cross-section of a turbine, a view in cross-section along lines X-X of Figure 9 and a partial view in perspective.

For brittle shott used for difficult surface shot-blasting applications, such as rolling-mill rolls for example, it is important to receive the shot in the gentlest possible mannere without any shock, in order to preserve the shot and to avoid breaking it.

As seen in Figure 1, the straight or even convex blades 100 produced at present have a tendency to break the shot upon entry. In contrast, the concave surfaces 22 of the blade 1, such as those found again in the sketch of Figure 2, substantially reduce the shock effect and therefore make it possible to avoid breaking the shot as soon as it is received.

As seen in Figure 1, the blades 100 are driven in r otation (velocity w) so that the shot 101 leaving the distributor is brought progressively by the effect of the centrifugal force to the vicinity of the free edge 102 of a blade 100 where the shot 101 leaves the turbine with a velocity V,, the resultant velocity of the tangential velocity V. and of the radial velocity V,,.

At the outlet from the distributor, the shot possesses a low velocity, the direction of which is that indicated by the vector B of. Figure 2. The vector A, perpendicular to the radius r, indicates the velocity of the physical point of the foot of the vane.

Figure 3 shows, in a magnified manner, the 5 velocity vectors A and B at the radius ri.

A gentle reception of the shot is imperative for small turbines, which must rotate very quickly in order to attain a sufficiently high resultant ejection velocity.

Contrarily to what has already been done, it is not a question of forming an initial impact surface parallel to the velocity vector of the shot at the outlet from the distributor, vector B, but in fact of forming a reception surface as close as possible to the direction opposite to the velocity vector at this level of diam- eter. Some constructors have placed the leading edge of the vane tangent to the vector B, which is a fundamental error for a correct reception of the shot. The profile 20 1000 in broken lines (Figures 2 and 3) is thus obtained, on which profile the initial reception of the shot is very poor. This profile substantially reduces the reception, which leads to a reduction in the flow rate admissible by this turbine. In fact, this type of profile throws some of the shot back towards the centre, thus preventing its reception.

It is therefore necessary for the tangent to the surface of the initial reception edge to be as close as possible in angle to the direction of the vector B, the velocity vector of the shot at the outlet from the distributor.

Of course, it is not possible to place the leading edge of the vane in the extension of the vector B (or A moreover), because the leading edge has a thick- ness which prevents these directions from coinciding. This said, it is advantageous for the leading edge to be as close as possible to this direction, allowing for the thickness.

As seen in Figure 2, the turbine according to the invention is mlaced in a body 20 permitting the ejection of shot through the pipe 200. This turbine comprises a series of blades 1 (two being shown) driven in rotation (arrow w) about an axis 21. The blades present a surface '2 for recemtion of the shot 101 to be pro I- jected, which surface 22 extends between an extremity or edge 23 adjacent to;L.-.he axis 21, (edae 1-3 or extremity for the initial reception of the. shot..-c be projected) and an extremity or edge 24 remote from the said axis 21 (edge for the ejection of the shot). The edge 23 is situated at a distance r, from the axis 21, distance r, less than the distance r, separating the edge 24 from the axis 21.

The reception surface presents between its edges 23, 24 a concave and circular profile (radius R).

is The tangent t23 makes an angle a with the tangent t of a cvlinder of revolution about the axis 21 and the radius of which is rj, tangent t in the vicinity of the edge 23. This angle a is advantageously less than 450, thus ensuring an excellent reception (gentle reception).

The reception will be all the better as the angle a approaches 00 (for example less than 15). The tangent t., of the said prof ile in the vicinity of the edge 24 makes an angle V with respect to a radial line-r extending between the axis 21 and the said 25 edge 24. This angle is between 0 and 600. The profile of the vane or of the blade is conceived according to the invention so as to eject the shot with as high a resultant velocity as possible, for a given rotational velocity, preferablv the lowest possible.

In other words, in order for the resultant velocity V.

-, (Figure 4) to be maximal for a fixed tangential velocity Vt (therefore fixed w since Vt = w.r2, with w in radlsec), the angle V (angle V which the ejection edge 24 makes with respect to a radial line T passing through the tom of this edge) is between 0 and 60', this deDending on the type of shot used.

The angle y is fixed by the velocity to be obtained as a function of the rotational velocity of the vanes 1 (N revolutions per minute), but also as a function of the admissible degree of wear of the vanes. It is plain that high angles V can produce highly excessive wear, requiring the use of vanes of very high hard5 ness.

The relative velocity V. combined with the velocity Vt gives the resultant velocity V, When the angle V increases, the relative velocity V. decreases, but the combination c1P the two speeds can give a higher resultant velocity V,, at equal rotational velocity (N revolutions per minute). Depending on the shot projected, this optimum anale varies from 00 to 60. Below or above this value, the combination of the two speeds Vt and V. gives a lower resultant velocity at equal rotational velocity N.

The profile of this vane is of circular curvature, the radius of which is selected depending on the dimensions r, and r2 of the turbine so as to arrive at the angle V required. It is essential to select a circular profile resulting in a better ratio Vx/N for some particular shotblasting applications. In fact, for a small turbine, the gain in velocity V,, for a given rotational velocity is substantial. In fact, for known turbines, it is necessary to rotate at very high-speeds (+ 20%) in order to achieve the same result.

Similarly, in shot-blasting rolling-mill rolls, the tendency is to increase the hardness of the roll surfaces in order better to resist wear. Consequently. shot-blasting of the rolls becomes more and more difficult, or even impossible.

it should be noted that the solution consisting in rotating more quickly in order to attain a higher velocity risks breaking the particles upon entry, during the initial reception. Moreover, increasing the velocity leads to an increase in the unbalance forces proportional to the square of the rotational velocity.

The invention therefore allows these disadvantages to be avoided because it permits substantial speeds VR for lower rotational speeds.

- 8 The design of the turbine according to the invention has made it possible to construct miniature shot-blasting turbine machines, movable manually. The performance of this type of turbine therefore makes it possible to construct shot-blasting machines with a portable turbine but also to construct shot-blasting machines requiring very high projection speeds, such as those used in rolling-mill roll shot-blasting machines. These turbines may equally be used in shot peening, where high projection speeds are often necessary.

Figures 5 and 6 show an embodiment of this type of turbine with four vanes 1, respecting the recommended performance conditions, for a selected type of angular shot.

is The vanes 1 of this embodiment form an integral part of the drive flange 3 (Figures 5, 6). This flange 3 has apertures allowing the passage of bolts 25 for its mounting on a drive shaft 26.

Another embodiment of a vane 1 according to the invention is that found again in Figures 7 and 8, where the hole 4 and the cutaway 5 in the rib 6 serve f or mounting the vane. The initial reception 23 is seen on the active face 22. Another vane disposition is shown in Figures 9 to 11. The active face 22 is indicated therein.

This vane is not provided with a dorsal rib. The two studs 9 serve to mount the vane in the two f langes 3A, 3B, shown partially.

In order to increase the aggressiveness of the projection, it may be useful to f orm a channel 27, the width of which decreases as a function of the increase in the radius r. Another solution is to form a channel, the profile of which in transverse cross-section is slightly curved. This manner of constructing the vane concentrates the shot at the centre, just at the moment of the ejec- tion.

The vanes or blades according to the invention are advantageously constructed in a very hard, anti-wear material, such as in tungsten carbide or in any other more or less effective anti-wear material.

The turbine may be cast in one single piece with the vanes incorporated and in"one single block. It may equally have a different number of vanes, even or odd, for example from 2 to 20, in particular from 4 to 7. of course, it would not be beyond the scope of the invention to construct vanes having an active shape as claimed but whose mode of attachment and/or external shape were different. Only the active face 22 is important in the turbine according to the invention.

Claims

1. Shot-blasting turbine for the high-speed projection of shot, this turbine comprising a series of blades or vanes which are driven in rotation about an axis and a reception surface of which extends between a f irst extremity adjacent to the said axis for the initial reception of shot to be projected and a second extremity remote from the said axis for the ejection of the shot, the said first extremities being situated at a distance from the said axis less than the distance separating a second extremity - from the axis, characterized in that each reception surface presents between its said first and second extremities a concave profile of circular curvature, the tangent of the said profile in the vicin- is ity of the first extremity making an angle a of less than 90 with the tangent, in the vicinity of the said first extremity, to a cylinder of revolution about the axis, the radius of which corresponds to the distance separating the first extremity of the reception surface in question and the said axis, whereas the tangent of the said profile in the vicinity of the second extremity makes an angle V of less than 600 with respect to a radial line extending between the said axis and the said second extremity.

2. Turbine according to Claim 1, characterized in that each reception surface presents between its said first and second extremities a concave and circular profile, the tangent of the said profile, in the vicinity of the f irst extremity, making an angle a of less than 45 with the tangent, in the vicinity of the said first extremity. to a cylinder of revolution about the axis, the radius of which corresponds to the distance separating the first extremity of the reception surface in question and the said axis.

3. Turbine according to Claim 1 or 2, characterized in that each vane is provided with two mounting studs housed in the two turbine flanges.

4. Turbine according to Claim 1 or 2, characterized in that each vane is provided behind its active face with a rib, with hole and cutaway, serving for its mounting.

5. Turbine according to Claim 1 or 2f characterized in that the vanes f orm an integral part of a drive flange.