WO2011064800A1

WO2011064800A1 - Moving portal for a machine tool or a measuring machine

Info

Publication number: WO2011064800A1
Application number: PCT/IT2009/000536
Authority: WO
Inventors: Dino Duso
Original assignee: Rovera G.M. S.P.A.
Priority date: 2009-11-27
Filing date: 2009-11-27
Publication date: 2011-06-03

Abstract

A moving portal (1) for a measuring machine or a machine tool is described, comprising at least one pair of uprights (3a, 3b) supporting on their upper part at least one ledger (5) equipped with at least one measuring feeler arm or vertical tool-holder arm (7), each upright (3a, 3b) comprising on its lower part at least one respective base (11a, lib) equipped with supports sliding along a pair of guiding rails (15a, 15b), further comprising a system for compensating alignment errors of the guiding rails (15a, 15b), comprising at least one sliding support (16) arranged between at least the upright (3a) and the respective base (lla), such sliding support (16) having at least one degree of freedom with direction parallel to an axis (Y) perpendicular to a sliding direction of the portal (1) along the guiding rails (15a, 15b). In addition, the portal (1) comprises a system for balancing itself when working, having two balancing cylinders (2OA, 20B) for its structural stiffening, placed on the external side of the base (Ha).

Description

MOVING PORTAL FOR A MACHINE TOOL OR A MEASURING MACHINE

The present invention refers to a moving portal for a measuring machine or a machine tool, in particular for a vertical milling machine of the "Gantry" type with fixed or moving ledger, equipped with a system for compensating alignment errors for guiding rails of the portal itself, and thermal expansion errors of the ledger along its main axis.

As known, in the current art, design and manufacturing of machines are more and more requested, such as for example CNC machine tools, Cartesian Robots, or CM measuring machines, for working and automatically measuring objects, even of a complex type and with big sizes, however capable of guaranteeing extremely high working and measuring accuracy.

Massive and precision mechanics have therefore always been the preprequisite for satisfying the request for accuracy, at the expense of cost and dynamic efficiency of the machine itself.

In particular, manufacturing accurate Cartesian axes machines is based on the capability of producing and installing guiding structures and rails that must be perfectly straight and perpendicular one to the other.

This, consequently, needs an extremely precise and accurate work for laying the rails, usually with the help of laser guides adapted to point out the straightness of individual rails and installation positions able to guarantee their mutual parallelism, that necessarily affect installation times and costs for the whole machine .

Moreover, though at the end of laying, the rails are perfectly straight and mutually parallel, there are numerous interferences, above all coming from the external environment, that can impair such situation: in particular, since the rails, usually made of steel, are typically secured onto concrete basements, the different thermal expansions of the two materials due to possible temperature changes, generate a subsequent rail distortion, determining a lack of parallelism, that mechanically and dynamically affect the whole machine tool.

Therefore, as an alternative to the absolute accuracy of the mechanics, and in particular of the guiding rails positioning, the art has been developed for building alternative systems based on elctronics and servo-mechanisms, whose purpose is electronically cancelling the error produced by mechanical distortions to provide new placement heights to the control, that correct the machine and take it back into its correct position.

Object of the present invention is solving the above prior art problems by providing a moving portal for a measuring machine or a machine tool, in particular for a vertical milling machine of the "Gantry" type with fixed or moving ledger, equipped with a system for compensating alignment errors of the guiding rails of the portal.

Another object of the present invention is providing a moving portal for a measuring machine or a machine tool that, due to a system for compensating the alignment errors of the guiding rails, can move along the rails even when there is not a perfect parallelism between them without generating mechanical distortions on the portal.

Moreover, an object of the present invention is providing a moving portal for a measuring machine or a machinet tool that, due to a system for compensating the alignment errors of the guiding rails, allows a quicker and less costly laying of the rails.

The inventive system de facto adds one degree of freedom to the portal, and more precisely allows translating the uprights on the left side.

The present invention also provides for a balancing system through two lateral cylinders, devised for obtaining a double result: on one hand, the portal is allowed to slide on the basement for the above-mentioned reasons, and on the other hand, the movement due to working forces and ram-carrier base dynamics is compensated for.

The above and other objects and advantages of the invention, as will appear from the following description, are obtained with a moving portal for a measuring machine or a machine tool equipped with a system for compensating the alignment errors of the guiding rails of the portal as claimed in claim 1.

Preferred embodiments and non-trivial variations of the present invention are the subject matter of the dependent claims.

It will be immediately obvious that numerous variations and modifications (for example related to shape, sizes, arrangements and parts with equivalent functionality) can be made to the invention without departing from the scope of the invention as appears from the enclosed claims.

The present invention will be better described by some preferred embodiments thereof, provided as a non- limiting example, with reference to the enclosed drawings, in which: FIG. 1 shows a front view of a preferred embodiment of the moving portal 1 according to the present invention;

FIG. 2 shows an enlarged view of the part in box A in FIG. 1;

FIG. 3 shows a side view of the part in FIG. 2;

FIG. 4 shows an enlarged view of the part in box B in FIG. 3;

FIG. 5 shows a side view of another preferred embodiment of the moving portal 1 according to the present invention;

FIG. 6 shows an enlarged view of the part of box C in FIG. 5; and

FIG. 7 shows a sectional view of the part in FIG. 6.

With reference to the Figures, it is possible to note that the moving portal 1 according to the present invention for a measuring machine or a machine tool, such as preferably a milling machine of the "Gantry" type, comprises at least one pair of uprights 3a, 3b supporting on their tops at least one ledger 5 with which a measuring feeler arm or vertical tool-holder arm 7 operatively cooperates, on the lower head 9 of which, through known fastening systems, realised for example as at least one spindle, tools can be secured with vertical rotation axis, such as for example a milling head, each upright 3a, 3b further comprising on its lower part at least one respective base 11a, lib equipped with sliding supports, commonly made as sliders 13 with pre-loaded rollers that allow the portal 1 to move along a pair of guiding rails 15a, 15b.

Advantageously, the portal 1 according to the present invention further comprises a system for compensating the alignment errors of the guiding rails 15a, 15b of the portal 1 itself: by fixing a Cartesian triad of orthogonal reference axes XYZ oriented according to known conventions adopted for machine tools, it is possible to note that the system for compensating the alignment errors of the portal 1 according to the present invention comprises at least one sliding support 16 arranged between at least one upright 3a and the respective base 11a, such sliding support 16 having at least one degree of freedom with a direction parallel to axis Y and perpendicular to axis X, and therefore perpendicular to the sliding direction of the portal 1 along the guiding rails 15a, 15b, and in particular perpendicular at least to the guiding rail 15b.

In such a way, at least the upright 3a is not constrained to its own base 11a and can slide, at least along a perpendicular direction to the sliding direction of the portal 1 along the guiding rails 15a, 15b, related to its own base 11a.

In addition, two lateral balancing cylinders have been assembled onto this system, as shown in figure 3 with parts 20A and 20B; such balancing cylinders correct thw above embodiment, that otherwise results scarcely rigid when working.

The operating principle of this arrangement is as follows: the stem has two identical thrusting surfaces, mutually connected and equipped with a valve that can be calibrated at a certain pressure.

After having defined the calibration pressure, the stem remains fixed and connects the uprights equipped with the sliding guide with fixed base.

Thereby, a value is obtained that can be estimated with the working effort under which the compensating system does not intervene, while in the movement along axis X, when alignment problems for the two basements occur, the relevant force is much greater and therefore de facto the left uprights are freed.

According to at least one preferred embodiment of the portal 1 according to the present invention, as shown in FIG. 1 and 4, the sliding support 16 can be made as at least one sliding slider 16a or preferably, obviously depending on structural dimensions, weight and inertia of the portal 1, as at least one pair of sliding sliders 16a, preferably of the pre-loaded type, sliding along at least one rail 16b parallel to axis Y.

Obviously, any other technical embodiment of the sliding support 16 that allows obtaining at least one degree of freedom with a direction parallel to axis Y and perpendicular to axis X, and therefore allows not constraining at least the upright 3a with respect to the respective base 11a along a direction that is perpendicular to the guiding rails 15a, 15b, and in particular' to the guiding rail 15b, falls within the scope of the present invention.

For such purpose, according to some other possible, alternative and non-limiting embodiments (not shown in the Figures) of the compensating system of the portal 1 according to the present invention, that do not comprise the sliding sliders 16a and the related rails 16b or other mechanic kinematisms or constraints, the sliding support 16 can in fact be realised, for example, as a suspension of the hydrostatic type, with air cushion or with magnetic levitation.

In particular, as shown in FIG. 5 to 7, the sliding support 16 can comprise, in another preferred embodiment thereof, a plurality of rollers interposed and sliding between the upright 3a and its related base 11a along the direction defined by axis Y. In view of what has been described above, the advantages deriving from the moving portal 1 according to the present invention and its related system for compensating the alignment errors of the guiding rails are clear.

In fact, if there is no parallelism between the guiding rails 15a, 15a, the portal 1 can therefore go on sliding along the rails without being subjected to mechanical distortions that would impair the placement of the ledger 5 and the working accuracy of the vertical tool-holder arm 7: in fact, since at least the base 11a is not constrained, at least along the axis Y perpendicular at least to the respective rail 15a, with respect to its own upright 3a, the base 11a can slide along the rail 15a "copying" its behaviour without affecting the placement of the upright 3a with respect to axis Y, thereby avoiding to transmit mechanical distortions to the rest of the portal 1 caused by the absence of parallelism between the rails.

When working, instead, the portal is as rigid as an arrangement with permanently blocked uprights.

Still more, a further advantage that such invention provides to the system deals with the thermal expansion aspect; in practice, when the temperature changes, a structure having the sizes of the ledger is subjected to not neglectable expansions.

Having a system which is free of sliding along the ledger axis allows avoiding that the structure elongation generates distortions of a non-linear nature, as would happen with completely blocked uprights.

The portal 1 according to the present invention therefore, in addition to guaranteeing in time the maximum working accuracy of the machine with which it is equipped also in case there is no parallelism between the rails, allows obtaining a much quicker and inexpensive laying of the rails: in fact, since it is not necessary any more to have an extreme parallelism between the rails to guarantee the maximum accuracy to the machine tool, due to the use of a portal 1 according to the present invention, it is enough to place, in a perfectly straight way, for example by using a laser guide, at least the guiding rail 15b related to the upright 3b without the sliding support 16, while the other rail 15a can be laid, relatively more or less in parallel with the rail 15b and more or less straight, in a quicker and less accurate way without affecting the working and placement accuracy of the portal 1 according to the present invention.

Claims

1. Moving portal (1) for a machine tool or a measuring machine, comprising at least one pair of uprights (3a, 3b) supporting on an upper part thereof at least one ledger (5) equipped with at least one measuring feeler arm or vertical tool-holder arm (7), each upright (3a, 3b) comprising on a lower part thereof at least one respective base (11a, lib) equipped with supports sliding along a pair of guiding rails (15a, 15b), characterised in that it comprises a system for compensating alignment errors of said guiding rails (15a, 15b) and a system for balancing the portal (1) when working, said system for compensating errors comprising at least one sliding support (16) arranged between at least said upright (3a) and said respective base (11a), said sliding support (16) having at least one degree of freedom with a direction parallel to an axis (Y) that is perpendicular to a sliding direction of said portal (1) along said guiding rails (15a, 15b) and two balancing cylinders (20A, 20B) assembled on the sides of the base (11a) .

2. Moving portal (1) according to claim 1, characterised in that said sliding support (16) comprises at least one sliding slider (16a) sliding along at least one rail (16b) parallel to said axis (Y) .

3. Moving portal (1) according to claim 1, characterised in that said sliding support (16) comprises a suspension of an hydrostatic type.

4. Moving portal (1) according to claim 1, characterised in that said sliding support (16) comprises a suspension of a pneumatic type.

5. Moving portal (1) according to claim 1, characterised in that said sliding support (16) comprises a suspension with magnetic levitation.

6. Moving portal (1) according to claim 1, characterised in that said sliding support (16) comprises a plurality of rollers.

7. Moving portal (1) according to claim 1, characterised in that said machine tool is a milling machine of a "Gantry" type.