ITPD20110097A1 - DEVICE AND METHOD FOR SUPPORTING PARTS TO BE WORKED IN TRANSFER TYPE MACHINE MACHINES - Google Patents

Description

DEVICE AND METHOD FOR SUPPORTING PIECES TO BE WORKED IN TRANSFER-TYPE MACHINE TOOLS

The present invention refers to a support device for supporting workpieces to be machined in transfer type machine tools. The use of machine tools, called transfer machines, is known in the mechanical technology sector, in which there are a plurality of work stations, each of which is able to perform a different machining on a piece to be machined, in correspondence of which the latter is sequentially positioned by means of a movable table, for example of the rotating type.

To carry out each process, the transfer machines are equipped with special tool-holder spindles, equipped with feed devices, which allow the spindle to be moved in such a way that the tool comes into contact with the piece, once this is positioned in a specific station, to carry out the required processing.

The movable table for the translation of the pieces from one station to another is normally equipped with workpiece clamps that allow the piece to be fixed, so that it can move integrally to the table and be supported during the processing phases.

As a rule, the advancement of the tool does not exert a significant force on the piece and, consequently, it does not change the alignment of the moving table or of the piece subject to machining; therefore, even the alignment of the pieces subject to processing at the same time in the different stations does not undergo significant changes and the processing performed respects the required and established level of precision.

However, alignment problems can arise when the operations to be performed consist of â € œheavyâ € operations, such as broaching, which require a particular force to be exerted on the piece.

In such cases there is a concrete possibility that the force applied to the piece leads to a displacement both of the moving table as a whole and of the piece fixed to it and, as a consequence, machining defects also in the pieces being processed in the other stations.

Therefore, the technical problem underlying the present invention is that of providing a support device for processing pieces in transfer machines which allows to obviate the disadvantages mentioned above with reference to the known art. This problem is solved by the device for supporting workpieces in transfer type machine tools according to claim 1, by the machine tool according to claim 10 and by the method according to claim 11.

The present invention has some relevant advantages. The main advantage consists in the fact that the device according to the present invention allows to support the pieces that are processed in transfer machines in such a way that, even in the heaviest processing, the risk of misalignment of the piece on the moving table is limited. In this way, the positioning of the piece remains precise and constant even for subsequent processing.

Other advantages, characteristics and methods of use of the present invention will become evident from the following detailed description of some embodiments, presented by way of non-limiting example. Reference will be made to the figures of the attached drawings, in which:

Figures 1 to 4 are sectional side views of a support device according to the present invention, during different operating phases;

Figures 1A to 4A are side views in detail, in section, of the device according to the present invention, respectively in the operating steps of Figures 1 to 4; And

- figure 3B is a cross-sectional view of a detail of the device according to the present invention, in the operating configuration of figure 3.

With reference initially to Figure 1, a support device, suitable for carrying out the support of a workpiece P in a transfer type machine tool, is generally indicated with the number 100.

The device 100 is mounted on a mandrel M of a known type, on which it engages at a connection end 101, and comprises a base body 10, preferably formed by a head portion 10 'and a portion of base 10 ''.

The device comprises a support element 1, substantially made by means of a movable cylinder, supported in the head portion 10 'by means of a stiffening element 3, which will be better illustrated below.

The support element 1 is at least partially retractable in the body 10, so that a support end 11 remains defined, protruding from the head portion 10 '. The configuration of the device is such that the support end 11 can be moved by moving the spindle M, to come into contact with the workpiece P.

In greater detail, the support element 1 is inserted in a special seat defined in the stiffening element 3 and, in an initial operational phase, is free to move inside the seat, in particular along a direction defined by the axis of the cylinder which forms the support element 1. Consequently, the support end 11 will be able to approach / move away from the head portion 10 '.

As can be observed in figure 1, this movement is opposed by means of return means 2, in particular made by means of a helical spring, arranged at the base of the stiffening element 3. In this way, when the support element 1 is recalled towards the base body 10, for example due to the action of a reaction force that is generated when it is pushed against the piece P, the return means 2 oppose the movement of the support element 1 at least in the direction of callout R, illustrated in figure 2, of the support element 1.

As will be illustrated in greater detail below, the support element 1 has the function of supporting the piece P during machining, in particular supporting it on the side opposite to the machining one, in order to support the stresses produced during machining and avoid that these modify the alignment of the piece P, producing machining errors even in the subsequent stations of the transfer machine.

In order to carry out this support function, during the processing steps, the support element 1 is arranged to rest on the piece P and, to ensure that this occurs in a precise manner, the device according to the present invention provides for moving the spindle M which supports the device 100 towards the piece P for a distance d greater than the nominal one dN, that is the one that separates the support end 11 from the piece P when the spring is at rest. In this way, as can be seen in figure 2, the support end 11 will surely come into contact with the piece P regardless of any surface irregularities or positioning defects of the piece P, as these will be compensated by the displacement of the spindle greater than the nominal distance dN.

In this regard, the spring 2 advantageously has a low elastic constant, thus generating a negligible return force with respect to the forces developed during the machining of the piece P.

Once the device has been brought into the working position, illustrated in figure 2, the stiffening element 3 allows the support element 1 to be rigidly locked with respect to the body 10, in order to support the forces that arise. following the action of the tool on the piece P.

In greater detail, the stiffening element 3 defines locking means 3 of the support element 1, which selectively allow the movement of the support element 1 with respect to the body 10 during the steps of approaching the device 100 to the piece to be machining P, as previously illustrated, and blocking element 1 during the machining phases.

In the present embodiment, the locking means 3 and the element 1 are made by means of a hydraulic stiffener of the Roemheld® type, in which the movable body, which defines the element 1, slides inside the corresponding body cylindrical, which in turn defines the stiffener 3, can be locked following the application of at least a predetermined pressure in correspondence with the actuation portion 31.

Again by way of example, as an alternative to the Roemheld® stiffener, a Kostyrka® bush can also be used, in which to house the support element 1, the operation of which is however known to a technician in the sector.

The presence of the element 1 supporting the piece P during its processing, according to the configuration illustrated in figures 2 to 4, kept in a fixed position through the use of the locking means 3, therefore allows to support in an optimal way the piece P, preventing it from moving during processing or from moving with respect to the movable table of the transfer machine, the latter not being shown in the figure.

Furthermore, the support element 1 in contact with the piece P allows to limit the vibrations that are created during the machining, with a consequent improvement in the functioning and duration of the transfer machine as a whole, as well as a better quality of the machining. itself.

In the following, and with reference to Figures 2 to 4, the operation of the locking means 3 is described, with particular reference to their actuation following the reaching of the working position by the support element 1.

As previously mentioned, the device 100 is positioned with the support end 11 in contact with the piece P before starting its machining.

Once this position has been reached, described in figure 2, the support element 1 is locked by means of the locking means 3 and the machining of the piece P begins.

The stiffener 3 is locked by means of a special hydraulic circuit which allows an operating fluid FO to reach the actuation portion 31, which corresponds to an annular surface of the stiffener which is wetted through a respective chamber. In the operating condition of Figure 2, the operating fluid which wets the actuation portion 31 is at low pressure and, therefore, the support element is free to move. Again in this operating configuration, the only force exerted on the fluid is that of the spring 81 of the compensation element.

The device 100 comprises a collection chamber 5 for the operating fluid FO, which is in communication with the aforementioned actuation portion 31 through an operating conduit 51.

In addition, the collection chamber 5 is also in communication with a compensation chamber 7 through a compensation duct 71, to which the fluid enters through a passage 41 which can be selectively open or closed, according to methods that will be exposed below. .

One of the walls that form the compensation chamber 7 is defined by the end of a compensation piston 8, through whose movement it is possible to vary the dimensions of the compensation chamber 7 and, consequently, to compensate for the volumetric variations of the chamber collection 5 and any micro leaks of FO fluid due to micro-leaks, as will be seen below.

The device further comprises a piston-type shutter member 4, which is formed by a movable plate with an elongated central portion 40 and a crown 42 which surrounds it. An elongated terminal 50 of the hydraulic circuit is housed in the elongated central part of the hollow 40, in which the ducts 51 and 71 are formed. The seal can be made, for example, by means of O-rings 52.

In rest conditions, ie without being subjected to external forces, as illustrated in figure 2, the shutter member 4 is kept at a distance thanks to the springs 55 from a support base 53 of the elongated terminal 50, so that a end 54 of the terminal 50 is kept at a distance from the bottom 43 of the cavity made in the elongated central part 40 of the obturator member, so as to define the collection chamber 5.

It can therefore be understood how the movement of the obturator element 4 allows to vary the volume of the collection chamber 5. As previously mentioned, this variation, when the passage 41 is open, can be compensated by the compensation piston 8.

In fact, with the passage 41 open, when the pressure in the hydraulic circuit increases as a result of the decrease in the volume of the collection chamber 5, there is an increase in pressure also in the compensation chamber 7, which produces a displacement of the compensation piston 8 such to increase the volume of said compensation chamber 7 and to keep the pressure in the hydraulic circuit substantially constant. More precisely, it is possible to appreciate a not very significant generalized pressure increase in the circuit, proportional to the reaction force of the spring 81 of the compensation device, which in any case can be considered negligible from the point of view of the operation of the present device.

It should be noted that, similarly, the presence of the compensation piston is also advantageous for the purpose of compensating for any variations in the quantity of the operating fluid FO that could occur due to leaks or additions during maintenance of the device.

For this purpose, the compensation piston 8 advantageously comprises a spring 81, or other similar elastic return means, which allows the end of the piston 8 to be kept in contact with the fluid inside the compensation chamber 7 even when following a change in the level of the operating fluid FO in the same or a different positioning in the space of the device 100 (horizontal, vertical or otherwise inclined).

The passage 41 is defined by means of a groove in the internal lateral surface of the cavity in the elongated central part 40 which connects the duct 71 and the collection chamber 5, at least in the operating configuration at rest illustrated in Figure 2.

However, the groove has such dimensions that, when the volume of the collection chamber 5 is decreased beyond a predetermined level, following the displacement of the shutter member 4, the passage 41 is closed, obstructed by the lateral surface of the elongated terminal 50 . In this way, the obturator member 4 can selectively allow communication between the collection chamber 5 and the compensation chamber 7, through the duct 71 and the passage 41, or close this last passage, preventing communication with the compensation chamber 7 and the consequent compensation of the pressure in the hydraulic circuit. It should also be noted that the elongated terminal advantageously has a tapered final part 56 which, when facing the passage 41, allows the operating fluid FO to flow out.

When the passage 41 is closed, an increase in pressure in the collection chamber 5, due in the present case to a decrease in the volume of the chamber itself, is transmitted through the duct 51 to the activation portion 31, thus allowing the activation of the stiffener 3 and the consequent locking of the support element 1.

This function can be achieved by means of the shutter member 4, which, approaching the support base 53, reduces the volume of the collection chamber 5, initially closing the passage 41 and subsequently, increasing the pressure in the hydraulic circuit defined by the duct 51, until stiffener 3 is locked. This direction, illustrated in figures 3 and 4, will be indicated as the actuation direction A.

As can be seen in the figures, the movement of the shutter member 4 is opposed by return means 55, made by means of springs, which tend to draw the shutter member 4 towards a position of maximum extension of the collection chamber 5, which substantially coincides with the end point of the shutter member 4 with respect to the elongated terminal 50. Consequently, when the shutter member 4 is moved in the direction of actuation A, bringing it closer to the support base 53 and closing the chamber collected 5, the springs 55 tend to return it to the starting position. Also in this case, the springs 55 have a low elastic constant, that is of such an entity that the forces involved following the compression of the springs are negligible compared to the force with which the actuator member 4 is actuated in order to achieve activation of the stiffener 3.

The different operating configurations of the device are illustrated respectively in Figures 2 to 4. More precisely, in Figure 2, the shutter member 4 is located in correspondence with its first end-of-stroke position, that is the one in which the collection 5 has maximum size. In this configuration, as can be seen from figure 2A, the passage 41 is open, and communication with the clearing chamber 7 is allowed. With reference to figure 3, when the shutter member 4 begins to be moved in the direction of actuation A, i.e. that of closing the collection chamber 5 and approaching the base support 53, an operating configuration is defined in which the passage 41 is closed, preventing communication with the compensation chamber 7, as previously described . The further movement of the shutter member 4 in the direction of actuation A, as illustrated in figure 4, further closes the collection chamber 5 and causes an increase in the pressure of the operating fluid in the hydraulic circuit, since the compensating action of the piston 8. This increase in pressure is transmitted to the activation portion 31, locking the support element 1.

Advantageously, the actuation of the shutter member 4 can be achieved by exploiting the tool cooling / lubrication emulsion of the machine as the activation fluid FA of the shutter member.

In fact, the connection end 101 is in communication with the supply duct 60 of the spindle for the tool cooling / lubrication emulsion which can thus be introduced into an actuation chamber 6. The chamber 6 extends for a surface substantially equal to the overall surface of the shutter member 4, formed by a front face of the hollow elongated central portion 40 and by a ring-shaped surface of the crown 42 which extends concentric to the central portion 40. As can be seen in Figure 3 , and in particular in Figure 3B, the actuation chamber 6 is divided into two volumes 6 'and 6' 'respectively arranged in correspondence with the front face and the ring surface, connected to each other through passages 61 made at the perimeter surface of the housing for the elongated central portion 40 made in the connection end 101 to the mandrel M.

It can be immediately observed that the overall surface of the shutter member 4 subject to the pressure of the actuation fluid FA has a greater extension than the surface subject to the pressure of the operating fluid FO. The obturator member 4 is therefore subject on the one hand to the force exerted by the pressure of the operating fluid FO on the surface defined by the bottom 43 of the cavity of the central hollow portion 40 and on the other side to the force exerted by the operating pressure FA on the surfaces facing the volumes 6 'and 6' 'described above. Normally, the liquid FA is not under pressure in the volumes 6â € ™ and 6â € and, therefore, only the forces of the springs 55 act on the shutter element 4, keeping it at the maximum distance from the support base 53, in a condition of equilibrium. When the pressure in the actuation chamber 6 is increased, in particular following the introduction of the actuation fluid FA, the obturator member 4, being the force exerted by the fluid FA decidedly higher than that exerted overall by the group of antagonist springs 55, will tend to return to a new equilibrium position, moving in the direction of actuation A. The displacement therefore decreases the volume of the collection chamber 5 initially closing the passage 41 and, subsequently, increasing the pressure inside the chamber 5 until a that the force exerted by this is equal to that exerted by the pressure exerted by the actuation fluid FA in the actuation chamber 6.

Consequently, the greater extension of the surface on which the pressure of the operating fluid FA acts compared to that of the surface on which the pressure of the operating fluid FO acts, allows the operating fluid FO to be brought to high pressures, through the action of the low pressure FA drive fluid. To obtain the necessary pressure to activate the stiffener 3, it will be sufficient to size the components appropriately, in particular in relation to the size of the surfaces in play and the stroke of the organ 4.

It is evident that, although this embodiment solution is particularly advantageous as it exploits the emulsion already normally used for other purposes in transfer machines, different means for activating the locking means, such as for example electromechanical or pneumatic systems, can also be provided.

In addition to the components described above, the device 100 comprises safety valves 62, 72, respectively connected to the actuation chamber 6 and to the compensation chamber 7. The valves are calibrated differently, in particular the safety valve 62 will be calibrated in so that the chamber 6 does not reach too high a pressure, potentially capable, thanks to the multiplication factor, of making the fluid FO reach pressures such as to damage the Kostyirka device or any other type of stiffening element that may be present.

The safety valve 72, on the other hand, will be calibrated so that any excess volume of FO fluid introduced during the filling phase of the device does not create overpressures in the chamber 7 potentially harmful to the compensation device.

In addition, there is also a plug 57 for filling / bleeding the fluid circuit FO, communicating with the chamber 5. It is therefore evident that the support device 100 allows to solve the problems identified with reference to the present invention, thanks to the support function carried out by element 1, able to position itself in perfect adherence with piece P, without altering its position with respect to an ideal work surface even during the heaviest machining operations and without exerting significant forces on it which could alter its position.

The characteristics of the device allow this adhesion to be maintained even in cases in which the advancement of the support device exceeds the height of the external surface of the piece to be machined P or in the case in which the external surface of the piece is not perfectly flat and therefore the meeting of this surface with the support surface is not perfectly matching. Furthermore, by providing a movement for a distance d greater than the nominal one dN, it is avoided that this is stopped before it meets the external surface of the piece. In addition, a further advantage is represented by the fact that the device is engaged on one of the spindles of the transfer machine, like a normal tool, without requiring special equipment or modifications to the machine, and by the fact that it uses the cooling fluid and the relative pressure for its operation.

It must also be noted that, in order to avoid that the stress produced by the tool that is to be counteracted is directly applied to the ball bearings of the spindle, that is to say on the rotating part of the spindle M where the device is mounted, the element 101 can be supported floating along the axis of the device 1, without being firmly integral with the element 10 ''.

On the contrary, thanks to this construction configuration, the latter will completely absorb the effort produced by the machining to be counteracted, discharging it in turn onto the outer body of the mandrel M, that is to say onto the solid outer jacket of the same.

Claims (13)

CLAIMS 1. Support device (100) for supporting workpieces (P) in transfer type machine tools, comprising: - a base body (10) which can be engaged on a mandrel (M); a support element (1) at least partially retractable in said body (10) and comprising a support end (11) able to be arranged in contact with the workpiece (P) by means of a relative movement between the device (100 ) and the workpiece (P); - return means (2) adapted to oppose the movement of said support element (1) at least in a return direction (R) towards said base body (10); - locking means (3) of said support element (1) adapted to selectively allow the movement of said support element (1) with respect to said body (10) during a phase of approaching the workpiece (P) and the locking of said support element (1) during a working step. Support device (100) according to claim 1, wherein said locking means (3) are of the hydraulic type and are connected to a hydraulic circuit of an operating fluid (FO), in such a way that said locking means ( 3) block said support element (1) along said return direction (R) when said operating fluid (FO) reaches a predetermined pressure. Support device (100) according to claim 2, comprising a collection chamber (5) for said operating fluid and an obturator member (4) adapted to act on said operating fluid (FO) in the collection chamber (5) to increase the pressure. Support device (100) according to claim 3, in which the movement of said shutter member (4) in an actuation direction (A) is adapted to decrease the volume of said collection chamber (5), in a manner to increase the pressure of said operating fluid (FO). 5. Support device (100) according to claim 3 or 4, in which said collection chamber (5) is in communication, through a selectively reclosable passage (41), with a compensation chamber (7) to compensate for variations in volume in said collection chamber (5). Support device (100) according to claim 5, when dependent on claim 4, wherein an initial movement of said shutter member (4) in said actuation direction (A) closes said passage (41). Support device (100) according to one of the preceding claims, wherein said collection chamber (5) is defined by a first surface of the shutter member (4), the device (100) further comprising an actuation chamber (6) adapted to house an actuation fluid (FA), said actuation chamber (6) being defined by a second surface of said shutter member (4) which has a greater extension than said first surface. Support device (100) according to one of the preceding claims, wherein said driving fluid (FA) is a cooling emulsion supplied through the mandrel (M). Support device (100) according to claim 1 or 2, wherein said locking means are made by means of a stiffening element (3). 10. Machine tool of the transfer type comprising a movable table, a plurality of work stations and a plurality of spindles (M), said movable table being provided with means for fixing a piece to be worked (P) and adapted to move the piece to be machined (P) at each of said work stations, and characterized in that it further comprises at least one support device (100) according to one of claims 1 to 9 mounted on at least one of said mandrels (M). 11. Method for supporting workpieces in transfer type machine tools, includes the steps of: to. providing a support element (1) movable with respect to the workpiece (P) and retractable towards a base body (10); b. advance said support element (1) towards the workpiece (P) for a distance (d) greater than a nominal distance (dN) which separates said support element (1) from the workpiece (P), so that a resting surface (11) of said support element (1) comes into contact with the workpiece (P) and said support element (1) is drawn at least partially towards the base body (10); c. locking said support element (1) with respect to said base body (10). Method according to claim 11, wherein said step of locking said support element (1) is carried out by locking means (3) operated by an operating fluid (FO) and comprising a further step of varying the pressure of said operating fluid (FO), in such a way that said locking means (3) block the support element (1) when a predetermined pressure is reached. Method according to claim 11, wherein said step of varying the pressure of said operating fluid (FO) is accomplished through a further step of providing a driving fluid (FA) at an operating chamber (6), the filling of said actuation chamber (6) with said actuation fluid (FA) being such as to move an obturator member (4) in such a way as to decrease the volume of a collection chamber (5) and increase the pressure of the operating fluid contained therein.