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Title:
TOOL-HOLDING DEVICE
Document Type and Number:
WIPO Patent Application WO/2012/011058
Kind Code:
A1
Abstract:
Tool-holding device suitable for being coupled to a mandrel of a machine tool or a mandrel fitted on a robot, comprising: - one or more tool-holder carriages (10); such carriages are positioned radially in relation to the mandrel axis (X) and are able to support a respective attachment group of a tool; - a carriage-holder head (30) on which the three carriages are housed and comprising a command actuator (32) for each carriage; each command actuator (32) is operatively connected to a respective carriage (10) and can be fed by a feed device to move said carriage radially between a rearward position and a forward position; - a connection body (50, 500) which can be coupled to the mandrel of the machine tool and provided with distribution means to draw said feed device to the command actuators (32), wherein the translation axis of each carriage (10) coincides substantially with the main axis of the respective command actuator (32) in the radial direction.

Inventors:
BALOTELLI, Giuseppe (Via Due Muri, 10 Concesio, BRESCIA, I-25060, IT)
Application Number:
IB2011/053227
Publication Date:
January 26, 2012
Filing Date:
July 20, 2011
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BALOTELLI, Giuseppe (Via Due Muri, 10 Concesio, BRESCIA, I-25060, IT)
International Classes:
B23B31/30; B21D22/14; B21H3/08; B23B29/034; B23B31/16; B23C3/00; B23C3/02; B23G5/12; B23G5/16; B23Q5/04
Domestic Patent References:
Foreign References:
US20050166727A1
US20080157487A1
DE3408352A1
DE9210613U1
US20030222415A1
DE10160031A1
DE3237587A1
US4388818A
DE4428049A1
DE19845948A1
US20030102640A1
US20030156913A1
Other References:
None
Attorney, Agent or Firm:
CHIMINI, Francesco et al. (Piazza della Vittoria 11, Brescia, I-25122, IT)
Download PDF:
Claims:
Claims

1. Tool-holding device suitable for being coupled to a mandrel of a machine tool or a mandrel fitted on a robot, comprising :

- one or more tool-holding carriages (10) positioned radially in relation to the mandrel axis (X) and able to support a respective attachment group of a tool or gripping jaw of a piece;

- a carriage-holder head (30) on which the carriages are housed and comprising a command actuator (32) for each carriage, each command actuator (32) being operatively connected to a respective carriage (10) and being fed by a feed device to move said carriage radially between a rearward position and a forward position,

- a connection body (50; 500) which can be coupled to the mandrel of the machine tool and provided with distribution means to bring said feed device to the command actuators (32), wherein

the translation axis of each carriage (10) coincides substantially with the main axis of the respective command actuator (32) in the radial direction.

2. Device according to claim 1, comprising a plurality of carriages angularly equidistant from each other.

3. Device according to claim 1 or 2, wherein each command actuator (32) is a cylinder, preferably hydraulic, comprising a piston (34) oriented radially in relation to the axis of the mandrel and an outer sleeve (36) defining with the piston an anterior chamber (37) and a posterior chamber (38) of the cylinder, where said piston is integral with the carriage-holder head (30) and where said sleeve (36) is movable radially in relation to said piston between a rearward position and a forward position, said sleeve forming the body of the tool-holder carriage ( 10 ) .

4. Device according to claim 3, wherein the command actuators are housed in respective radial seats (39) made in the carriage-holder head (30) .

5. Device according to any of the previous claims, wherein the command actuators (32) have a substantially prismatic or cylindrical shape and have a front portion (33) projecting axially from the front surface of the carriage-holder head.

6. Device according to claim 5, wherein the tool-holder carriages (10) are axially held to the carriage-holder head (30) by containment gibs (11), said gibs (11) axially engaging the part of the front surface of the carriages aligned with the front surface of the carriage- holder head (30) .

7. Device according to any of the claims from 2-6, wherein the sleeve (36) of the hydraulic cylinder is closed at the distal end by a closure plate (39) , said closure plate (39) projecting frontwards in relation to the front surface (33) of the carriages so as to allow the attachment of a screw to adjust the radial position of a tool attachment group mounted on a respective carriage .

8. Device according to claim 7, wherein said closure plate (39) further supports adjustment nuts co-operating with an abutment surface made in the carriage-holder head (30) to determine the inward stroke of the carriage, and a further adjustment screw co-operating with a fork attached to the carriage-holder head (30) to determine the outward stroke of the carriage.

9. Device according to any of the claims from 2-8, wherein in the piston (34) of each cylinder there is a first feed hole (41) coming out in the rear chamber (38) of the cylinder and a second feed hole (42) coming out in the front chamber (37) of the cylinder, said feed holes being in fluidic communication with respective feed ducts (43, 44) made in the connection body (50; 500).

10. Device according to claim 9, wherein the piston (34) of each hydraulic cylinder is detachably fixed to the carriage-holder head (30) and assembled to said head in two different positions so as to change over the fluidic connection from the feed holes (41, 42) of the piston to the feed ducts (43, 44) in the connection body.

11. Device according to any of the previous claims, wherein the connection body (50) has a conical shape and has a proximal end (51) coupling with the tie-rod of a mandrel with a hollow shaft having a conical seat, and wherein at least one feed duct (43) comes out in said proximal end so as to be placed in fluidic communication with a corresponding feed passage made in said mandrel.

12. Device according to any of the claims from 2-10, wherein the connection body (500) has a substantially cylindrical shape and comprises a proximal end (501) coupling to a rotation shaft.

13. Device according to claim 12, wherein around said connection body (500) a feed unit (503) is mounted with the interposition of roller devices (502), which can be connected to the feed ducts of the command fluid and in which feed passages (505, 506) are made in fluidic communication with the feed ducts (43, 44) of the connection body.

14. Device according to claim 12 or 13, wherein said proximal end (501) of the connection body is able to place the feed passages made in a perforated rotation shaft in fluidic communication with the feed ducts inside the connection body (500).

15. Device according to any of the claims from 12-14, wherein there is at least one further pressurisation and/or lubrication passage (45) in the connection body (500) which can be supplied with a pressurised fluid to clean and/or lubricate the tool-holding device.

16. Tool-holding device according to any of the previous claims, comprising at least two carriages (10) each bearing a gripping jaw to obtain a gripping or blocking group of a piece.

17. Tool-holding device according to any of the previous claims, comprising a synchronisation system (80) of the radial movement of the tool-holder carriages (10), said synchronisation system (80) comprising a synchronisation disc (82) fitted idle to the connection body (50; 500) , behind the carriage-holder head (30), said synchronisation disc (82) bearing a plurality of levers (84), each having a fixed pin (86) constrained to the disc (82) and a mobile pin (88) engaging in the body of a respective carriage and passing through a slot (90) made in the rear wall of the carriage-holder head (30) . 18. Processing unit comprising a tool-holding device according to any of the previous claims, wherein on at least one tool-holder carriage of said device a motorized tool is fitted, for example fitted with a bur for the realization of channels or at least one cutting edge for the realization of polygonal surfaces.

19. Processing method of a piece to obtain a threading having a pitch "P" and a depth greater than that which can be achieved in a single work cycle with the cutting edge of a tool, comprising the steps:

- to fit to a tool-holding device according to any of the claims from 1-15 a number "n" of two or more tools, each on a respective carriage, so that said tools are angularly distanced from each other by an angle of 360°/n and axially staggered by a height of P/n;

- to radially draw up a first carriage to the surface to be threaded and command the mandrel so that the relative first tool performs a threading having a depth equal to the cutting edge of the tool;

- to radially draw up the further tools to the piece to be threaded, in sequence, making each tool complete a progressively greater radial stroke than the tool which preceded it, so that each tool removes further shavings than the one before;

- at the end of the processing performed by the last tool, to radially and contemporarily distance all the carriages from the processed piece and draw back the tool-holding device to the starting position, without moving back over the threading made.

20. Processing method of a piece to obtain a threading having a pitch "P" comprising the steps: - to fit to a tool-holding device according to any of the claims from 1-15 a number "n" of two or more tools, each on a respective carriage, so that said tools are angularly distanced from each other by an angle of 360 °/n and axially staggered by a height of P/n;

- to fit to said tool-holding device at least one fixed, that is radially immobile, tool;

- to command a mandrel so that the fixed tool performs a threading of the desired depth on a piece to be threaded;

- having reached the desired depth, to radially draw up one or more carriages to the surface to be threaded to make a channel of the thread; and

- to command the return of the mandrel to disengage the tool-holding device from the piece.

21. Method according to claim 20, wherein the step of commanding the return comprises a step of conveying the threading shavings outside the cavity defined by the thread.

Description:
DESCRIPTION

"Tool-holding device"

[0001] The present invention relates to a tool-holding device which can be coupled to the mandrel of a machine tool, in particular to perform radial processing on a piece, in other words achieved by shifting a tool radially in relation to the mandrel axis.

[0002] A particular example of such a tool-holding device is known as "recess" or "recessor" inasmuch as suitable for performing processing in undercut on a piece.

[0003] Currently, various solutions are known of for achieving a radial shift of a tool fitted on a tool- holder carriage.

[0004] A first solution envisages a unit fitted with a lever system, actuated by a piston placed in a rear part of the unit, parallel to the mandrel axis.

[0005] Another solution envisages the use of a cone as the actuator means which, by axially shifting, causes a radial shift of the tool-holding carriage.

[0006] Yet another solution envisages the use of a rack gear which transforms the axial movement of an actuator into the radial movement of the tool.

[0007] All these solutions have in common the fact that the axial movement of the actuator device is transmitted to the tool by means of transfer means. This transfer of the movement is however the source of significant drawbacks.

[0008] In particular, the specific pressure exerted by the command actuator is not transferred directly onto the carriage-holder device, but through the transfer means. In other words, the stress generated by the command actuator causes the onset of vibrational phenomena which jeopardises the quality of the processing performed by the tool.

[0009] In addition, such vibration phenomena cause precocious wear of the processing tool and of the transfer means, especially in the case of processing steel .

[0010] The purpose of the present invention is to propose a tool-holding device able to overcome the drawbacks mentioned above.

[0011] Such purpose is achieved by a tool-holding device according to claim 1. The dependent claims describe preferred or advantageous embodiments of the invention.

[0012] The characteristics and advantages of the device according to the invention will be more clearly comprehensible from the description given below of its preferred embodiments, given by way of a non-limiting example with reference to the attached drawings, wherein:

[0013] - figure 1 shows a perspective view of the tool- holding device according to the invention, in one embodiment ;

[0014] -figure 2 shows the device seen from the side;

[0015] -figure 3 shows the device seen from behind;

[0016] -figure 4 shows a front view of the device;

[0017] -figure 5 is a longitudinal cross-section of the device along the line A-A in figure 4;

[0018] - figure 6 shows, in longitudinal cross-section along the line D-D in figure 4, the tool-holding device connected to a mandrel with a hollow shaft which controls the rotation of the device;

[0019] -figures 7-12 are similar views to the previous of a tool-holding device in an embodiment variation;

[0020] -figure 13 shows, in axial cross-section, a tool- holder carriage fitted with means of adjustment of the stroke and to which a tool-holding group is fitted;

[0021] -figures 14-24 show examples of processing a piece which can be performed with the tool-holding device according to the invention;

[0022] -figure 25 is a perspective view of a tool-holding device in a further embodiment;

[0023] -figure 26 shows the device of the previous figure, to which three tools for processing a piece have been fitted;

[0024] -figure 27 is a perspective view of a tool-holding device, in an embodiment which provides for the use of mechanical means of synchronising the movement of the tool-holder carriages;

[0025] -figure 28 shows an axial cross-section of the device in figure 27;

[0026] -figures 29 and 30 show a rear and partially transparent view of the device in figures 27 and 28, with the carriages respectively in a rearward and forward position

[0027] -figure 31 is an axial cross-section of the device with synchronisation means, in an embodiment variation.

[0028] In said drawings, reference numeral 1; 100 globally denotes a tool-holding device suitable for being coupled to a mandrel 200 of a machine tool.

[0029] Later in the description, the elements common to the various embodiments of the tool-holding device will be indicated using the same reference numerals.

[0030] Later in the description, axial direction is understood to mean the direction parallel to the rotation axis X of the mandrel of the machine tool and radial direction a direction orthogonal to the axial direction X.

[0031] In addition, the terms "front" or "anterior" will be used to indicate an element axially facing the piece to be processed, that is on the side opposite the mandrel of the tool-holding device. Said mandrel therefore couples to the "rear" part of the tool-holding device.

[0032] In one general embodiment, the tool-holding device 1; 100 comprises at least one tool-holder carriage 10 arranged radially in relation to the mandrel axis X. Preferably, as will be described below, the tool-holding device comprises a plurality of tool-holder carriages 10, for example three, angularly equidistant from each other. In other words, said carriages 10 are positioned along a circumference with its centre along the mandrel axis X and distanced from each other by an angle equal to 360°/n, where n is the number of carriages. Each tool- holder carriage 10 is suitable to support a respective tool; such latter may be a single or multiple tool.

[0033] The carriages 10 are fitted on a carriage-holder head 30. Said head comprises a command actuator 32 for each tool-holder carriage 10. For example, the carriage- holder head 30 has a substantially cylindrical structure, with rotation axis coaxial to the mandrel axis X.

[0034] Each command actuator 32 is operatively connected to a respective carriage 10 and is fed by a feed device to move said carriage 10 radially between a rearward position and a forward position.

[0035] The feed device is drawn to the three command actuators 32 by a connection body 50; 500 which extends rearwards from the carriage-holder head 30 to be coupled to the mandrel of the tool-holding device. The connection body 50; 500 is provided with distribution means to draw the feed device to the command actuators 32.

[0036] Innovatively, the translation axis Y of each carriage 10 coincides substantially with the main axis of the respective command actuator 32 in the radial direction. In other words, a radial axis may be associated with each command actuator 32 along which the action exerted by the actuator to move the carriage 10 between the rearward and forward position is concentrated. Similarly, a main axis Y is associated with each carriage, along which the carriage moves. According to the invention, the action exerted by each actuator 32 is coaxial to the respective carriage 10. Consequently, each carriage is directly connected to a respective command actuator and no return means transmitting the movement of the actuator to the carriage are provided.

[0037] In a preferred embodiment, each command actuator 32 is a cylinder, preferably a hydraulic cylinder, and the feed device is a command fluid, such as oil. Each cylinder 32 comprises a piston 34 oriented radially in relation to the mandrel axis X and an outer sleeve or lining 36 defining with the piston 34 an anterior chamber 37 and a posterior chamber 38 of the cylinder. [0038] Innovatively, each piston 34 is integral with the carriage-holder head 30 while the sleeve 36 is movable radially in relation to said piston 34 between a rearward position and a forward position. Advantageously, the sleeve itself 36 forms the body of the tool-holder carriage 10. In other words, each carriage 10 is part of the cylinder by which it is commanded to translate. Consequently, later in the description, except as otherwise indicated, the term "cylinder sleeve" and the term "carriage" are used to indicate the same functional element and are interchangeable terms.

[0039] According to one embodiment, the command actuators 32 are housed in respective radial seats 19 made in the carriage-holder head 30. Preferably, moreover, the command actuators 32 have a substantially prismatic or cylindrical shape and have a front portion 33 , which is also the front part of the relative carriages 10, for example projecting axially from the front surface of the carriage-holder head 30. An attachment group of a tool 300 is suitable to be fixed to a said front portion 33 (figures 13-24, 26) .

[0040] In one embodiment, the tool-holder carriages 10 are axially held to the carriage-holder head 30 by containment gibs 11. Said gibs 11 axially engage the part of the front surface of the carriages aligned with the front surface of the carriage-holder head 30. Consequently, said gibs 11 extend along the sides of the projecting front portion 33 of the carriages. In the embodiment example shown, with three carriages, three containment gibs 11, each having a "V" shape forming an angle of 120°, are fixed to the carriage-holder head 30. Each gib 11 therefore axially engages two adjacent portions of a pair of carriages 10.

[0041] Advantageously, moreover, a front protection plate 15 is fixed to the containment gibs 11 suitable to prevent dirt from penetrating inside the carriage-holder head 30. For example, in the inner surface of said protection plate 15 dirt-proof gasket housing channels are made which abut with the front surface of the carriages so as to block the entry of foreign bodies during the radial movement of the carriages.

[0042] Returning to the structure of the carriages, in one embodiment the sleeve 36 of the cylinder is closed at the distal end, peripheral in relation to the mandrel axis X, by a closure plate 39. Said closure plate 39 projects frontwards in relation to the front surface 33 of the carriages so as to permit the attachment of a tool adjustment screw 40, that is an adjustment screw of the tool-holder support, to adjust the radial position of the tool attachment group 300. [0043] In one embodiment, such tool attachment group 300 is fixed to the carriage 10 by screws which are axially screwed into corresponding threaded holes 33' made in the projecting front portion 33 of each carriage. The attachment screws of the tool attachment group 300 to the carriage pass through slots which permit the radial adjustment of the position of the group. Such radial adjustment is performed by means of the tool adjustment screw 40 supported in a radial position by the closure plate 39 of each cylinder.

[0044] Such possibility of radial adjustment of the assembly position of the tool attachment group 300, which can be combined with the possibility of radial adjustment of the assembly position of the tool on the relative attachment group, makes the tool-holding device extremely versatile in that, for the same carriage stroke, if the tools are assembled in different radial positions a combination of the processing performed by each on the piece can be achieved. In particular, as will be described further below, the front processing surface of the piece (facing) can be summed to triple compared to the stroke of the individual carriages. By using multiple tools, such summing effect of processing can be multiplied even further.

[0045] Advantageously, the tool-holding device also permits adjustment of the stroke of each carriage 10, both inwards (in relation to the mandrel axis) and outwards.

[0046] For example, such inward adjustment is performed by at least one threaded bead 60 screwed to the carriage 10 so as to project outwardly from the closure plate 39 and inwardly from said carriage. The proximal end 60', projecting inwardly from the carriage, abuts against an abutment surface 62 made in the carriage-holder head 30. A nut 61 is screwed to the distal end 60" of the bead 60, projecting outwardly from the closure plate, to block the position of the bead at the desired stroke.

[0047] In one embodiment, adjustment of the outward carriage stroke is made by means of a stroke adjustment screw 64 screwed at a proximal end to the body of the piston 34 and passing through an aperture 65 made in the closure plate 39. A limit stop nut 66 is screwed to the distal end of said stroke adjustment screw 64, which the closure plate 39 abuts against, with the interposition of a spacer 68, when it ends its stroke. By varying the thickness of the spacer 68 the inward stroke of the carriage can therefore be adjusted.

[0048] Thanks to the presence of such mechanical blocks it is, for example, possible to repeat processing manoeuvres always ensuring the same stroke of the tool.

[0049] Moving on to the command actuators 32, in the piston 34 of each cylinder there is a first feed hole 41 coming out in the rear chamber 38 of the cylinder and a second feed hole 42 coming out in the front chamber 37 of the cylinder. Said feed holes are in fluidic communication with respective feed ducts 43, 44 made in the connection body 50; 500.

[0050] In one embodiment, a single pair of feed ducts 43, 44 contemporarily feeds the three command actuators 32. Said ducts extend in an axial direction parallel to the mandrel axis X from the connection body 50; 500 as far as a substantially central area of the carriage-holder head 30. From the end of each duct 43, 44 three respective feed holes 41, 42 extend in a radial direction.

[0051] In one embodiment variation, a plurality of feed ducts are made in the connection body, so as to individually and independently feed the command actuators of the carriages.

[0052] According to a preferred embodiment, the piston 34 of each cylinder is detachably fixed to the carriage- holder head 30, for example by screws. Advantageously, said piston 34 can be fitted to the carriage-holder head 30 in two different positions so as to change over the fluidic connection from the feed holes 41, 42 of the piston to the feed ducts 43, 44 in the connection body. Thanks to this possibility of inverting the feed holes 41, 42 of the cylinder , the same command actuator of the cylinder may alternatively cause the tool to shift from the rearward position, that is closer to the mandrel axis X, to the forward position or, vice versa, from the forward position to the rearward position. Consequently, the tool-holding device may have all the carriages performing processing from the inside to the outside of the piece (opening movement) , or all the carriages performing processing from the outside to the inside of the piece (closing movement) or performing opposite movements to each other.

[0053] The tool-holding device according to the invention can be connected to the shaft of a mandrel and fed in various ways, for example depending on the shaft of the mandrel available and/or on the basis of the available space .

[0054] In one embodiment shown in figures 1-6, the tool- holding device 1 is suitable for being fitted to a normal mandrel 200 with a hollow shaft and conical connection seat to a tool-holding device. In fact the connection body 50 is the conical shape type and has a proximal end 51 coupling, for example by screwing, to a connection tie-rod 202 to the mandrel. In this embodiment, a hydraulic distributor 220 is fitted to the rear part of the mandrel, able to place at least two external feed ducts A, B in fluidic communication ( for the delivery and the return of the command fluid) , with feed passages made in the mandrel. In particular, a first feed passage 222 is made in the connection tie-rod 202 and communicates directly with a corresponding feed duct 43 made axially in the connection body 50; a second feed passage 224 is formed by a cavity made between the connection tie-rod 202 and the mandrel body 200 and communicates with a second feed duct 44 made in the connection body 50. Given that the front part of the mandrel is fitted with a sealing ring 226 co-operating with the outer surface of said connection body 50, the command fluid which reaches the connection body is forced to enter in the second feed duct 44. In the rear surface of the carriage-holder head a groove 227 is made which a key 228 of the mandrel body 200 engages in so as to transmit the movement of the mandrel to the tool-holding device. On the opposite side, rather, a fixed part of the machine tool engages the hydraulic distributor 220, for example by means of a blocking plate 230, to prevent its rotation.

[0055] In one embodiment shown in figures 7-12, the tool- holding device 100 is suitable for being connected to any blind rotation shaft, that is to say without feed passages. In this case, the connection body 500 has a cylindrical shape and comprises a proximal end 501 coupling to any rotation shaft, so as to pick up the rotatory movement of said shaft. For example, said proximal end 501 is fitted with radial coupling tabs 501' to the shaft.

[0056] Around the connection body 500 a feed unit 503 is mounted with the interposition of roller devices 502, such as roller bearings, which can be connected to external feed ducts A, B of the command fluid and in which feed passages 505, 506 are made in fluidic communication with the feed ducts 43, 44 of the connection body.

[0057] The roller devices 502 permit the connection body 500 to rotate in relation to the feed unit 503 which is rather fixed, being intended for connection to external feed ducts.

[0058] In a further embodiment, not shown, the tool-holding device is suitable for being connected to a perforable rotation shaft, in other words in which a desired number of feed passages may be made, for example so as to independently command the carriage actuators. In this embodiment, the feed unit is fitted to the rear end of said perforated rotation shaft.

[0059] In this case, the end 501 coupling to the rotation shaft does not just act as a mechanical connection to the shaft but also as a fluidic connection between the passages made in the rotation shaft and the ducts made in the connection body.

[0060] Depending on the space available and the number of feed ducts, mixed configurations may be foreseen, that is comprising a front feed unit placed around the connection body for the connection to some feed ducts, and a rear feed unit, fitted to the rear end of a perforated rotation shaft, for connection to other feed ducts.

[0061] In practice therefore, while the embodiment with a conical connection body is specifically suitable for use on mandrels envisaging only this type of connection to a tool-holding device, the version with cylindrical connection body is suitable to be fitted to any rotation shaft, blind or perforated, with or without a conical seat .

[0062] According to a preferred embodiment, at least one further pressurisation and/or lubrication passage 45 is made in the connection body 50; 500 which can be supplied with a pressurised fluid, such as compressed air, to clean and/or lubricate the tool-holding device.

[0063] In addition, advantageously, at least one further hydraulic feed duct may be made in the connection body 50; 500 and /or in the carriage-holder head 30 to command at least one hydraulic motorised tool fitted to a respective tool attachment group fixed on a carriage.

[0064] To summarise, the tool-holding device according to the invention is provided with one or, preferably, several tool-holder carriages which may operate individually or in a combined manner.

[0065] In particular, it is possible to set, independently for each carriage, the direction of translation in relation to the mandrel axis, that is to close or open, the starting position of the tool in relation to said axis and the distance of the tool from the front surface of the tool-holding device. In other words, it is possible to set the position of each tool both in a radial and axial direction, depending on the type of processing to be performed.

[0066] Such flexibility of configuration of the device makes it possible, by fitting the appropriate tools, to perform innumerable types of processing of the piece. For example, processing can be performed in undercut, truncation, frontal processing, threadings . In addition, advantageously, the same tool-holding device can be used as a gripping tool of the pieces. Examples of tools which can be advantageously fitted to the device according to the invention are: deformation, rolling, truncation rollers, threading and turning tools. Later in the description, some examples of tools and the relative processing which can be performed with the tool-holding device according to the invention will be described.

[0067] Thanks to the contemporary use of several tools which can move contemporarily, such processing may be performed in a much shorter time than at present.

[0068] For example, various contemporary types of processing may be axially or radially incrementally combined, that is to say with the tools positioned radially or axially in an incremental manner in relation to each other. For example, a first tool may perform a roughing , a second tool a processing and a third tool a finishing .

[0069] For example, an inner or outer thread may be made on a piece much faster than at present. In fact using a traditional die the threading is performed and then the tool must return back over the thread just made. With the tool-holding device according to the invention, rather, one or more combined tools make the threading; when completed, the carriages shift radially and the tool- holding device can be returned in a very short time.

[0070] Thanks to the fact that the thrust of the command actuators is coaxial to the respective carriages, thereby avoiding transfer means between the movement of the actuator and that of the carriage, adjustment and drag wear are eliminated.

[0071] Advantageously, the force exerted by the command actuators can be summed, multiplying by the number of actuators used, compared to the force exerted by a single actuator; in an equivalent manner, for the same applied force a significantly lower working pressure may be used.

[0072] Advantageously, in the case of several carriages, the radial load components tend to cancel each other out and the mandrel therefore works in reduced or nil stress conditions.

[0073] The carriages angularly equally distanced from each other, that is positioned in a stellar configuration on the same plane, make it possible to support the piece to be processed without it flexing. In other words, no load components which tend to move the piece in the gripping body are created. A natural balance is rather created which is maintained even when the number of carriages is increased,

[0074] In addition, the pressurised fluid on the surface of the actuator cylinders has the advantageous effect of damping the vibrational effect of the device.

[0075] The device can be fitted to mandrels with hollow shafts or mandrels with blind shafts, with or without a conical seat.

[0076] In addition, the control of the carriages can be performed by setting the actuation times, rather than by means of limit stops: this permits fast and simple fitting of the device to all units without the need to redesign the electronic control.

[0077] Despite its versatility and flexibility of use, in particular thanks to the fact that the sleeve of the actuation cylinder constitutes the carriage itself, the device has reduced axial dimensions and is easy maintenance .

[0078] Some examples of processing which can be performed using the tool-holding device according to the invention will now be described.

[0079] In figures 14-24 one of the tool-holder carriages 10 of a tool-holding device 1; 100 is shown in cross- section. The carriage 10 bears a tool-holder group 300 to which a relative processing tool is fitted. In addition, the figures schematically represent any further processing tools fitted on the relative carriages, not shown, and the end of a piece 400 to be processed or processed.

[0080] Figure 14 shows the axial profiling of a piece 400. Three tools are used 301, 302, 303 for example having different cutting profiles from each other, axially staggered so as to form a single profile as resulting from the sum of the individual profiles. The contemporary use of three tools thereby permits a profile to be made having an extension equal to the sum of the profiles of the individual tools in a third of the time which would be required with a single tool, as happens traditionally.

[0081] Figure 15 shows the front profiling of a piece. In this case, the three carriages 10 are radially staggered. It should be noted that, if n is the number of carriages and therefore of tools, and m is the number of cutting edges of each tool, the processing time is reduced n x m times.

[0082] Figure 16 shows the truncation processing of a tube 400. Such operation can be performed with a roller tool 301, fitted idle to the tool-holder group 300. The carriage which the tool is fitted to is pushed radially inwards so as to achieve the desired pressure of the tool on the tube. Alternatively a first cutting tool 302 may be used and subsequently a second tool 303, fitted on a second carriage, for the splicing and external chamfering of the truncated tube.

[0083] Figure 17 shows a threading processing of a piece 400 by rolling. In this case too, the tool 301 is a roller fitted idle to the relative tool-holder group 300 and having a profile corresponding to the thread to be made on the piece.

[0084] Figure 18 shows a thread of a piece 40 achieved with a plurality of utensils 301 (only one of which is shown) , each fitted to a respective carriage 10. The tools are axially staggered. At the beginning of the work cycle, the carriages move radially so as to engage the outer or inner surface of the piece. The mandrel is then actuated to perform the threading. With the same pitch a number of threads equal to the number of tools can be made contemporarily. At the end of the processing the tools are radially distanced from the surface of the piece so the processing unit can therefore be drawn back very rapidly. It should be noted that, providing the individual tools with a compensation system, such as a spring, n threads can also be obtained with different pitches to each other.

[0085] Vice versa if the fixed tools are used to process the piece to be threaded, once at the desired depth the mobile tools can be used, which being in rotation, automatically make a thread channel. By co-ordinating the return of the unit the threading can be performed, with a consequent saving of time and number of units needs for the processing.

[0086] In other words, such variation envisages that the aforesaid tool-holding device comprises at least one fixed tool, which when the mandrel is actuated, performs a threading at the desired depth on the piece. After such fixed tool has reached the desired depth, one or more carriages are radially drawn up to the surface to be threaded to make a thread channel. This way, when the mandrel is commanded to return to disengage the tool- holding device from the piece, the shavings generated by the threading are advantageously extracted from the cavity defined by the thread. Consequently, such shavings do not remain in the cavity of the thread but are, on the contrary, moved by the tool towards the relative mouth, advantageously leaving a cavity free of shavings.

[0087] Figure 19 shows the threading of a piece 400, where the threading is of a depth such as to render the removal of shavings by a tool in a single passage impossible. Currently therefore, several work cycles are performed to achieve the desired thread. The tool-holding device according to the invention rather makes it possible to perform the following innovative processing method, known as "incremental" threading.

[0088] n tools 301-303 are used contemporarily, each fitted to a respective tool-holder group attached to a respective carriage. The carriages are radially mobile in relation to the piece to be threaded. The carriages are angularly distanced from each other by an angle of 360°/n. P being used to indicate the pitch of the thread, the carriages are, moreover, axially staggered from each other by a height of P/n.

[0089] A first carriage 10 is radially drawn up to the surface to be threaded and the mandrel is commanded so that the relative first tool 301 performs a threading having a depth equal to the cutting edge of the tool, less than the desired depth. A second tool 302, axially staggered from the first by a height equal to P/N, is radially drawn up to the piece to be processed with a greater stroke than the radial stroke of the first carriage, so as to remove further shavings. Any further tools 303, axially staggered in relation to one another by a height equal to P/n, are drawn up to the piece to be processed in sequence, with a progressive increase of the radial stroke. In other words, the total cross-section of shavings to be removed is divided into partial cross- sections removed by the respective tools, but in a single passage, that is to say, contemporarily (once all the tools have started to work) . Such a processing unit may therefore be defined a threader or incremental die with n contemporary passages. It is to be noted that the work cycle is further shortened by the fact that, at the end of the processing, the tools do not move back over the threading made to return to the starting position but are radially distanced from the processed piece so as to permit a rapid return of the unit. [0090] Figure 20 shows the rolling of a piece 400 to reduce the roughness of the inner and/or outer surface. An idler roller 301, radially mobile in relation to the piece to be processed as far as a position in which the desired pressure on the surface to be rolled is achieved, is fitted to at least one carriage 10.

[0091] Figure 21 shows the rolling process for deforming the end 401 of a tubular element 400. An idler roller 301, having a conical lateral surface 301' ending at the base with a curved section 301", corresponding to the desired deformation of the end of the piece, is fitted to at least one carriage 10. The tool is radially mobile in relation to the piece to be processed as far as a position permitting the desired pressure on the rim to be deformed to be achieved. Advantageously, the deformation occurs by rolling contact thereby preventing seizing phenomena. For such reason, such deformation may be defined "cold".

[0092] Figure 22 shows the processing for obtaining one or more polygonal surfaces 402 on a cylindrical piece 400. A motorized tool 310 fitted with at least one cutting edge 311 is fitted to a tool-holder group 300. Note the feeds A, B, for example coming out of the tool-holder head 30, dedicated to feeding the motorised tool 310. By combining the number N of revs performed by the tool-holding device around the piece to be processed, which is kept still, with the number n of revs of the tool, a flat surface is obtained with a cutting edge, the depth of which in relation to the piece, is given by the radial position of the tool. As the number Z of cutting edges of a tool varies, different polygons can be obtained. With several carriages, each fitted with a motorised tool, a plurality of polygons can be obtained contemporarily.

[0093] Figure 23 shows a processing for radial helical channels on the outer (or inner) surface of a piece 400. In this case too at least one motorised tool 310 is used bearing a bur 312 rotating around a bur axis perpendicular to the surface of the piece to be processed. The tool-holder carriage is radially mobile to perform a shift P. By co-ordinating the number of revs N of the tool-holding device with the axial translation T of said device, with the number of revs n of the bur and with the shift P of the carriage , it is possible to make a helical channel on the surface of the piece. If the shift P of the carriage is controllable, for example by a proportional valve, a helical channel of varying depth may be obtained.

[0094] Figure 24 shows a processing to obtain axial spiral channels on the front surface of a piece 400. In this case too at least one motorised tool 310 is used bearing a bur 312 rotating around a bur axis perpendicular to the front surface of the piece to be processed. The tool- holder carriage is radially mobile to perform a shift P controlled for example by a proportional valve. By co- ordinating the number of revs N of the tool-holding device with the axial translation T of said device, with the number of revs n of the bur and with the shift P of the carriage , it is possible to make a front channel in the shape of a spiral. The axial shift T of the tool- holding device determines the depth of the channel.

[0095] Lastly, the same tool-holding device may be used, providing it with appropriate gripping organs, as a gripping tool, both rotating and static, to be fitted for example to the mandrel of a robot.

[0096] It is clear that the types of processing described above may be freely expanded and combined with each other. The only condition to be satisfied is that separate, independently controllable hydraulic feeds should be available.

[0097] The embodiments of the tool-holding device illustrated in figures 25 and 26 differ from the previous only by the fact that at least one base 70 is fixed to the lateral surface of the carriage-holder head 30 for the attachment of a support group of a fixed tool, that is to say not radially mobile as in the case of the mobile carriage 10. Preferably, several bases 70 are fixed to the head 30, for example alternately with the tool-holder carriages 10.

[0098] In figure 26 the attachment groups 300 of a tool 301, each supported by a respective mobile carriage 10, can also be seen.

[0099] The possibility of combining fixed tools and mobile tools on a single carriage-holder head makes it possible to greatly reduce processing times. For example, a tool- holding device with mobile carriage and two fixed tools enables a ring or spacer to be obtained in a single cycle. When the fixed internal and external tools have turned the inside and outside the mobile tool cuts in, truncating the piece to size with relative external chamfers. The piece is thereby obtained in a single cycle, avoiding at least two tool changes which add both to the changeover time and processing time.

[00100] Figures 27 and 28 show a tool-holding device fitted with a mechanical synchronisation system 80 of the radial movement of the carriages 10. Said synchronisation system 80 comprises a synchronisation disc 82, fitted idle to the connection group 50, behind the carriage- holder head 30. For example, said synchronisation disc is inserted in a cylindrical body 83 which connects to the carriage-holder head 30. Said synchronisation disc 82 bears a plurality of levers 84, one for each mobile carriage 10. In particular, each lever 84 has a fixed pin 86 constrained to the disc 82 and a mobile pin 88 engaging in the outer sleeve 36 of each command actuator 32, in other words in the body of each mobile carriage 10. Said mobile pin 88 passes through a slot 90 made in the rear wall of the carriage-holder head 30.

[00101] Consequently, if one mobile carriage 10 starts to move before the others, for example on account of different friction, such carriage 10 drags the mobile pin 88 radially. The translation of said mobile pin 88 causes a rotation of the synchronisation disc 82, which in turn causes the translation of the mobile pins 88 of the other levers 84, and therefore the movement of the other mobile carriages 10.

[00102] In figures 29 and 30 three levers 84 can be seen initially in a closed position ( figure 29) , that is defining a circumference around the rotation axis of the tool-holding device, determined by the rearward position of the carriages, and then the shifting of the levers in an open position (figure 30) corresponding to the advancement of the carriages 10.

[00103] In the embodiment variation shown in figure 31, the cylindrical body 83 has a rear extension which defines a seat 92 for a sealing element (not shown) . Said cylindrical body 83 may therefore be coupled to a pressurisation or lubrication system of the carriage- holder head 30.

[00104] The synchronisation system 80 described above proves particularly useful, combined with the possibility of adjusting the stroke of the carriages 10, when said carriages 10 bear gripping jaws to form a gripping or blocking group of a piece. In fact, with such synchronisation system it is possible to ensure the perfect centring of the piece to be blocked.

[00105] A person skilled in the art may make modifications, adaptations and substitutions of elements with others functionally equivalent to the embodiments of the tool-holding device according to the invention so as to satisfy contingent requirements, while remaining within the sphere of protection of the following claims. Each of the characteristics described as belonging to a possible embodiment may be realised independently of other embodiments described.