Title of Invention

DRILL BIT AND METHOD FOR GRINDING A DRILL POINT

Abstract

The invention relates to a drill point (2), having main cutting lips (4a, 4b) which are connected together by a transversal cutting edge (6). A flank (7) which extends into a flute (8) lies adjacent to each main cutting edge. The drill point (2) is ground, in particular, during a continuous three-dimensional grinding process in such a way that the flank (7) forms a continuous curved surface which follows a radius of curvature (R) running from the main cutting lips (4a) in the direction of the flute (8). The continuous grinding process, in comparison to a conventional two-stage process produces an improved drill point geometry which is devoid of edge (16). The edge ; free configuration reduces the mechanical stress during drilling to a minimum.

Full Text

The invention relates to a drill point and to a method for grinding a drill point which has cutting lips which are connected via a chisel edge and which have adjoining them in each case a flank which merges into a flute. Drill points of this type are used, in particular, for twist drills, in which the chips removed by the drill point are removed via helically running flutes of the drill. For this purpose, the drill point and drill are produced in one piece or in two pieces. In the two-piece design, the drill point is produced, in particular, as an exchangeable insert for a drill basic body. The geometric configuration and, in particular, the grinding of the drill point determine to a considerable extent the cutting action of the drill and the mechanical load on the drill, in particular the drill point. The mechanical load during drilling is also determined, inter alia, by the configuration of the region around the chisel edge. To reduce the load, therefore, a thinning of the chisel edge is usually carried out during grinding. The thinning determines, in the region of the drill core, what is known as the rake angle which defines the angle between the face adjoining the chisel edge and the drill longitudinal axis. The face is designated hereafter as the chisel edge face. In particular, the rake angle is determined in that region of the chisel edge which faces away from the cutting lip and where the flank assigned to the cutting lip merges into the flute. A positive rake angle is often desirable in this region. A positive rake angle means, in this case, that the chisel edge face is tilted towards the drill longitudinal axis, so that a kind of overhang is formed. By contrast, where a negative rake angle is concerned, this face is tilted away from the drill axis. In conventional grinding methods with thinning, in a first method step, the cutting lips and the chisel edge and also the flanks adjoining the cutting lips are ground. In a second work step, thinning is then carried out. For this purpose, it is necessary for the grinding wheel provided for grinding to be applied anew. The result of this is that an edge, that is to say a discontinuity, is ground both into the flank and into the chisel edge face. The edge in the chisel edge face is necessarily produced, since, under all circumstances, the situation must be avoided where the grinding wheel reaches as far as the already ground chisel edge during thinning. This edge in the region of the chisel edge causes stress peaks to occur which lead to increased load on the drill point. More recent development trends are towards producing the drill point without grinding by means of a metal injection-moulding method. The object on which the present invention is based is to design a drill point in such a way that the mechanical loads occurring during drilling are kept low. The object is achieved, according to the invention, by means of a drill point which has, in particular, two cutting lips which are connected to one another via a chisel edge and which have adjoining them in each case a flank which merges into a flute, the flank being produced as a surface curved, edge-free, from the cutting lip in the direction of the flute and having a radius of curvature R. A drill point of this type has the essential advantage that, by virtue of the surface curved, edge-free, and having the radius of curvature R, that is to say by virtue of an offset-free run of the surface, the load on the drill point during drilling is low. In particular, no stress peaks occur in the region of the chisel edge face, such as occur in the case of conventionally ground drill points. Further preferred embodiments of the drill point are recorded in the subclaims. The drill point is preferably a ground drill point. Alternatively, the described geometry of the drill point may also be achieved, for example, by means of a metal injection-moulding method. In a particularly advantageous refinement, the drill point is produced as an exchangeable insert for a drill basic body. A two-part drill of this type, consisting of a drill point and a drill basic body, has the essential advantage that the drill point susceptible to wear can be exchanged in a simple way. The drill basic body is exposed, as a rule, to substantially lower wear, so that its useful life exceeds that of the drill point by a multiple. By the drill point being produced as an exchangeable insert, therefore, in particular, the operating costs are markedly reduced. Not least, there may be provision, in this respect, for producing the drill basic body from a more cost-effective and consequently usually softer material than the drill point. Furthermore, the object is achieved, according to the invention, by means of a method for grinding a drill point which has, in particular, two cutting lips which are connected via a chisel edge and which have adjoining them in each case a flank which merges into a flute, a grinding wheel used for grinding and the drill point being guided relative to one another in a continuous grinding operation, in such a way that the flank is produced as a surface curved from the cutting lip in the direction of the flute and having a radius of curvature. The grinding wheel and the drill point are, therefore, in this case guided relative to one another in a complex three-dimensional grinding operation, in such a way that the drill point is ground in the desired way, without two grinding operations being necessary. In particular, by virtue of the continuous grinding operation, no edges occur in the region of the flank and of the chisel edge face, said edges necessarily being produced in the case of a two-stage grinding operation. As a result of the three-dimensional guidance of the drill point and the grinding wheel, therefore, the two grinding steps conventional hitherto are combined in one grinding step. This is manifested, not least, in the curvature of the flank. On account of the offset-free and edge-free run of the ground faces of the drill point, the load on the drill point during drilling is kept low. For as low a load on the drill point as possible, the method is preferably carried out in such a way that a radius of curvature of between 0.05 and 0.5 times the drill diameter is obtained. To produce the curved flank, the grinding wheel comprises a main grinding face which is pivoted relative to the drill point through a pivot angle. This pivoting movement may be executed either by the drill point or by the grinding face or by both together. During this pivoting movement, the angle, designated as the pivot angle, between the surface normal of the main grinding face and the longitudinal axis of the drill point is reduced. To produce a suitable drill-point geometry, the drill point is preferably first rotated about its longitudinal axis up to an angle of rotation, and only subsequently pivoting through the pivot angle takes place. What is achieved thereby is that the flank, what is known as the main flank, directly adjoining the cutting lip first runs obliquely and is subsequently curved increasingly in the direction of the flute. For as homogeneous a design of the curved surface as possible, during pivoting through the pivot angle a the drill point is simultaneously further rotated up to a predetermined final angle of rotation. In a particularly expedient version, a secondary grinding face of the grinding wheel and the drill point are pivoted relative to one another through a rake angle for the thinning of said drill point in the region of the chisel edge. This secondary grinding face is contiguous to the main grinding face of the grinding wheel, and, with it, the chisel edge face, that is to say the transition from chisel edge to flank, is ground. The run of this face in relation to the longitudinal axis of the drill point in this case specifies what is known as the rake angle (chisel edge rake angle) . To form the rake angle, the complete grinding wheel is pivoted with respect to the longitudinal axis of the drill point. Preferably, the pivoting movements through the pivot angle and through the rake angle are superposed on one another. The grinding wheel is therefore pivoted simultaneously through two angles. The pivoting movement through the pivot anqle takes olace in this case about a pivot axis which runs approximately radially outwards from the chisel edge, and the pivoting movement through the rake angle takes place about a pivot axis which runs approximately tangentially to the chisel edge. Superposing these two pivoting movements ensures that, on the one hand, suitable thinning is carried out and, on the other hand, the ground faces merge homogeneously into one another. In particular, the chisel edge face merges homogeneously, that is to say offset-free and edge-free, into the flank. Preferably, the rake angle is set between a positive rake angle of +5° and a negative rake angle of -5°. The advantage of the method described is to be seen, in particular, in the formation of a positive rake angle, since the latter can easily be achieved by means of the method described. To produce a suitable drill-point geometry, the pivot angle is between 30° and 60° and amounts, in particular, to about 50°. The angle of rotation is preferably between 60% and 90% and amounts, in particular, to about 80% of the final angle of rotation. The latter is typically in a range between 90° and 140°. In order to grind the chisel edge in a suitable way, in a preferred version the grinding wheel projects beyond the drill centre at the commencement of the grinding operation, so that the grinding wheel assumes an above-centre grinding position. The drill point and the grinding wheel are subsequently guided into a below-centre grinding position, in which the grinding wheel terminates in front of the drill centre. In the below-centre grinding position, the grinding of the flank and thinning then take place. The advantages listed with regard to the method and the particular embodiments can be transferred accordingly to the drill point. An exemplary embodiment of the invention is explained in more detail below with reference to the figures. Of the figures, in each case in diagrammatic illustrations, Fig. 1 shows a drill point ground according to a conventional method, Fig. 2 shows a drill point which is ground by the method according to the invention, Fig. 3 shows a drill and a grinding wheel in an initial position at the commencement of the grinding operation in a perspective illustration, Fig. 4 shows the drill and the grinding wheel in a middle position during the grinding operation, likewise in a perspective illustration, Fig. 5 shows the drill and the grinding wheel in a final position after the grinding operation, likewise in a perspective illustration, Fig. 6 shows a side view of the drill and of the grinding wheel, Fig. 7 shows a side view, rotated through 90° in relation to Fig. 6, of the drill and of the grinding wheel, and Fig. 8 shows a drill with an exchangeable drill point. In the figures, identically acting parts are given the same reference symbol in each case. In Figures 1 and 2, a drill point 2 of a twist drill 3, said drill point being ground according to a conventional method (Fig. 1), and a drill point ground according to the novel method (Fig. 2) are placed in relation to one another. The drill point 2 has two cutting lips 4a, 4b which are connected to one another via a chisel edge 6 of approximately S-shaped design. The cutting lips 4a, 4b and the chisel edge 6 are illustrated in the figures by a broader line thickness for the sake of greater clarity. The cutter formed by the cutting lips 4a, 4b and chisel edge 6 extends over the entire drill point 2. The drill point 2 is designed mirror-symmetrically. The drill point 2 is explained below with reference to one of the two mirror-symmetrical sides, specifically starting from the cutting lip 4a. The latter has adjoining it a flank 7 which extends as far as a flute 8. The flute 8 commences even in the drill point 2 and runs helically in the flute region 9, adjoining the drill point 2, of the drill 3. The flank 7 adjoining the cutting lip 4 is designed essentially in the manner of a conical face. A face, designated as a chisel edge face 10, likewise extends from the chisel edge 6 to the flute 8. The chisel edge face 10 and the flank 7 merge into one another. During what is known as the thinning of the drill point 2, in particular, the chisel edge face 10 is ground. In this case, the angular relation between this face 10 and the longitudinal axis 14 of the drill point 2 is set. The corresponding angle is designated as the rake angle 8 (cf. in this respect, in particular Fig. 7). In the conventional grinding method, for thinning, the grinding wheel is applied anew in a second method step and is led up to the chisel edge face 10, in particular in the region in which the chisel edge 6 merges into the second cutting lip 4b. In order to prevent contact of the grinding wheel with the already ground chisel edge 6 and the cutting lip 4b, a particular safety clearance must be maintained in relation to these two cutters (4b, 6). This is manifested, in the ground drill point 2, in that the chisel edge face 10 has a kink or an edge 16. This extends into the flank 7. The latter therefore bends towards the flute 8 at the edge 16. Undesirably high mechanical loads occur during drilling at this edge 16, in particular in the region of the chisel edge face 10. By virtue of the continuous three-dimensional grinding operation according to the novel grinding method, such an edge 16 is avoided in the drill point 2 according to Fig. 2. Instead, the chisel edge face 10 merges homogeneously into the flank 7 and both extend, kink-free and edge-free, as far as the flute 8. Moreover, in addition to the edge-free run, it is characteristic of the drill point 2 ground according to the novel method that the flank 7 is curved from the cutting lip 4a towards the flute 8 and has a radius of curvature R. This is preferably between 0.05 and 0.5 times the drill diameter D. To illustrate the individual grinding regions, the flank 7 is subdivided into two differently hatched subregions 7A and 7B, the subregion 7A indicating essentially the curved region of the flank 7. Furthermore, the chisel edge face 10, as the third grinding region, is likewise illustrated hatched. All three grinding regions (10, 7A, 7B) are ground in a continuous grinding operation and merge homogeneously into one another. The outer line 18, running on the circumference of the drill point 2, of the flank 7 forms with the latter, when projected onto the longitudinal axis 14, in the region of the transition to the flute 8, a pivot angle a which is preferably between 30° and 60° (for the definition of the pivot angle a, cf. also, in particular, Figures 6 and 7). The novel grinding method is explained in more detail below with reference to Figures 3 to 5, in which the relative position between a grinding wheel 20 and the drill point 2 is illustrated in each case in a perspective illustration and in different grinding positions. For the three-dimensional grinding operation described below, the relative movement between the drill point 2 and the grinding wheel 20 is critical. For the sake of simplicity, the grinding operation is expressed either by the movement of the drill point 2 or by the movement of the grinding wheel 20. It goes without saying that the respective movement may also be executed accordingly by the other part in each case. For the sake of greater clarity, in Figures 3 to 5, the grinding wheel 20 is illustrated in each case only partially and by broken lines. According to the initial position illustrated in Fig. 3, the longitudinal axis 14 of the drill point 2 is oriented at an angle a" to a mid-axis 22 of the grinding wheel 20, said angle amounting to 90° at the commencement of grinding. The grinding wheel 20 has a margin with a trapezoidal geometry, as seen in cross section, one outer side of the trapezium being produced as a main grinding face 24 and the end face adjoining this side face being produced as a secondary grinding face 26. The main grinding face 24 merges into the secondary grinding face 26 to form a curvature. This curvature defines essentially a rounded transition between the chisel edge face 10 and the flank 7. The radial extent of the main grinding wheel 26 is greater than the drill radius, so that it completely covers the flank 7. This annular grinding body is seated with its trapezium base on a disc-shaped carrier 28 and forms with the latter the grinding wheel 20. The grinding wheel 20 is clamped rotatably in a suitable way by means of the carrier 28. The longitudinal axis 14 is depicted as running through the tip of the drill point 2, that is to say the drill centre 27. It may be gathered from Fig. 3 that the main grinding face 24 projects beyond the drill centre 27 in the region of the chisel edge 6. The grinding wheel 20 is therefore applied, above-centre, at the commencement of the grinding operation. In the course of the grinding operation, the drill 3 is then guided along an X-axis into a below-centre position. The above-centre initial position serves for grinding the chisel edge 6 which, at the commencement of the grinding operation, is held approximately perpendicularly to the circumferential line 29 of the secondary grinding face 26. At the commencement of the grinding operation, the cutting lip 4a is ground. The drill is then rotated about the longitudinal axis 14 through an angle of rotation P, so that the flank 7 adjoining the cutting lip 4a is ground. The cutting lip 4a and the flank 7 fall outwards from the drill centre 27. The cutting lip 4a and a radial component of the flank 7 are therefore inclined at an angle s to an imaginary cross-sectional plane 34 of the drill point 2 (cf., in this respect, also Fig. 6). When the longitudinal axis 14 is oriented perpendicularly to the mid-axis 22, this angle e is determined by the trapezium angle e between the main grinding face 24 and the normal to the trapezium base. In addition to the rotational movement through the angle of rotation P and the initial displacement along the X-axis, an advance of the drill in the direction of the longitudinal axis 14 in relation to the grinding wheel 20 takes place, so that the flank 7, specifically its tangential component, runs at an angle X obliquely to the imaginary cross-sectional plane 34 of the drill 3. Thus, starting from the cutting lip 4a, the outer line 18 runs obliquely downwards in the direction of the flute 8 (cf. Fig. 6). In the middle position according to Fig. 4, the drill point 2 is in a below-centre grinding position in relation to the grinding wheel 20, that is to say the chisel edge 6 lies next to the secondary grinding face 26. The circumferential line 29 of the latter now runs approximately tangentially to the chisel edge 6. The grinding operation up to the middle position illustrated corresponds essentially to a conventional grinding method. The novel method is distinguished in that, starting from the middle position, the drill point 2 is pivoted, on the one hand, with respect to the main grinding face 24 and, on the other hand, with respect to the secondary grinding face 26. Pivoting with respect to the main grinding face 24 takes place through the pivot angle a about a main axis 30, and pivoting with respect to the secondary grinding face 26 takes place through the rake angle 5 about a secondary axis 32, as may be gathered from Figures 6 and 7. By pivoting through the pivot angle a, the angle a", associated with the pivot angle a, between the longitudinal axis 14 and the mid-axis 22 is reduced. This may be gathered from Fig. 5, from which it becomes clear that the drill 3 is now oriented at an acute angle a" to the mid-axis 22 after it was originally oriented perpendicularly to the mid-axis 22 at the commencement of the grinding operation. Figures 6 and 7 serve for illustrating the pivoting movement which is carried out between the drill 3 and the grinding wheel 20 at the transition from the middle position into the final position. For the sake of greater clarity, the grinding wheel 20 is again illustrated by broken lines and only partially in a diagrammatic side view. Fig. 6 shows in this case a side view, in which the viewing direction is essentially perpendicular to the chisel edge 6, and Fig. 7 shows a side view in which the viewing direction is approximately in the longitudinal direction of the chisel edge 6. It may be gathered from Fig. 6 that the cutting lip 4a runs at the angle 8 to a imaginary cross-sectional plane 34 of the drill point 2. It may be gathered, furthermore, that, starting from the cutting lip 4a, the circumferential line 18 of the flank 7 first runs obliquely at the angle X in the direction of the flute 8 and then has a curvature with the radius of curvature R. To form this curvature, the grinding wheel 20 is pivoted with its main grinding face 24 about the main axis 30 through the pivot angle a. This is defined as the angle between the longitudinal axis 14 and the tangential component of the main grinding face 24. Preferably, at the same time, the grinding wheel 20 is pivoted about the secondary axis 32 through the rake angle 6 so as to form a rake angle in the region of the chisel edge 6. Preferably, a positive rake angle 5 of up to +5° is set for the chisel edge face 10. In this case, the chisel edge face 10 is ground by means of the secondary grinding face 26, in such a way that it forms a kind of overhang, as may be gathered from Fig. 7. The rake angle 8 fixes the angle between the secondary grinding face 26 and the longitudinal axis 14. Owing to the fixed angular relation between the two grinding faces 24, 26, the rake angle 8 is determined by the orientation of the radial component of the main grinding face 24 relative to the longitudinal axis 14. To summarize, the preferred grinding operation can be divided into the following steps: 1. Commencement of the grinding operation in an above-centre grinding position with an angle of rotation p, the longitudinal axis 14 being oriented perpendicularly to the mid-axis 22 (initial position, Fig. 3). 2. Movement of the drill 3 into a below-centre grinding position along the X-axis. At the same time, an advance in the direction of the longitudinal axis 14 takes place, and also a rotational movement about the latter up to an angle of rotation P of about 80% of the final angle, of rotation y. In this case, at the same time, a translational displacement of the drill along a Y-axis running perpendicularly to the X-axis may take place. The X-axis and the mid-axis 24 run parallel. (Middle position, Fig. 4) At the transition from the initial position into the middle position, therefore, 3 movement components are superposed. 3. Further rotation of the drill 3 up to the final angle y, so that the drill 3 executes approximately a rotation of 120°, starting from the initial position. Furthermore, at the same time, the advance in the direction of the longitudinal axis 14 takes place, and also the movement along the X-axis, and, in addition, pivoting through the pivot angle a and through the rake angle 8 take place. Overall, therefore, in the last work step, 5 movement components are superposed in order to reach the final position. Pivoting through the rake angle 5 according to point 3 is optional in this case. The formation of a rake angle 5 depends on the intended use for which the drill 3 is provided. The method makes it possible to set the rake angle 5 simply and in a very flexible way. The critical advantage of the method is to be seen in that the grinding operation is carried out in a continuous process, and a second application of the grinding wheel, with the accompanying edge-like transitions necessarily occurring in the region of the flank 7 and of the chisel edge face 10, is avoided. According to Fig. 8, the drill 3 is preferably constructed in two parts and, for this purpose, has a drill basic body 36 having, on its end face, a recess 38, into which the correspondingly shaped drill point 2 can be inserted, in particular exchangeably. The drill point 2 is held in the drill basic body 36, for example, by means of a clamping force which is exerted by two legs 40. Alternatively or additionally, the drill point 2 is fixed in the basic body 36 by locking which is not illustrated. The flute 8 running in the drill basic body 36 extends into the drill point 2. This configuration with an exchangeable drill point 2 makes it possible to keep the operating costs for the drilling tool low, since the structural part which is exposed to the highest mechanical loads is produced as a replacement part. List of reference symbols. 2 Drill point 4a, 4b Cutting lips 6 Chisel edge 7 Flank 8 Flute 10 Face 9 Flute region 14 Longitudinal axis 16 Edge 18 Outer line 20 Grinding wheel 22 Mid-axis 24 Main grinding face 26 Secondary grinding face 27 Drill centre 28 Carrier 29 Circumferential line 30 Main axis 32 Secondary axis 34 Cross-sectional plane 36 Basic body 38 Recess WE CLAIM : 1. Drill point (2), which has main cutting lips (4a, 4b) which are connected to one another via a chisel edge (6) and adjoining which in each case is a flank (7) which merges into a flute (8), characterized in that the flank (7) has two sub regions (7A, 7B) which merge into one another homogeneously and without edges, the sub region (7A) which runs to the flute (8) being formed as a curved surface having a radius of curvature (R), and in that the flank (7), at the transition to the flute (8), forms a pivot angle (a) with the longitudinal axis (14), this pivot angle (a) is between 30° and 60°. 2. Drill point (2) as claimed in claim 1, wherein the radius of curvature (R) is between 0.05 times and 0.5 times the drill diameter (D). 3. Drill point (2) as claimed in claim 1 or 2, wherein the pivot angle (a) is about 50° 4. Drill point (2) as claimed in any one of claims 1 to 3, wherein the rake angle (8) is between +5° and -5°. 5. Drill point (2) as claimed in any one of claims 1 to 4, wherein it is produced as an interchangeable insert for a drill basic body (36). 6. Method of grinding a drill point (2) which has main cutting lips (4a, 4b) which are connected via a chisel edge (6) and adjoining which in each case is a flank (7) which merges into a flute (8), characterized in that a grinding wheel (20) and the drill point (2) are guided in a continuous grinding operation relative to one another in such a way that the flank (7) is formed such as to run from the main cutting lips (4a, 4b) to the flute (8) without edges and in one sub region (7A) as a curved surface having a radius of curvature (R), by the longitudinal axis (14) of the drill point and a mid-axis (22) of the grinding wheel (20) being pivoted relative to one another by a pivot angle (a). 7. Method as claimed in claim 6, wherein the radius of curvature (R) is between 0.05 times and 0.5 times the drill diameter (D). 8. Method as claimed in claim 6 or 7, wherein the drill point (2) is first of all rotated about its longitudinal axis (14) up to an angle of rotation (P) and then the pivoting by the pivot angle (a) is effected 9. Method as claimed in claim 8, wherein the drill point (2) is rotated further about its longitudinal axis (14) up to a final angle of rotation (y) during the pivoting. 10. Method as claimed in claims 6 to 9, wherein a secondary grinding surface (26) of the grinding wheel (20) and the drill point (2) are pivoted relative to one another by a rake angle (5) in the region of the chisel edge (6) in order to thin the drill point (2). 11. Method as claimed in any one of claims 6 to 10, wherein the pivoting movements by the pivot angle (a) and bv the rake anele (8) are superimposed. 12. Method as claimed in any one of claims 10 or 11, wherein the rake angle (8) is between +5° and -5°. 13. Method as claimed in any one of claims 6 to 12, wherein the pivot angle (a) is between 30° and 60°, and in particular 50°. 14. Method as claimed in any one of claims 8 to 13, wherein the angle of rotation (P) is between 60% and 90%, and in particular 80%, of the final angle of rotation (y). 15. Method as claimed in any one of claims 6 to 14, wherein at the start of the grinding operation, the grinding wheel (20) projects beyond the drill centre (27), so that there is an above-centre grinding position, and in that subsequently, the drill point (2) and the grinding wheel (20) are guided into a below-centre grinding position, in which the grinding wheel ends in front of the drill centre

Documents:

in-pct-2002-0719-che abstract-duplicate.pdf

in-pct-2002-0719-che abstract.jpg

in-pct-2002-0719-che abstract.pdf

in-pct-2002-0719-che claims-duplicate.pdf

in-pct-2002-0719-che claims.pdf

in-pct-2002-0719-che correspondence-others.pdf

in-pct-2002-0719-che correspondence-po.pdf

in-pct-2002-0719-che description (complete)-duplicate.pdf

in-pct-2002-0719-che description (complete).pdf

in-pct-2002-0719-che drawings.pdf

in-pct-2002-0719-che form-1.pdf

in-pct-2002-0719-che form-19.pdf

in-pct-2002-0719-che form-26.pdf

in-pct-2002-0719-che form-3.pdf

in-pct-2002-0719-che form-5.pdf

in-pct-2002-0719-che others.pdf

in-pct-2002-0719-che pct.pdf

in-pct-2002-0719-che petition.pdf

IN-PCT-2002-719-CHE CORRESPONDENCE OTHERS 27-05-2011.pdf

IN-PCT-2002-719-CHE FORM-13 27-05-2011.pdf

IN-PCT-2002-719-CHE POWER OF ATTORNEY 27-05-2011.pdf