Positioning of a spindle with micrometric forwarding control and tilting of its rotation axis

Abstract

A positioning of a spindle with micrometric forwarding control and tilting of its rotation axis includes a spindle shaft rotatingly supported inside rotatable supports, wherein the rotatable supports include two spherical elements having housings which are eccentric with respect to the rotation axis that join the centers of the spheres, and wherein the two spherical elements are positioned in a cylindrical housing having at least two parts, and wherein two rotation elements are connected to the two spherical elements and cause their independent rotation.

Claims

1. A positioning device of a spindle with micrometric forwarding control and tilting of a rotation axis of the spindle, the device comprising a spindle shaft (11) rotatingly supported inside at least two rotatable supports, wherein said at least two rotatable supports comprise two spherical elements (13,14) provided with respective housings (12) eccentric with respect to an axis (99) of said spherical elements (13,14) and passing through a center of said spherical elements, said two spherical elements (13,14) being positioned in a housing having at least two parts (17,17; or 19,20), further comprising two rotation elements (23,24) connected to the two spherical elements (13,14) for causing an independent rotation.

2. The positioning device of a spindle according to claim 1, wherein said spherical elements (13,14) comprise spheres each having a seat (12) for the spindle shaft (11), said seat being a pass-through hole eccentric with respect to said spherical elements.

3. The positioning device of a spindle according to claim 1 wherein said housing having at least two parts (17,17; or 19,20) is positioned in a wheelhead, a cartridge, or a shaped sleeve (18) which is adapted to be installed on a wheelhead.

4. The positioning device of a spindle according to claim 1, wherein said spindle shaft (11) and said spherical elements (13,14) are coupled with hydrostatic hydrodynamic, rolling, or sliding bearings.

5. The positioning device of a spindle according to claim 1, where each of said spherical elements (13,14) is positioned the housings, each of the housings having two parts (17,17; or 19,20).

6. The positioning device of a spindle according to claim 5, wherein said two parts (17,17) of each of the housings are, inserted in a spindle cartridge (18) or in a wheelhead.

7. The positioning device of a spindle according to claim 1, wherein each of said housings of said two spherical elements (13,14) comprises a single central housing (19) facing sides of said spherical elements (13,14) and two end side-housings (20).

8. The positioning device of a spindle according to claim 1, wherein said two rotation elements are two levers (23, 24).

9. The positioning device of a spindle according to claim 8, wherein said two levers (23,24) extend into further levers (29,30) activated by respective linear movement systems (u1,u2).

10. The positioning device of a spindle according to claim 9, wherein said two levers (23,24) extend into said further levers (29,30) by interposing two ball joints (27,28) and wherein said further levers (29,30) are connected to said linear movement systems (u1,u2) by interposing further ball joints (31,32).

11. The positioning device of a spindle according to claim 9, wherein said linear movement systems (u1,u2) comprise screw controls driven by electric motors.

12. The positioning device of a spindle according to claim 9, wherein said two linear movement systems (u1,u2) consist of linear motors.

13. The positioning device of a spindle according to claim 1, wherein said two rotation elements are torque motors.

14. The positioning device of a spindle according to claim 1, wherein said spindle shaft (11) and at least one of the two spherical elements (13,14) are processed so as to act as a thrust or house a thrusting member (21) for opposing forces acting along an axis of the spindle.

Description

[0079] The structural and functional characteristics of the present invention and its advantages with respect to the known art will appear even more evident from the following description, referring to the enclosed schematic drawings, which, in addition to elements and characteristics of the known art, also show an embodiment of the invention. In the drawings:

[0080] FIG. 1 is a schematic perspective view illustrating the grinding process;

[0081] FIGS. 2 to 6 show various types of sections of rolling mills using different rolling cylinders;

[0082] FIG. 7 shows rolling cylinders having different surface profiles;

[0083] FIG. 8 shows the ideal position of a grinding wheel for the grinding of a cylinder with any non-straight profile;

[0084] FIG. 9 shows the position of a grinding wheel which causes the gouging phenomenon during the grinding of a cylinder having any non-straight profile;

[0085] FIG. 10 is a schematic perspective view of a cylindrical peripheral grinding machine for the outside;

[0086] FIG. 11 is a schematic detail of a first known solution in which there is the micrometric positioning of the grinding wheel with only one axis X, i.e. with one degree of freedom;

[0087] FIG. 12 is a schematic detail of another known solution in which there is the micrometric positioning of the grinding wheel with an axis X and an axis U, i.e. with two degrees of freedom;

[0088] FIG. 13 is a schematic detail of a second known solution in which there is the micrometric positioning of the grinding wheel with two degrees of freedom;

[0089] FIG. 14 is a schematic view of a known solution in which there is the micrometric positioning of the grinding wheel with an axis X, an axis U and an axis B, i.e. with three degrees of freedom;

[0090] FIGS. 15 and 16 are schematic views of known solutions similar to those of FIG. 14 with a rotation centre of the head rotating in different positions;

[0091] FIG. 17 shows a rotation application scheme of a wheelhead with a tilted axis in the tilt infeed version;

[0092] FIG. 18 shows the solution illustrated and object of U.S. Pat. No. 6,234,885 B1;

[0093] FIG. 19 illustrates a sectional view of a positioning of a spindle with a micrometric forwarding and tilting command of the axis according to the present invention in a first embodiment thereof;

[0094] FIG. 20 illustrates a sectional view of a positioning of a spindle similar to that of FIG. 19 in a second embodiment;

[0095] FIG. 21 shows an embodiment example of the movement commands of the actuation levers;

[0096] FIGS. 22a and 22b show two three-dimensional diagrams in which, in the first, the dependent variable U1 corresponding to the first actuation of the mechanism is associated with each pair of independent variables (U,), in the second, the second dependent variable U2, corresponding to the second actuation, is associated with each pair (U,);

[0097] FIG. 23 shows a diagram which illustrates the operating range of the kinematic mechanism, i.e. of the positioning of the spindle according to the invention. As the mechanism in question has two degrees of freedom, in order to characterize the operating range, the limits that the independent variables of the system can have, must be defined. The diagram shows, in the abscissa, the forwarding of the grinding wheel-cylinder contact point (independent variable U) and, in the ordinate, the rotation angle of the spindle axis on the horizontal plane (independent variable a); the mechanism, object of the present invention, allows all the pairs (U,) enclosed within the segments indicated in the figure, to be obtained;

[0098] FIGS. 24 and 25 are schematic sectional views that show how the micrometric forwarding of the grinding-wheel centre P according to the present invention, is obtained;

[0099] FIG. 26 shows a schematic view from above of what is shown in FIG. 21, with particular respect to the actuation levers for obtaining the tilting of the spindle and shifting of the grinding-wheel centre;

[0100] FIGS. 27a and 27b and 28a and 28b respectively show in a view from above and in a raised side view, what is shown in FIG. 21 in different operational positions in order to illustrate the characteristics and functioning more clearly;

[0101] FIG. 29 represents a diagram which shows the forwarding required by the grinding-wheel centre P (independent variable U) for obtaining a certain profile;

[0102] FIG. 30 is the same as FIG. 23 in which, a polar diagram has been superimposed over the operating range, which represents the combination of the pairs of values (U,) for obtaining the profile of FIG. 29. The profile of FIG. 29 can evidently be formed by the mechanism, as the polar diagram is completely contained in the area of use of the same mechanism.

[0103] With reference to FIG. 19, this illustrates an arrangement of the spindle with a micrometric forwarding and tilting command of the axis according to the present invention in one of its embodiments.

[0104] The arrangement of FIG. 19 shows a mechanism that is composed of a spindle 11, housed and rotating in cylindrical seats 12 respectively formed in the body of two spherical elements 13, 14. The two seats 12 are formed with a suitable eccentricity between an axis 15 of the spindle 11 and an axis 99 passing through the centres 16 of each of the spherical elements 13, 14. In particular, these elements 13, 14 consist of portions of spheres, in each of which the seat 12 of the spindle 11 is a pass-through and eccentric hole with respect to the centre of the spherical element.

[0105] The coupling between the spindle 11 and the spherical elements 13, 14 can be effected using the normal techniques adopted in this field, i.e. by means of hydrostatic or hydrodynamic or rolling bearings.

[0106] Each spherical element 13, 14 is, in turn, positioned in a suitable housing which, in the construction form proposed, is composed of two parts, or half-bodies 17 and 17 for allowing the assembly. Also in this case, the coupling between the spherical elements and relative seats can be easily obtained with the techniques mentioned above. The two half-bodies 17 and 17 are housed either directly in a wheelhead (TPM), or in a cartridge or shaped sleeve 18 that can be easily installed on a TPM.

[0107] This solution of FIG. 19 can obviously be alternatively modified by integrating the two internal half-bodies 17 and 17 in the body of the TPM or cartridge. In this way, composite housings 19 and 20 are obtained without modifying the concept of the invention, as shown, for example, in FIG. 20.

[0108] Furthermore, with reference to both FIGS. 19 and 20, the spindle 11 and one of the two spherical elements, for example that indicated with 13, can be processed so as to act as thrust bearings or receive a thrust bearing 21, for opposing the forces acting along the axis of the spindle.

[0109] The spindle 11 can be rotated according to the classical motor with pulley 22 scheme (as represented in FIGS. 19 and 20) or different solutions can be equally used. A motor-spindle can be used, for example (with the motor mounted directly on the spindle cantilevered with respect to the bearings and on the opposite side to the grinding wheel), or using an electro-spindle, with the motor housed between the two spherical joints (neither of these embodiments are shown).

[0110] The arrangement of the present invention is completed by two control means, in the example consisting of levers 23 and 24 which are connected, or in any case extend from the two spherical elements 13 and 14 and allow the desired rotations to be effected by the above-mentioned elements. The two control means, i.e. the two levers 23 and 24, are such as to cause an independent rotation of each of the two spherical elements 13 and 14. In an alternative embodiment, the rotation means can be torque motors or similar means.

[0111] As an embodiment but non-limiting choice, the rotation of spherical elements 13, 14 is regulated with the system represented in FIG. 21.

[0112] The levers 23, 24, integral with the spherical joints 13, 14, positioned in respective housings 17, 17, are in turn constrained, by means of two ball joints, schematized in 27, 28, to a pair of connecting rods 29, 30. This pair of connecting rods 29, 30, through a second stage of ball joints 31, 32, is activated with respective linear movement systems schematized with u1 and u2, which effect the movements defined above as dependent variables U1 and U2, of a system with two degrees of freedom.

[0113] The mechanism is in fact as such, as, as many pairs of positions of the control levers 23 and 24 univocally correspond to each pair of independent variables (U, ), and consequently pairs of the above-mentioned coordinates U1 and U2.

[0114] In order to control the variables (U, ) and allow the applicability of the present kinematic system in a tool machine, in addition to knowing its limits and possibilities of improvement, it is crucial to solve the equations that govern its physical behaviour. In this respect, the writing of non-linear equations and their solution by numerical integration, through suitable software, allows the mathematical solution of the kinematic mechanism to be obtained, by univocally linking the two independent variables (U, ) with the dependent variables (U1, U2), as shown in the diagrams of FIGS. 22a and 22b.

[0115] This type of solution allows the dimensions and geometrical characteristics of the components used to be rationally and optimally selected and also to know and define the functioning limits of the kinematic mechanism itself. If the limits of the variables U1 and U2 are set so as to allow an oscillation of the levers 23, 24 of about +/20 with respect to its own vertical axis, a diagram of the type shown in FIG. 23 is obtained, in which the area enclosed by the segments represents the combination of the values admissible for the independent variables (U, ), compatibly with the kinematic constraints of the system itself. It should be pointed out, however, that by varying the dimensions of the components, the length of the various levers, the distance between eccentric and centre of the spherical elements, and by changing the maximum rotation angle of the spherical elements, said diagram can be regulated and adapted to the most diverse needs, extending the operating limits of the system itself.

[0116] For a clearer understanding of the functioning of the mechanism, some particularly significant situations are described hereunder. Let us begin by imagining that the grinding-wheel centre P is to be forwarded by a quantity U, according to the micrometric eccentric command principle previously described (or Tilt Infeed command), maintaining, however, the rotation axis of the grinding wheel parallel to the axis of the cylinder: one starts with the commands of the levers 23, 24 arranged so that the two coordinates U1 and U2 are identical, as indicated in FIG. 24. Both of these are then increased by the same amount as represented in FIG. 25, obtaining a translation of the spindle shaft 11 and a consequent forwarding of the grinding wheel-piece contact P in the direction X by a desired amount U and with a direction complying with the movement imparted to the two axes U1 and U2, effecting in fact a micrometric forwarding.

[0117] In order to subsequently also obtain, in addition to the variation U in the position of the grinding-wheel centre P along the direction X, the variation in the angle of the spindle , one should proceed as shown in FIG. 26.

[0118] By activating, the commands u1 and u2 and, consequently rotating the control levers 23 and 24, for example according to the directions 25 and 26, independently with respect to each other (obviously within the limits of their run), not only will a variation in the position of the grinding-wheel centre P be obtained (first degree of freedom U), but also the tilting of the axis 15 of the spindle shaft 11 and consequently of the grinding wheel 50, thus obtaining the second degree of freedom .

[0119] It is also possible to tilt the axis of the grinding wheel, without shifting the contact point P with respect, for example, to a starting situation analogous to that indicated in FIG. 24, by regulating the levers 23 and 24 under the conditions specified in FIGS. 27a and 27b (anticlockwise rotation) and in FIGS. 28a and 28b (clockwise rotation). In both examples, in order to obtain the desired result, U1 must be increased, except for the direction, to a greater degree with respect to U2. In order to know the exact value that the variables U1 and U2 must have, it is obviously sufficient to refer to the diagrams represented in FIGS. 22a and 22b.

[0120] In short, by combining and controlling the movements described above with suitable actuations, both the position of the grinding-wheel centre P and the tilting of the grinding wheel itself 50 can be regulated, thus allowing the geometries of cylinders for rolling mills presented in FIG. 7 for illustrative purposes, to be obtained.

[0121] Finally, let us examine a practical case considering a common back-up roll cylinder for CRM applications. Representing in FIG. 29 the required forwarding of the grinding-wheel centre P with respect to the condition 0 (ordinate null), in relation to the position of the grinding-wheel trolley with respect to the plane of the cylinder itself, and remembering that the tangent of the grinding-wheel angle must always be equal to the derivative of the profile itself, the function (U, ) that represents this profile in polar coordinates, is represented in FIG. 30.

[0122] It can be clearly observed how the operating points of the present spindle (indicated by the central curved section) are extremely far from the kinematic limits previously defined and already shown in FIG. 23.

[0123] It will therefore be possible to obtain profiles that are much more complex than that considered herein, therefore operating with greater angles and fully satisfying market requirements, competitively from both an economic and technological point of view.

[0124] In short, the problems of the prior art have been solved through the solution proposed according to the present invention. In this respect, the following improvements can be listed with respect to the state of the art: [0125] the number of bearings and couplings (both axial and radial) is reduced with respect to what is proposed in U.S. Pat. No. 6,234,885 B1, improving the efficiency, the rigidity, the project simplicity and the precision of the system itself; [0126] the frequencies introduced by the spherical joints fall outside the range of frequencies typical of grinding processing, without, however, negatively influencing the process itself; [0127] it is possible to increase the tilting angles of the grinding wheel, until values higher than the present market solutions are reached, without creating, for example, problems of encumbrance typical of rotating heads; [0128] large reduction ratios can be selected as desired, by varying the geometry of the levers and position of the eccentric, thus allowing a facilitated control and repositioning of the system; [0129] it is possible to operate with the grinding-wheel centre P as rotation centre for variable grinding-wheel angle ranges in relation to the position required by the eccentric; [0130] a competitive solution has been obtained from both a technological and economic point of view.

[0131] An accurate mathematical modeling makes it possible to easily pass from the specific variables of the profile of the cylinder to be processed (U, ) to the control variables (U1, U2). This model allows, if necessary, the geometry of the mechanism to be re-parameterized in order to satisfy specific requirements.

[0132] The objective mentioned in the preamble of the description has therefore been achieved.

[0133] The protection scope is defined by the enclosed claims.