WO2002006762A1

WO2002006762A1 - Apparatus for the dimensional and/or geometrical checking of mechanical pieces with rotational symmetry

Info

Publication number: WO2002006762A1
Application number: PCT/EP2001/007794
Authority: WO
Inventors: Valerio Lazzari
Original assignee: Marposs SpA
Current assignee: Marposs SpA
Priority date: 2000-07-14
Filing date: 2001-07-06
Publication date: 2002-01-24
Anticipated expiration: 2003-01-14
Also published as: ITBO20000427A1; ITBO20000427A0

Abstract

An apparatus for the dimensional and/or geometrical checking of mechanical pieces (11) with rotational symmetry comprises a support structure (1, 3) with support and reference elements (13, 16, 25, 31, 33), for supporting and positioning the piece, that define a longitudinal reference axis, and gauging heads (73, 77). In order to check the piece while it is rotating, there is provided a transmission system including an axially rotary support (45) whereto there are coupled, by means of hinges (44), two arms (41) carrying jaws (43) for clamping the piece. A pulley (49), fixed to the support structure and driven into rotation by a motor (53), transmits the axial rotation to the support carrying the arms by means of a coupling including an Oldham joint (47).

Description

DESCRIPTION

«APPARATUS FOR THE DIMENSIONAL AND/OR GEOMETRICAL CHECKING OF MECHANICAL PIECES WITH ROTATIONAL SYMMETRY»

Technical Field

The present invention relates to an apparatus for the dimensional and/or geometrical checking of a mechanical piece, that defines at least a surface of rotation and an axis of symmetry of said surface, including a support structure with support and reference elements for supporting and positioning the piece to be checked, that define a longitudinal reference axis and reference surfaces for positioning the piece to be checked in such a way that the axis of symmetry and the longitudinal reference axis substantially coincide, driving devices coupled to the support structure, a transmission system, with a rotary support rotating about a longitudinal axis of rotation, coupled to the driving devices and adapted for cooperating with the piece for transmitting rotational displacements of the piece about the axis of symmetry, and checking devices, coupled to the support structure and adapted to cooperate with the piece to be checked.

Background Art

There are known apparatuses for the geometrical and/or dimensional checking of mechanical pieces with rotational symmetry, as, for example, brake disks, flanges, drums, etc.. The checkings of these pieces can be carried out while the latter rotate about their axis of symmetry. If these pieces have eccentric holes, the rotation can be implemented by a device including a radial transmission arm that rotates, driven by a motor, about the axis of the piece and carries a hooking element housed in a hole of the piece to be checked. Apparatuses with a similar device are described and illustrated in Italian patent application No. BO99A000675, filed by the company applying for the present patent application.

Another possible technique for making the piece rotate, that does not take into account the reference holes on the pieces, foresees that the support and positioning elements for resting and centering the piece be put into rotation. In the apparatuses that implement this second technique, wherein the support and positioning elements rotate together with the piece in the course of the checking, it is impossible to carry out checkings taking said support and positioning elements as a reference, for example flatness checkings of the piece surfaces perpendicular to the axis of rotation with respect to a reference plane defined by the support elements.

Disclosure of the Invention

Object of the present invention is to achieve an apparatus for the dimensional and/or geometrical checking of pieces with rotational symmetry that guarantees high standards of precision and reliability and can be utilized for the checking of pieces that have different features and nominal dimensions . This and other objects are achieved by an apparatus according to claim 1.

Brief Description of the Drawings

An apparatus according to the invention can be manufactured in conformity with the preferred embodiment hereinafter described with reference to the enclosed sheets of drawings, given by way of non-limiting example only, wherein: Figure 1 is an axonometric view of an apparatus according to the invention;

Figure 2 is an enlarged scale view of a portion of the apparatus shown in figure 1; and

Figure 3 is a partly cut-away longitudinal cross- sectional view, furthermore enlarged and with the omission of some elements, of a part of the portion of the apparatus shown in figure 2.

Best Mode for Carrying Out the Invention

The checking apparatus shown in the figures includes a support structure 1 with a stanchion 3 carrying two guides 5 to which there is coupled a slide 6, the slide 6 is movable along guides 5 and supports a base plate 9. The position of slide 6 is controlled by mechanical microswitches 8. Base plate 9 carries support and reference elements for supporting and positioning a piece 11 to be checked, for example a brake disk, that includes at least a surface of rotation 7 and defines an axis of symmetry of these surfaces. These support and reference elements include a support element 13, with rotational symmetry, including three substantially cylindrical portions 15, 17 and 19 with different external diameter dimensions. The support element 13 - coupled to base plate 9 by means of screws, not shown in the figure - has an axial through hole 10 that defines at one end a seat 12. A substantially cylindrical element 16 is inserted in hole 10 and includes a flange housed in seat 12. Element 16, that is coupled to the support element 13 by means of screws (not shown in the figure) , defines a cylindrical seat 21 in which there is housed a substantially tubular element 25 sealed at one end and a compression spring 23, partially arranged inside element 25. The arrangement is provided in such a way that spring 23 applies a force for displacing the sealed end of tubular element 25 away from the bottom of seat 21. Furthermore, the support and reference elements include a plate 31 and a centering nosepiece 33. Plate 31 includes a central hole and a substantially annular relief rim 35 with an annulus-shaped plane surface 37 that has a coating of hard and wear-resistant material, for example ^λΛWidia". Surface 37 defines a reference surface for the piece 11 to be checked. Plate 31 is screwed to the second portion 17 of the support element 13 by means of screws. The centering nosepiece 33, that is coupled to the substantially tubular element 25 by means of screws not shown in the figure, has a substantially frusto-conical surface 34 for centering and positioning piece 11 and rests, by means of the substantially tubular element 25, on spring 23 that enables limited axial translation displacements of nosepiece 33. These axial displacements are limited by surfaces of the support element 13 and of the substantially tubular element 25 and by the head of a screw 32 coupled to the substantially cylindrical element 16. Nosepiece 33 and plate 31 define a longitudinal reference axis for piece 11. In practice, when piece 11 is in the checking position shown in the figures, namely it is resting and centered on the reference surfaces 37 and 34 of plate 31 and nosepiece 33, respectively, the axis of symmetry of piece 11 and the aforementioned longitudinal reference axis coincide.

A system for the automatic displacement of piece 11 includes a mechanic conveyor 39 of the known type for conveying piece 11 towards the interior of the apparatus and clearing it away when the checking operations have been carried out .

A transmission system for communicating to piece 11 a motion of rotation about the axis of symmetry comprises two arms 41, each including a first portion 41' and a second portion 41' ' , both substantially L-shaped, rigidly coupled to each other by means of screws. The first portion 41' of each arm 41 carries at a free end thereof a jaw 43 with a clamping surface with a V-shaped cross-section for contacting the surface of rotation 7 of piece 11. The coupling of each jaw 43 to its associated arm 41 includes screws and pins for enabling it to perform limited rotational displacements, relative to arm 41, about axes substantially parallel to the longitudinal reference axis and perpendicular to it, for facilitating the correct cooperation between the associated clamping surface and the surface 7 of piece 11. According to a variant not shown in the figures, the coupling can also include clearance in the longitudinal direction (at each shoulder screw identified by reference number 42 in figure 3) for compensating possible unwanted longitudinal displacements among the elements forming a coupling joint (an Oldham coupling 47 that is hereinafter described) , and compression springs for maintaining the mutual longitudinal arrangements between arms 41 and jaws 43 when the latter do not touch piece 11. The second portion 41' ' of each arm 41 is coupled to a substantially C-shaped rotary support 45, by means of a fulcrum device including, for example, a hinge 44. The hinges 44 enable each arm 41 to rotate, relative to the rotary support 45, about a transversal axis of rotation. The rotary support 45 is coupled to driving devices that cause rotations about a longitudinal axis, as hereinafter described.

The driving devices include a pulley 49 fixed to a support plate 51 integral with stanchion 3, and a motor 53, controlled by an encoder 52, also fixed to support plate 51, and coupled to pulley 49 by means of belts 55. Mutually movable parts of articulated coupling joint 47, for example, an Oldham coupling of a known type, are clamped, by means of screws, to pulley 49 and rotary support 45, respectively. In practice, motor 53 causes rotations of pulley 49 that are transmitted to rotary support 45 by the Oldham coupling 47.

It should be realized that the Oldham coupling 47 does not substantially constrain the mutual position between pulley 49 and support 45 insofar as translations along directions that are parallel or perpendicular to said longitudinal reference axis are concerned, thus enabling the proper transmission of the rotation even when, for example, the axis of rotation of pulley 49 does not perfectly coincide with the longitudinal reference axis. In other words, the use of coupling joint 47 enables to prevent the generating of unwanted stresses between pulley 49 and rotary support 45, in particular in planes perpendicular to the reference axis. Similar stresses could be transmitted - through arms 41 and jaws 43 - to piece 11 and thereby create problems of statical indeterminateness when defining the associated transversal reference position. Thrust devices include two compression springs 57, each with an end housed in a seat 56 of rotary support 45 and the other end coupled to an adjustment screw 54 screwed in a threaded hole 58 of portion 41'' of arm 41. The springs 57 operate on arms 41 so as to urge the clamping surfaces of jaws 43 against surface 7 of piece 11.

By screwing or unscrewing screws 54, it is possible to adjust the force applied by springs 57 to their associated arms 41. Retraction devices include two pneumatic cylinders 59, coupled to support plate 51, and associated pistons 60, each adapted to cooperate with abutment surfaces of portion 41'' for causing arm 41 to rotate about the transversal axis defined by its associated hinge 44 and jaw 43 to retract from piece 11, during the operations for the loading/unloading of piece 11.

Elements for limiting the rotations of arms 41 include, for each arm 41, a screw 62 screwed in a threaded hole of rotary support 45, with its head housed in a seat of the second portion 41'' of arm 41. The abutment of the head of screw 62 with surfaces of the seat of portion 41' ' limits rotations of arm 41 when approaching piece 11. Furthermore, monitoring means include two pairs of inductive proximity sensors 78 of a known type and two elements 80, each screwed to each arm 41 at portion 41''. These elements 80 include suitably shaped surfaces that, together with the inductive proximity sensors 78, monitor the open or closure condition of arms 41. The pneumatic cylinders 59 and the proximity sensors 78 for the two arms 41 are coupled to support plate 51 so as to be symmetrically arranged at diametrically opposite positions with respect to the longitudinal reference axis. Dimensional checking devices of a known type are coupled to various portions of the support structure in order to perform different types of checkings in connection with different surfaces of piece 11. The figure shows, as an example only, gauging heads 73 fixed to a support 75 coupled, by means of screws, to support plate 51. Each head 73 includes a feeler 76, for contacting the surface to be checked of piece 11, and transducer means, of a known type and not shown in the figures, for emitting signals indicative of the displacements of feeler 76 relative to a zero position, defined in the course of a calibration phase. The processing of these signals enables to determine dimensions and/or geometrical characteristics, for example diameters, distances, flatness, concentricity of different surfaces of piece 11.

Other heads 77 can be coupled, for example, to plate 31 for performing, in a known way, similar checkings, for example checkings relating to the flatness of a surface 71 of the brake disk 11 facing plate 31 and positioned on surface 37. The operation of the apparatus is as follows: upon completion of a calibration phase of the apparatus against a master piece, the mechanical conveyor 39 carries piece 11 to a transversal position that substantially corresponds to the checking position, in other terms a position according to which the axis of symmetry of piece 11 is near the longitudinal reference axis. Slide 6, that is in a lower position with respect to the one shown in figure 1, is raised, for example, by means of a suitable automatic mechanism of a known type not shown in figure 1, until nosepiece 33 is inserted in the central hole of piece 11, the reference surfaces 34 and 37 touch surfaces of piece 11, piece 11 detaches from conveyor 39 and a longitudinal checking position - pre-determined on the basis of the geometrical characteristics of the apparatus - is reached. The reaching and the maintaining of said longitudinal position is controlled by microswitch 8. The surfaces of plate 31 and of nosepiece 33 enable the positioning and the centering of piece 11 so that the axis of symmetry of piece 11 coincides with the longitudinal reference axis. Upon the arrival of piece 11 in the checking position, the angular position of rotary support 45 corresponds to the one shown in the figures, i.e. the arms 41 face cylinders 59 and proximity sensors 78. Furthermore, for enabling the insertion of piece 11, the retraction devices are activated and pistons 60 urge jaws 43 to mutually withdraw to an open configuration. The correct occurring of said open configuration can be controlled by the inductive proximity sensors 78 that are connected to known checking units not shown in the figure. When piece 11 is in the checking position, the retraction devices are deactivated and pistons 60 retract hence allowing the clamping surfaces of jaws 43 to be urged, by springs 23 and by virtue of the rotations of arms 41, against the surface 7 of piece 11. At this point motor 53 is activated and drives into rotation, by means of belt 55, pulley 49 and consequently rotary support 45, arms 41, jaws 43 and piece 11.

In the course of the rotation of piece 11, heads 73 and 77 provide signals that are transmitted to suitable processing units (known and not shown in the figure) for carrying out the required dimensional and/or geometrical checkings.

Once the checking operations end, motor 53 is made to stop at a position according to which the angular position of rotary support 45 is such that arms 41 are aligned with pistons 60 and sensors 78, as shown in the figures. The operation for stopping motor 53 is controlled by encoder 52. The retraction devices are activated and pistons 60 operate on arms 41 thereby displacing jaws 43 away from piece 11. Thereafter, slide 6 is lowered, until piece 11 contacts conveyor 39, detaches from reference surfaces 34 and 37 and is carried by conveyor 39 to the output of the apparatus towards the subsequent machining or checking station.

Unlike the known apparatuses, in which the support and reference elements rotate together with piece 11, in an apparatus according to the invention it is possible to perform accurate checkings with respect to the reference surfaces (34, 37) on which the piece rests. For example, according to what is illustrated in a schematic way in the figure and is mentioned above, it is possible to utilize head 77, coupled to plate 31, for checking the flatness of surface 71 of piece 11. Furthermore, an apparatus according to the invention provides remarkable aspects of flexibility of use. In fact, on the one hand it enables to accomplish in a simple and accurate way dynamical checkings of rotating pieces of different type, more particularly pieces that have or do not have eccentric reference holes, and on the other hand it enables to check pieces 11 with nominal diametral dimensions differing from one another, by substituting just a few component parts (it is often sufficient to substitute portions 41' of arms 41) , or without carrying out any substitution when the differences are small (for example within a range of 10 mm) .

Furthermore, the mutual displacement between piece 11 and the support elements tends to eliminate possible foreign matter, as for example machining swarf, on plate 31 that could affect in a negative way the measurement results.

An apparatus according to the invention can be achieved according to embodiments that differ under some aspects from what is herein illustrated and disclosed, for example it can be utilized for checking pieces of another type, as shafts. In this case the piece can be horizontally arranged between stationary centers and driven into rotation by means of two or three arms coupled to a support and carrying jaws clamped to a surface of rotation of the piece. Alike the herein described apparatus, the support for the arms can be coupled to driving devices including a motor through a coupling joint, for example an Oldham coupling or a coupling of another type with similar features.

Other possible embodiments of an apparatus according to the invention can include that the driving devices and the transmission system (and possibly the checking devices) lower on the piece to be checked by means of a suitable slide, and not vice versa.

As far as the checking devices are concerned, there can be utilized other types of known comparators or measuring devices, with feelers or of the contactless type (for example of the optical type) . Moreover, there can be foreseen devices for the non-dimensional checking, for example for detecting surface features of the piece to be checked.

Claims

CLAIMS :

1. An apparatus for the dimensional and/or geometrical checking of a mechanical piece (11) , that defines at least a surface of rotation (7) and an axis of symmetry of said surface, including:

• a support structure (1,3) with

• support and reference elements (9,13,16,25,31,33) for supporting and positioning the piece (11) to be checked, that define a longitudinal reference axis and reference surfaces (34,37) for positioning the piece

(11) to be checked in such a way that the axis of symmetry and the longitudinal reference axis substantially coincide, • driving devices (49,53,55) coupled to the support structure (1,3),

• a transmission system (41,43,45,47), with a rotary support (45) rotating about a longitudinal axis of rotation, coupled to the driving devices (49) and adapted for cooperating with the piece (11) for transmitting rotational displacements of the piece (11) about the axis of symmetry, and

• checking devices (73,77), coupled to the support structure and adapted to cooperate with the piece to be checked, characterized in that the transmission system includes at least two jaws (43) coupled to the rotary support (45) and clamping surfaces for cooperating with said surface of rotation (7) of the piece (11) to be checked for transmitting said rotational displacements, the rotary support (45) being coupled to said driving devices (49) by means of a coupling joint (47) adapted for not substantially constraining the mutual position between the rotary support (45) and the driving devices (49) insofar as translations along directions that are perpendicular to said longitudinal reference axis are concerned.

2. The apparatus according to claim 1, wherein the transmission system also includes at least two arms (41) carrying at free ends thereof said at least two jaws (43) , each of the arms being coupled to the rotary support (45) by means of a fulcrum device (44) that defines a transversal axis of rotation.

3. The apparatus according to claim 2, wherein the transmission system includes thrust devices (57) adapted for cooperating with said at least two arms (41) for urging the clamping surfaces of said at least two jaws (43) against the surface of rotation (7) of the piece (11) .

4. The apparatus according to claim 3, wherein said thrust devices (57) include compression springs arranged between surfaces of the rotary support (45) and of said at least two arms (41) .

5. The apparatus according to claim 4, wherein said clamping surfaces have a substantially V-shaped cross- section.

6. The apparatus according to one of claims from 2 to 5, including proximity sensors (78) for monitoring the angular position of each of said at least two arms (41) about the transversal axis defined by the associated fulcrum device (44) .

7. The apparatus according to one of the preceding claims, wherein said coupling joint (47) is an Oldham joint .

8. The apparatus according to claim 3 or claim 4, including retraction devices (59,60) that are stationary with respect to the support and reference elements, adapted for cooperating with said at least two arms (41) for causing the mutual withdrawal of said at least two jaws (43) .

9. The apparatus according to claim 8, wherein the retraction devices include cylinders (59) and associated pistons (60) adapted for cooperating with surfaces of said at least two arms (41) .

10. The apparatus according to one of the preceding claims, wherein said driving devices include a motor (53) coupled, by means of belts (55) , to a pulley (49) , fixed to said support structure (1,3) and to said coupling joint (47) .

11. The apparatus according to one of the preceding claims, wherein said support structure (1,3) includes guides (5) , a slide (6) being coupled to said guides (5) for supporting and displacing said support and reference elements in a direction parallel to said longitudinal reference axis.