EP1097781A2

EP1097781A2 - Apparatus for finishing metal surfaces

Info

Publication number: EP1097781A2
Application number: EP00124142A
Authority: EP
Inventors: Paolo Franco Zanella
Original assignee: ANTIL Srl
Current assignee: ANTIL Srl
Priority date: 1999-11-08
Filing date: 2000-11-07
Publication date: 2001-05-09
Also published as: ITMI992330A0; ITMI992330A1; EP1097781A3; IT1314012B1

Abstract

Apparatus for surface finishing of metal pieces, in particular for satin-polishing extractor hoods (10) and the like. The apparatus comprises a first work unit (17) provided with a rotating brush (18) and a second work unit (14) for supporting the metal piece (10), which can be positioned frontally one in relation to the other. Both work units (14, 17) are movable along respective slide guides (12, 13; 15, 16) in planes at right angles one to the other; each work unit (14, 17) is also provided with three controlled axes (Al, A2, A3; A4, A5, A6), each of which is operatively connected to a control device designed to send reference signals to a programmable process unit (CPU) so as to sequentially orientate each surface (S) of the metal piece (10) along a reference plane, for example parallel to the vertical sliding plane of the work unit (17) for supporting the rotating brush (18), and respectively to move the same brush (18) along two orthogonal axes (A2, A5) parallel to the reference plane, according to a programmed work path (D0-D9).

Description

FIELD OF THE INVENTION

The present invention relates to a surface finishing apparatus for finishing the surfaces of metal pieces, in particular large-sized parts which have flat or arch-shaped surfaces diversely arranged and orientated one in relation to the other.
Although the invention is described hereinbelow with reference to the operations of satin-polishing extractor hoods in stainless steel, the invention can however advantageously be applied for the finishing of any metal surface, where "finishing" refers to any operation of cleaning, polishing, satin-polishing, grinding or similar operations, performed by means of rotating brush which are moved and maintained in contact with the surface to be finished.
As is known, the operations of surface finishing of metal pieces in general are performed by means of appropriate automatic apparatus which grip, clean and/or polish and unload the polished pieces. Apparatus of this kind are described in EP-A-0 458 758 and EP-A-0 487 460. These apparatus in general are intended for cleaning and for polishing pieces which are small in size or have complex shapes, for example taps, handles, cutlery, pans and the like. Due to their complexity these apparatus adapt with difficulty to the finishing of large-sized pieces, in particular the satin-polishing of extractor hoods in stainless steel and the like.
Currently the finishing or satin-polishing operations of metal extractor hoods or similar pieces, defined by large surfaces diversely arranged and orientated, are performed by means of extremely complex and bulky devices, which provide for the use of several fixed tools while the part to be worked is kept in motion so as to position it and orientate the same in relation to each working tool, or by maintaining the working tools in motion in relation to the fixed part to be polished. Each tool or the part to be polished is supported by respective multiaxis and robotised work units, capable of performing various angular movements so as to maintain working contact constantly between brush and part to be polished, following the shape and/or the profile of the latter.
Apparatus of this type, due to their actual functional complexity and structure, in general use numerical control (CNC) programming systems, somewhat difficult to manage in that they require extremely long programming times, of the order of some days, with consequent stoppage of production. Moreover programming of these apparatus has to be carried out by specialist staff.
Apparatus of this kind, due to their poor working flexibility, were found to be suitable and are mainly used for mass production, being wholly unsuitable for operating a limited number of pieces or in the case wherein frequent changing of the work program is required.
Apparatus of a known type, due to the functional and structural complexity, are also high in cost and difficult to manage.

OBJECTS OF THE INVENTION

The main object of the present invention is to provide apparatus for surface finishing of metal pieces, which is structurally simple and easy to program.
In particular the invention relates to an apparatus for satin-polishing extractor hoods in steel, which is of a new design and capable of operating automatically on flat and large-sized surfaces or which extend in at least one longitudinal direction.
A further object of the present invention is to provide apparatus as defined above, which uses two simple robotised work units each having a limited number of work axes controlled and managed by an easily programmable process unit, which allows extremely short programming times, within the reach of any operator, whereby it is possible to operate selectively on each surface of the extractor hood, acting in sequence over consecutive bands along a programmed work path.
Yet another object of the invention is to provide apparatus of the kind defined above, wherein each of two work units performs simple movements of linear translation and/or rotation in relation to a system of Cartesian axes, in this way allowing extreme simplification of the structure and overall dimensions of the same apparatus, and a drastic reduction in costs compared to previously used apparatus.

BRIEF DESCRIPTION OF THE INVENTION

The above can be achieved by means of apparatus for finishing surfaces of metal pieces according to claim 1.
More specifically, according to the invention, apparatus has been provided for finishing surfaces of metal work-pieces, comprising a support frame for a first and a second work unit which can be positioned frontally one in relation to the other in a manner controlled by a process unit, characterised in that it comprises:

a first work unit for supporting a metal work-piece, said first work unit being movable along a first sliding plane, and being made and set up with several work axes to orientate selectively at least one surface of the metal work-piece, parallel to a predetermined reference plane;
a second work unit provided with a rotary brush, said second work unit being movable along a second sliding plane at right angle to a sliding direction of the support unit for the metal work-piece, said second work unit being made and set up with several work axes so as to orientate and to move the rotating brush in relation to the metal work-piece parallel to said reference plane, maintaining a constant contact pressure; and
in that a process unit is provided comprising programmable control means associated with each work axis to selectively orientate the surfaces of the work-piece in relation to said reference plane, and respectively to move sequentially the rotating brush over each surface of the work-piece, along a programmed work path.

BRIEF DESCRIPTION OF THE DRAWINGS

The apparatus for finishing metal surfaces, according to a preferred embodiment of the invention, and the mode of operation of the same, will be described in greater detail hereinbelow with reference to the accompanying drawings, in which:
Fig. 1 is a perspective view of an extractor hood to be satin-polished;
Fig. 2 is a top view of the apparatus according to the invention;
Fig. 3 is a front view of the apparatus of Fig. 2;
Fig. 4 is a side view of the apparatus of Fig. 2;
Fig. 5 is an enlarged detail of the support unit for the extractor hood;
Fig. 6 is a view similar to that of Figure 5 with sectioned parts;
Fig. 7 is a cross-sectional view along line 7-7 of Figure 5;
Fig. 8 is an enlarged detail of the arm for supporting the rotary brush;
Fig. 9 is a block diagram of the programming and drive system.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 represents schematically a metal piece to be worked, in the form of an extractor hood 10 in stainless steel, which has to be finely satin-polished on its external surfaces.
The mechanical operation of satin-polishing of the external surfaces of the extractor hood takes place, in a manner in itself known, by means of a rotary brush, moving it in contact with the surface to be satin-polished, along a programmed work path, represented for example by the dotted line L on the surface S1 in Figure 1, and maintaining a work pitch P along each band, substantially equal to the thickness of the brush. The operation of satin-polishing or more generally of finishing in the case of the surface S1 takes place by operating sequentially along the various bands wherein the surface S1 can be considered ideally divided.
With traditional techniques which use anthropomorphic robots having 6 degrees of freedom for supporting the extractor hood and for movement of the brush, during programming it is necessary to plot the path by points D0-D9, supplying the control unit with a very high number of data. According to the present invention, wherein two work units are used, movable along the axes of a Cartesian reference system, each of which is also provided with only three powered axes for orientation of the extractor hood and for positioning the rotary brush respectively, and wherein, thanks to a particular orientation of the surface, which at a given moment has to be worked, in relation to a reference plane substantially parallel to the plane of movement of the same work brush, it is however possible to simplify considerably the entire apparatus and consequently program the electronic control unit by means of a much smaller number of data, making the same apparatus wholly accessible to any user and programmable in an extremely short period of time.
A preferred embodiment of apparatus for surface finishing of metal pieces according to the invention is shown, by way of an example, in Figures 2 to 8 of the accompanying drawings.
In particular, with reference to Figures 2, 3 and 4, the apparatus comprises a three-dimensional frame 11 substantially consisting of a series of uprights and crosspieces rigidly connected one to the other.
Two of the lower crosspieces 12 and 13 in Figure 2 comprise longitudinal guides 12A, 13A which extend in a horizontal sliding plane along an axis A1 for a first work unit 14 for supporting the extractor hood 10.
Similarly two of the uprights 15 and 16 of the frame 11 (Figure 3), are provided with vertical guides 15A, 16A along a sliding axis A2 for a second work unit 17 for supporting a rotary brush 18 movable in a vertical plane, at right angles to the sliding axis A1 of the first work unit 14.
The two sliding planes for the work units 14 and 17 form part of a system of reference Cartesian axes for programming a process and control unit, with the process data of each surface of the extractor hood 10 to be satin-polished.
In particular, as shown in the various figures, the unit 14 for supporting the extractor hood 10, comprises a first carriage 19 sliding along the guides 12A and 13A, so as to move the extractor hood 10 respectively close to and away from the work brush 18 carried by the second work unit 17.
The carriage 19 is moved along the slide guides 12A, 13A for example by means of a belt transmission system comprising belts 20 at the crosspieces 12 and 13, connected one to the other by a synchronism axis 21 which receives the movement from a geared motor 22 connected to a signal generator 23, such as a resolver or another device suitable for supplying to the process unit a reference signal of the position of the carriage 19 along the axis A defined by the slide guides 12A, 13A.
The work unit 14 also comprises a body 24 which extends upwards from the carriage 19, ending above with an overturnable part 25 for supporting the extractor hood, capable of rotating angularly along a horizontal axis 26 defining a third controlled axis A3, parallel to the sliding planes of both work units 14 and 17.
More specifically, as shown in the enlarged details of Figures 5 and 7, the overturnable support 25 comprises a large pulley 27 fastened to the same support 25, which pulley 27 is connected, by means of a belt 28, to a second pulley 29 carried by a pivotable arm 30. The pulley 29 is in turn connected to the shaft of a geared motor 31 connected to a resolver 32 or signal generator suitable for supplying a reference signal of the angular position or slant assumed by the same support 25.
Again with reference to the sections of Figures 6 and 7, the pivotable support 25 extends upwards with a sleeve 33 rotatingly supported by a pin 33' which allows rotation of the extractor hood 10 through 360°, along a fourth controlled axis A4 (Fig. 2), so as to position selectively each of the lateral surfaces of the extractor hood 10 in front of the rotating brush 18.
The sleeve 33 is provided with gripping members 34 for gripping the extractor hood 10 and can be made to rotate by means of a belt 35 and a geared motor 36 provided with a resolver 32 or signal generator 37 designed to supply signals indicative of the angular position assumed by the extractor hood 10 in relation to a zero position of the controlled axis A4 defined by the pin 33'.
On the basis of what has been previously referred, the unit 14 for supporting the extractor hood 10 or more generally of the metal piece to be worked, is therefore provided with three controlled axes, including a first axis A1 for longitudinal sliding of the carriage 19, along a horizontal plane defined by the lateral guides 12A and 13A, as well as two controlled rotational axes A3, A4 at right angles one to the other for a first overturning movement of the extractor hood 10 towards the brush 18, and respectively for a second rotational movement designed to orientate selectively the lateral surfaces of the extractor hood 10 in relation to a predetermined reference plane.
Purely by way of an example, reference plane can refer to a vertical plane parallel to the vertical axis A2, for example a plane passing through the rotational axis 26 of the upper part 25 of the support unit for the extractor hood, parallel to the sliding plane of the support unit 17 of the brush.
The second work unit 17 is shown in Figures 2, 3 and 4 of the drawings, while Figure 8 shows an enlarged detail of the pivotable arm for supporting the work brush 18 and the drive system.
As shown in the various figures, the second work unit 17 comprises a second carriage 36 which extends crosswise and which moves vertically along the guides 15A, 16A of the two rear uprights 15 and 16, parallel to the ideal reference plane mentioned previously, for the selective positioning of the lateral surfaces of the extractor hood to be satin-polished.
The carriage 36 is moved by means of a belt system 37 (Figure 3) connected by means of a synchronism axis 37' which receives the movement from a geared motor 38 provided with a reference signal generator 38', such as a resolver, in a similar manner to what was referred previously for the first carriage 19 designed to supply reference signals of the position of the same carriage 36, along a controlled reference axis A2 at right angles to the previous controlled axis A1.
The carriage 36 is in turn provided with a pair of longitudinal guides 36A for a slide 39, in turn driven by a belt system 40 which receive the movement from a geared motor 41. The geared motor 41 is in turn provided with a signal generator 42 for supplying information on the position of the slide 39 on the slide guides 36A, in the direction of the controlled axis A5 defined by the same guides (Figure 3).
From the slide 39 a horizontal arm 43 projects, whose front part 44 is capable of rotating along a controlled rotational axis A6, at right angles to the sliding plane of the same slide, so as to position the work brush 19 in a vertical plane, as shown, or in a horizontal plane, or in any other plane as required. The rotation of the front part 44 of the arm 43 for the brush 18 can be obtained, similarly to the support 25 for the extractor hood 10, by means of a respective geared motor, not shown, and a corresponding signal generator suitable for supplying an indication of the positioning plane of the same brush 18.
The rotating brush 18, as shown in greater detail in Figures 2, 4 and in Figure 8, is in turn supported by a pivotable arm 45 hinged in 46 to the rotating front part 44 of the horizontal support arm 43.
The brush 18 receives the movement from a geared motor 47 whereto it is connected by means of a pulley system and transmission belts 48 and 49.
The arm 45 for support of the brush 18 can be angularly moved by a slanted stop surface 50 and, in relation to a "zero" or work position, by means of a pneumatic drive cylinder 51, as shown. Also connected to the rod of the drive cylinder 51 is a position transducer 52, provided for example by a linear potentiometer, capable of giving an indication relating to the angular position assumed by the arm 45 for the brush 18, in relation to the aforementioned "zero" position. In this way, by acting on the drive cylinder 51, it is possible to orientate the brush 18 into a correct working position, and maintain the same brush constantly in the required position, in contact with the work surface of the extractor hood 10, exerting a constant work pressure; in this way automatical compensation of the wear degree of the brush is obtained.
The second work unit 17 also comprises three controlled axes two of which are at right angles one to the other for a sliding movement and a third one for rotation, in addition to orientation axis of the arm 45 for supporting the rotating brush 18.
Figure 9 of the accompanying drawings shows a block diagram of the electronic control equipment for the two work units 14 and 17 described previously.
As can be seen from Figure 9, the electronic control equipment comprises a central process unit consisting for example of a CPU, having a first permanent memory unit 60, for example a ROM memory containing the work program which governs operation of the entire apparatus. A second programmable memory unit 61, for example a RAM memory, is provided for storing the variable data, that is to say the management program for each controlled axis A1-A6, as a function of the dimensions and shape of the surfaces of the extractor hood or of the piece to be worked.
The CPU, by means of a BUS 63, is capable of dialogue, i.e. of transmitting and receiving data from the six control units 64-69 which govern the controlled axes A1-A6 of the work unit 14 and respectively of the second work unit 17, as described previously.
Reference 70 in Figure 9 instead denotes the control unit which governs the motor 47 so as to adapt the rotational speed of the brush 18 to its wear state, while 52 denotes the block representing the homonymous position transducer of the rocking arm 45 which supports the rotating brush. The signal of the position transducer 52, by means of the BUS 63, is fed back to the controlled axes of the carriages 19, 36 of the two work units 14, 17 to perform a tracking function when it is necessary to carry out brushing or an oscillating finishing operation of the various surfaces of the extractor hood or of the piece to be worked.
The operation of the apparatus, according to the method of the present invention, will be illustrated briefly hereinbelow with reference to the various figures of the accompanying drawings.
One of the main advantages of the present invention, which results from the use of the two movable work units according to a system of Cartesian axes each having three controlled axes, as previously referred, consists in an extreme simplification of the programming of the entire work apparatus.
In fact, as shown by way of an example in Figure 1, in order to program the work path L of the brush 18, by means of a conventional system it is necessary to proceed by points, plotting all the positions from DO to D9 and programming a very high number of data.
In fact, since each position D0-D9 in a system which uses anthropomorphic robots, is defined by twelve variants, it is clear that in the case above referred to, supposing that the brush is moved without transverse oscillations, 131 items of data have to be monitored for each of the four lateral surfaces of the extractor hood 10, to which the data relating to the other surfaces located along the lower edge and above the extractor hood itself have to be added.
In the case wherein an oscillating movement is to be added for the brush 18, the number of items of data to be monitored and to be set would increase considerably further.
Contrarily, according to the present invention, in the case wherein satin-polishing for example of the surface S1 has to be programmed, it is possible to monitor and set a considerably lower number of data compared to the known systems.
In particular, in the case of the surface S1 in Figure 1, it is sufficient to pick-up the data relating to the starting position P0 and set the space A between the point P0 and the point P1 in the direction of the horizontal axis of the reference plane, the space B between the point P1 and the point P3 in the direction of the vertical axis of the reference plane, the space C1 between the point P0 and the point P2 in the direction again of the horizontal axis of the reference plane, and finally the space C2 between the point P2 and the point P3 in the previous direction, for a total of 11 items of program data in addition to the pitch K, compared to the 131 of the example previously referred. In the case wherein oscillating brushing is required, it will be sufficient to add one single variable item of data relating to this function.
According to the present invention, for the satin-polishing of the surfaces of the hood 10 the procedure is the following: initially the extractor hood is in the vertical position shown in Figures 2 to 4 spaced apart from the brush 18 which is totally raised.
It is now supposed that the four lateral surfaces of the extractor hood are to be satin-polished in sequence; in this case, by acting on the first work unit 14, the extractor hood 10 is tilted, positioning the first surface S1 vertically or parallel to the previously mentioned reference plane.
Then the brush 18 is orientated, with its rotation axis in a vertical position, at the starting point P0, picking-up the data relating to the coordinates of this point. The brush is then moved into the other reference points P1, P2, P3 in order to pick-up the respective positions or spaces A, B, C1 and C2, from which the programming data are to be obtained.
In the case wherein the extractor hood has different dimensions on the other two sides at right angles to the previous ones, the extractor hood 10 will be rotated through 90°, once again picking-up the various reference items of data in the manner described and memorising the various sequences for selective positioning of the various surfaces of the extractor hood to be worked.
Once the program data for all the surfaces of the extractor hood 10 have been picked-up, the apparatus will be able to carry out automatically, and in sequence, all the work phases, moving the brush 18 and/or the same extractor hood 10 in order to position in sequence the various surfaces parallel to the reference plane, always maintaining a constant work pressure of the brush 18 whose position will be constantly monitored and controlled automatically so as to compensate wear.
In this way a satin-polishing operation is performed, or more generally an operation of surface finishing of metal pieces to be worked by means of an apparatus easy to program in an extremely short length of time and within the reach of any user, versatile and capable of adapting to many working needs, and which at the same time has comparatively small overall dimensions and cost.
In any case, what has been shown and described with reference to the satin-polishing operation of an extractor hood in stainless steel can equally be adopted for other finishing operations of metal pieces, whose lateral surfaces can on each occasion be orientated appropriately, through simple rotation and/or overturning, parallel to a reference plane in relation whereto the brush or work tool performs solely linear movements along two orthogonal axes, parallel to the same surface of the piece to be worked.
What has been said and shown with reference to the accompanying drawings has been given purely by way of example of a preferred embodiment. Therefore other modifications or variants may be made as regards the guiding and driving systems the work units, or as regards the driving means of the controlled axes and the means for picking up the various parameters or reference data, without thereby departing from the attached claims.

Claims

Apparatus for the surface finishing of metal pieces (10), comprising a support frame (11) for a first and a second work unit (14, 17) which can be positioned frontally one to the other in a controlled manner by a process unit (CPU), characterised by comprising:

a first work unit (14) for supporting a metal work piece (10) to be worked, said first work unit (14) being movable along a first sliding plane (13), and being made and set up with several work axes (A1, A3, A4) to selectively orientate at least one surface (S) of the metal piece (10), parallel to a predetermined reference plane;

a second work unit (17) provided with a rotating brush (18), said second work unit (17) being movable along a second sliding plane (15, 16) at right angles to the sliding direction of the support unit (14) for the metal piece (10), said second work unit (17) being made and set up with several work axes (A2, A5, A6) to orientate and move the rotating brush (18) in relation to the metal piece (10), parallel to said reference plane, while maintaining a constant contact pressure;

and in that a process unit (CPU) is provided with programmable control means (64-70), associated with each work axis (A1-A6) of the work units (14, 17) to selectively orientate the surfaces (S) of the piece (10) to be worked in relation to the aforementioned reference plane and respectively to sequentially move the brush (18) along each surface (S) according to a programmed work path (D0-D9).
Apparatus according to claim 1, characterised in that the first work unit (14) comprises drive means (19) for moving the same work unit (14) along a first sliding axis (13 - A1) at right angles to the aforementioned reference plane, and for selectively orientating the surfaces of the metal piece (10) according to a first and a second rotational axis (26, 33 - A3, A4) at right angles one to the other.
Apparatus according to claim 2, characterised in that said axes comprise a first rotational axis (26 - A3) parallel to the sliding planes for the support unit (14) of the metal piece (10) and respectively of the support unit of the brush (18).
Apparatus according to claim 2 or 3, characterised in that said sliding and rotational axes (A3, A4) are controlled by the process unit (CPU).
Apparatus according to claim 1, characterised in that the second work unit (17) comprises drive means (38, 41, 51) for moving the same work unit (17) along two sliding axes (A2, A5) at right angles one to the other, and parallel to the aforementioned reference plane, respectively for orientating the brush along a rotational axis (46 - A6) at right angles to the plane of the two sliding axes (A2, A5).
Apparatus according to claim 5, characterised in that said sliding and rotational axes (A2, A5, A6) are controlled by the process unit (CPU).
Apparatus according to claim 1, characterised in that the rotating brush (18) is supported by a pivotable arm (45), and in that it comprises means (51, 52) for driving and monitoring the angular position of the brush support arm (45), controlled by the process unit (CPU).
Apparatus according to claims 6 and 7, characterised in that the pivotable arm (45) is hinged to a rotating arm (44) having a controlled axis of rotation, at right angles to the sliding axes (A2) of the same support unit (17).
Apparatus according to claim 8, characterised in that said rotating arm (44) comprises means (50) for stopping and angular positioning of the pivotable arm (45).
Apparatus according to claim 1, characterised in that the first work unit (14) comprises a carriage (19) sliding along guides (12, 13) laying in a horizontal plane, and a support member (34) for the metal piece (10), said support member (34) being arranged on said carriage (19) for rotational movements along two orthogonal axes (A3, A4).
Apparatus according to claim 1, characterised in that the second work unit (17) comprises a slide (39) for supporting the brush (18), said slide (39) being movable along horizontal guides (36A) of a second carriage (36) mobile along vertical guides (15, 16), parallel to the aforementioned reference plane.
Apparatus according to claim 1, characterised in that said process unit comprises a programmable control unit (CPU), operatively connected to drive means (19, 31, 36; 38, 41, 51) for sliding and rotation axes of said first and second work units (14, 17).