TECHNICAL FIELD

The present invention falls within the scope of the production of machines for finishing a three-dimensional surface of a workpiece, preferably a blade of a gas turbine or compressor. In particular, the present invention relates to a machine for finishing and/or checking a three- dimensional surface of a workpiece and to an automated system comprising such a machine. PRIOR ART

The finishing operation of a three-dimensional surface, as known, represents the final swarf removing operation to which a workpiece is subjected before its use. In particular, this operation serves to bring the dimensions of the workpiece within the tolerance dimensions both from the dimensional and from the geometric point of view (shape and roughness).

In the precision mechanics sector, surface finishing, polishing and/or belt grinding have obviously a considerable importance. Until the early 2000s, these operations were carried out manually. In order to overcome the technological limits linked to manual processing (i.e. mainly in order to increase productivity, reduce production time-costs), machines and/or working assemblies have been developed in order to guarantee repetition and consistency of the final product quality.

An example of these machines is described in the patent application PCT/IB2007/053767. In particular, this application shows and describes a working assembly, in particular for the finishing of a blade of a turbine or compressor. Such assembly comprises a device for supporting a workpiece which configures one or more degrees of freedom of movement for the workpiece itself. The assembly also comprises a structure for supporting and moving a removal head provided with a tool for removing material from the surface of the workpiece. In particular, the support structure configures a plurality of degrees of freedom of movement for the removal head.

The assembly described in PCT/IB2007/053767 also comprises control means which drive the support structure and the support device so that the removal of the material always takes place in a direction substantially normal to said three-dimensional surface.

While allowing a high quality of the final product to be achieved, the assembly described in application PCT/IB2007/053767 has some limits with reference to operating costs and application possibilities. In particular, the tool change operations are a particularly critical aspect since they require the disassembly of the tool from the head which remains connected to the support structure that supports it. This need translates into particularly long machine downtime which in turn affects the final production costs.

In addition to this, this aspect leads to the impossibility of inserting the working assembly in an automated system. In other words, at present, the finishing of turbine or compressor blades, or other similar products, is an operation carried out separately, i.e. outside the automated line (including numerically controlled machine tools and/or manipulators) through which the workpiece is made.

The Applicant has therefore ascertained the need to have a new technical solution which allows the aforementioned drawbacks to be overcome.

SUMMARY

The main aim of the object of the present invention is to provide a machine for finishing a three-dimensional surface of a workpiece which allows the above-mentioned drawbacks to be overcome.

Within this aim, an object of the present invention is to provide a machine which allows to eliminate, or at least to strongly containing, the times associated with tool change operations, while still guaranteeing a high final quality.

Another object of the present invention is to provide a machine which can be easily inserted into an automated line for the production of a workpiece, in particular for the production of a turbine or compressor blade.

Last but not least, an object of the present invention is to provide a machine which is reliable, easy to manufacture at competitive manufacturing costs.

The Applicant has found that the aim and objects listed above may be achieved by removably connecting the operating head, supporting a finishing tool and/or a control sensor, to a head- holder frame moved on multiple axes. In particular, the Applicant has found that the predetermined objects may be achieved by a machine for finishing and/or controlling a three- dimensional surface of a workpiece, comprising a first device for supporting said workpiece and a second device for moving at least a finishing tool of said three-dimensional surface. Such a second device comprises a support and movement assembly for a head-holder frame, wherein said head-holder frame supports an operating head on which the finishing tool and/or the control sensor are installed. The support and movement assembly configures a plurality of degrees of freedom for the head-holder frame.

According to the invention, the operating head is connected to the head-holder frame by means of a clamping unit which, in an activation mode, blocks the tool-holder head to the head-holder frame in a predetermined position and, in a deactivation mode, allows the removal of said tool-holder head from said predetermined position.

Contrary to known solutions, the tool change operation is not completed by removing only the tool already used, but rather by removing the entire support (operating head) of the tool itself. At the end of an operation, be it finishing or checking, the deactivation of the clamping unit allows you to quickly remove the operating head to replace it with another ready-made one on which the tool or sensor necessary for the subsequent processing or subsequent inspection is mounted.

The main advantage that can be reached is therefore that of allowing the reduction of time, and therefore of the related costs, necessary to complete the tool change operations. Furthermore, the positioning of the operating head in the working position, as well as its removal, may also be carried out by means of a manipulator or in any case an automated system. The machine according to the invention can therefore be inserted in an automated production system.

LIST OF FIGURES

Further features and advantages will appear more clearly from the description of preferred but non-exclusive embodiments of the invention, shown by way of a non-limiting example in the accompanying drawings, in which:

- Figures 1 and 2 are perspective views, each in a possible operating configuration, of an embodiment of a machine for finishing and/or checking a three-dimensional surface of a workpiece according to the present invention;

- Figure 3 is a detailed view of a head-holder frame of the machine of Figures 1 and 2;

- Figure 4 is a perspective view relating to a group of components of the machine of Figures 1 and 2;

- Figure 5 is a perspective view relating to a possible embodiment of some components of the group of Figure 4;

- Figure 6 is a perspective view of another embodiment of a group of components of a machine according to the invention;

- Figure 7 is a perspective view of two components of the group of Figure 6. DETAILED DESCRIPTION

With reference to the aforementioned figures, the machine according to the invention is generally indicated with the reference numeral 1 and is used for finishing and/or checking a three-dimensional surface of a workpiece, preferably for finishing the surface of a blade of a turbine or compressor.

The expression “surface finishing” wants to indicate generically all those mechanically similar operations, such as polishing, lapping or grinding, which are traditionally carried out on a workpiece in order to bring the dimensions and/or shapes of the surfaces of the workpiece itself within predetermined tolerances. Within the scope of the present invention, the term “surface finishing” also includes a possible shot peening operation which consists in making microspheres of variable shape and composition adhere to the surface of the workpiece by means of a violent jet of compressed air coming out of a nozzle. The machine 1 according to the invention comprises a first device 10 which supports the workpiece 5. Preferably, the first device 10 configures a plurality of degrees of freedom for the workpiece 5.

The machine according to the invention also comprises a second device 20 for supporting and moving a finishing tool 15, which may be, for example, an abrasive belt or an abrasive wheel and/or a surface control sensor.

According to the invention, the second device 20 comprises a support and movement assembly 25 which supports and moves a head -holder frame 21 (hereinafter referred to only as “ frame 21”). Said frame 21, in turn, supports an operating head 22 (also indicated with the expression “ head 22”). For the purposes of the invention, the expression “ operating head ” generically indicates a component that supports/carries a finishing tool or a control tool of the surface of the workpiece.

In particular, the second device 20 configures a plurality of degrees of freedom for the frame 21 and therefore for the head 22 when it is connected to the frame 21.

According to the invention, the head 22 is connected to the frame 21 by means of a clamping unit 30 which when activated (activation mode) firmly blocks the head 22 to the frame 21 in a predetermined position (hereinafter also referred to as the working position). In a deactivation mode, the clamping unit 30 does not exert any constraint on the head 22 and allows the removal of the latter from the frame 21. In other words, the clamping unit 30 constitutes a temporary connection interface, i.e. it allows a removable connection, between the head 22 and the frame 21.

Figures 1 and 2 are views respectively relating to a first and to a second possible embodiment of a machine 1 according to the invention. More precisely, the machine 1 is preferably used for processing the body of a blade intended for use, for instance, for the construction of a stage of a gas turbine. However, this is only a possible, and therefore not exclusive application of the machine 1 which could be used, for example, also for the finishing of surfaces of moulds or other workpieces which have surfaces with simple and/or double curvature.

The machine 1 comprises a CPU control unit (hereinafter simply referred to as CPU) which drives the first 10 and the second device 20 in such a way that the removal of material preferably takes place in a direction substantially normal to the three-dimensional surface 8. Basically, the CPU, based on a theoretical model of the three-dimensional surface 8, calculates the path to be followed by the tool 15 (or the sensor) and simultaneously controls the frame 21 and the product 5 so that this path is followed with the required condition of orthogonality. The control of the CPU is therefore carried out on the different degrees of freedom (or axes) assigned to the frame 21 and to the workpiece 5.

In the embodiment, the first device 10 configures two degrees of freedom for the workpiece 5, while the second device 20, in particular the support and movement assembly 25, configures four degrees of freedom for the frame 21 or for the head 22 connected to it by means of the clamping unit 30. Overall, therefore, the CPU exercises control over 6 different axes.

More precisely, the four degrees of freedom conferred to the head 22 correspond to three translation movements along three corresponding translation axes X, Y, Z and to a rotation movement around a first rotation axis (reference A). Again in the solution illustrated, the two degrees of freedom conferred to the workpiece 5 correspond instead to a rotation movement around a second rotation axis (reference B) and a further rotation movement around a third rotation axis (reference C), orthogonal to said second rotation axis.

In practice, the CPU drives the movement of the frame 21 along the translation axes X, Y, Z and around the first rotation axis A which preferably corresponds to one of the translation axes X, Y, Z. At the same time, the CPU drives the rotation of the workpiece 5 around the second rotation axis B and the third rotation axis C, orthogonal to each other, preferably selected in such a way as to be each parallel to a plane defined by two translation axes (for example the X-Y plane for the rotation axis B and the X-Z plane for the rotation axis C). The X, Y are indicated in figure 1.

In the embodiment in Figures 1 and 2, the frame 21 supports a head 22 whose configuration is best shown in Figure 6. The configuration of the frame 21 is instead better shown in Figure 3. Preferably, the frame 21 has a substantially L-shaped configuration defined by a first plate 211 and by a second plate 212 which extend on planes orthogonal to each other. The two plates 211, 212 are stably connected to each other. In order to ensure the necessary rigidity, reinforcing plates 213 are arranged between the two plates 211, 212 which also contribute to maintaining the perpendicular condition between the two plates 211, 212. The first plate 211 is connected to the support and movement assembly 25 which configures the movement axes of the frame 21. The head 22 is connected, by means of the clamping unit 30, to the second plate 212 on the internal side 212A thereof or on the side that forms a 90° angle with a corresponding side of the first plate 211.

Figure 5 shows a possible embodiment of an operating head 22 which comprises a base plate 220 in which a first portion 220A and a second portion 220B are identified, wherein the second portion 220 extends from the first portion 220A so as to impart to the base plate 220 a substantially L-shaped configuration. The base plate 220 comprises an internal surface 227A facing the clamping unit 30 (i.e. the internal side 212A of the second plate 212 of the frame 21) and an external surface 227B opposite to the internal surface 227A. A support element 225 is installed on said external surface 227B, projecting from the second portion 220B. Depending on the case, the support element 225 supports or defines a working point for a tool 15. Alternatively, the support element 225 may support a three-dimensional surface control sensor. Such a sensor, for example, may be of the laser type to perform a scan of the three- dimensional surface.

In the embodiment in Figure 5, the tool 15 is an abrasive wheel, but alternatively it could be in the form of an abrasive belt. On the external surface 227B there are installed rotation means 16-18-17-19 configured to carry out the rotation of the tool 15. In the solution visible in Figure 5, these means comprise a sliding roller 19 which configures the axis around which the abrasive wheel rotates. Said sliding roller 19 is rotatably installed at the cantilevered end 225A of the support element 225 and is integral in rotation with the abrasive wheel. Therefore, in this embodiment, the support element 225 supports the tool in proximity to its cantilevered end 225A.

The rotation means further comprise a driving pulley 18 driven by a motor 55 and a transmission belt 16 wound at least between the sliding roller 19 and the driving pulley 18. Preferably, the driving pulley 18 is installed on the first portion 220A, i.e. in a distal position from the cantilevered end 225 A of the support element 225. As better specified hereinafter, the driving pulley 18 is driven by an electric motor 55.

On the external surface 227B of the base plate 220 there is also installed a plurality of return rollers 17 which define a path for the movement and tensioning of the transmission belt 16. In this way, the rotation of the driving pulley 18 results in a rotation of the abrasive wheel.

If the tool consists of an abrasive belt, the latter is wound between the driving pulley 18 and the sliding roller 19 in a manner similar to that provided for the transmission belt 16. In this embodiment, the sliding element 19, and therefore the support element 225 define the working point of the abrasive belt (tool) in proximity to the cantilevered end 225A.

As mentioned in several points, instead of a finishing tool, the head 22 could support a sensor for controlling (reading) the three-dimensional surface 8 of the workpiece. This sensor could be installed on the external surface 227B or placed on the support element 225.

In another embodiment, the head 22 could support a nozzle for shot peening the three- dimensional surface 8 of the workpiece 5.

According to a preferred embodiment shown in the figures, the clamping unit 30 is constrained to the frame 21 and comprises first connection elements 31 configured to couple with second connection elements 32 integral with the head 22. The working position of the head 22 is defined following the coupling between each of the first connection elements 31 with a corresponding one of said second connection elements 32.

The clamping unit 30, when activated, firmly constrains the first connection elements 31 to the second connection elements 32. On the contrary, when the clamping unit 30 is deactivated, this constraint is lost so as to allow the removal of the head 22 and its replacement with another one provided with the tool necessary for the subsequent machining. According to a preferred embodiment, the first connection elements 31 are seats inside which the second connection elements 32 in the form of pins may be inserted. The clamping unit 30 comprises clamp closing means, preferably pneumatically operated, configured to act on said pins when they are inserted into the corresponding seats.

In particular, when the clamping unit 30 is activated, these closing means maintain the connection between the two parts (head 22 and frame 21) preventing any freedom of movement of the pins with respect to the corresponding seats. When the clamping unit 30 is deactivated, the head 22 may be removed by means of a translation movement which frees the pins from the corresponding seats.

According to a preferred embodiment, visible in Figure 5, the clamping unit 30 is installed on the internal side 212A of the second plate 212 of the frame 21. The clamping unit 30 comprises four first connection elements 31 or four seats each for receiving a corresponding pin integral with the operating head 22. The position of the clamping unit 30 is fixed, and therefore invariable, with respect to the frame 21. Therefore, also the first connection elements 31 maintain a fixed position with respect to the frame 21. This ensures the repeatability of the connection and positioning of the head 22. Ultimately, every time the head 22 is connected to the frame 21, the CPU can immediately determine the position of the tool 15B and consider this position as the machine zero position for the calculation of the trajectories. In the embodiment shown in Figure 5, the second connection elements 32 therefore comprise four pins which emerge from the internal surface 227 A of the base plate 220 of the operating head 22. In other words, the pins are defined on the surface opposite to that (external surface 227B) on which the rotation means 17-18-25-19 are installed which allow the rotation of the tool 15.

In particular, the second connection elements 32 emerge from a region of the internal surface 227 A corresponding to the second portion 220B.

According to a possible embodiment, the machine comprises a containment casing (not shown in the figures) removably connected to the frame 21 and adapted to contain the operating head 22.

According to a possible embodiment shown in the figures, the rotation means of the tool 15 are driven by a motor 55 (electrically operated) installed on the frame 21, preferably on the external side 212B of the second plate 212 (as visible in Figure 4). In particular, when the head 22 is connected to the clamping unit 30, or to the frame 21, the driving pulley 18 is connected to an output of the motor 55 through suitable coupling means. In this way, the connection of the driving pulley 18 to the motor 55 is simultaneous to the connection of the head 22 to the frame 21. The removal of the two connections at issue will therefore also be simultaneous.

In an alternative embodiment, the motor necessary for the rotation of the tool could be installed directly on the head, preferably on the external surface 227B where the rotation means 18-17-19-25 are installed.

In a possible embodiment (Figures 6 and 7), the frame 21 is configured to support a first operating head 22- A and a second operating head 22-B. Preferably, the two operating heads 22-A, 22-B have substantially the same configuration, differing in the structure and/or properties of the tool in terms of abrasive capacity. Basically, the two operating heads 22-A, 22-B will preferably be provided with different tools 15-A, 15-B or in any case configured to achieve different degrees of finishing on the three-dimensional surface 8 of the workpiece. In the embodiment shown in Figure 5, for example, each of the two operating heads 22-A, 22-B supports an abrasive wheel having a different degree from that of the other head. In an alternative embodiment, one or both tools could consist of abrasive belts. In another embodiment, one of the two heads could support a control tool or a nozzle for surface shot peening of the workpiece.

According to the principles of the invention, in this embodiment, a first clamping unit 30-A and a second clamping unit 30-B will be provided to allow the removable connection of the first operating head 22-A and the second operating head 22-B, respectively.

Preferably, the two clamping units 30-A, 30-B are installed on the internal side 212A of the second plate 212 of the frame 21 in a substantially specular position with respect to a reference plane containing the first rotation axis A of the frame 21 defined above. As can be seen in Figures 6 and 7, the two clamping units 30A, 30B may advantageously have the same configuration.

In this embodiment, a first motor and a second motor (not shown in Figures 6 and 7) will be provided to allow rotation of a first tool 15- A installed on the first operating head 22- A and of a second tool 15-B installed on the second head 22-B, respectively. Also in this case, the motors may be installed on the frame 21 or on the corresponding operating head 22- A, 22-B. With reference to the configuration of the operating heads 22-A, 22-B, in particular of the means provided to allow the rotation of each tool, reference is made to what has already been described above. However, it should be noted that in 6 and 7, the rotation means of the operating heads 22A-22B are indicated with the same reference numerals used for the head 22 of Figure 5 with the addition of the suffixes -A and -B, respectively.

In particular, in Figure 7 it may be seen that each of the two operating heads 22-A, 22-B comprises a plurality of pins 32-A, 32-B each of which is intended to be inserted inside a corresponding seat 31-A, 31-B defined by the corresponding clamping unit 30-A, 30-B.

The same technical solutions and the same considerations indicated above also apply with reference to the methods of connecting each operating head 22-A, 22-B to the frame 21. According to an embodiment shown in Figures 1 and 2, the machine 1 comprises also a reading sensor 88 for detecting the profile of the three-dimensional surface 8 of the workpiece 5. Such a sensor 88 is used, for example, to scan the three-dimensional surface 8 of the workpiece in order to reconstruct a “real model of the three-dimensional surface” . In the solution shown in the figures, the sensor is of the laser type and is installed so as to emerge on the external side 212B of the second plate 212. Therefore, depending on the operation to be carried out, finishing or reading of the surface, the CPU may suitably rotate the frame 21 around the first rotation axis A so as to make the tool 15 installed on the head 22 or the sensor 88 operative.

In each of the embodiments described above, the control of the operating status of the clamping unit 30 may be carried out directly by the CPU or by the same unit that controls the first device 10 and the second device 20. The possibility of activating/deactivating the clamping unit 30 also in other ways, for example through a remote control operated by an operator, falls within the scope of the present invention. In any case, the use of the clamping unit 30 advantageously allows automating the tool change operations, using for this purpose a manipulator (or a robotic arm) whose operation will be synchronized with that of the machine 1. In a possible actuation mode, the CPU will drive the frame 21 so that it reaches a tool change position, whereby the head 22 to be removed will be oriented in a certain way. Once the frame 21 has reached the position and orientation established for the tool change, the manipulator may hook the head 22 and, following the deactivation of the clamping unit, remove it from the frame 21. Subsequently, after having deposited the removed head 22, the same manipulator may couple another operating head to the clamping unit 30 which, once activated, will block the same head to the frame 21.

The present invention therefore also relates to an automated system for manufacturing a workpiece, in particular a turbine or compressor blade, comprising a machine 1 according to the above and a manipulator for removing the operating head from the frame 21 and preferably for connecting another operating head to the same frame 21.

The technical solutions adopted for the finishing machine allow fully fulfilling the set tasks and objects. In particular, the machine allows considerably speeding up tool change operations and at the same time makes the finishing operation feasible in a completely automated production line.

The machine according to the invention is subject to numerous modifications and variants, all falling within the scope of the inventive concept; moreover, all details may consist of other technically equivalent ones.

In the practice, the materials used as well as sizes and shapes may be any, according to the requirements and the prior art.