DESCRIPTION

The present invention relates to a part-guiding device for machines for rolling hollow bodies, a machine for rolling hollow bodies provided with such a device and a method for performing rolling by means of said machine.

It is known in the technical sector relating to the machining of shaped parts that there exists the need to perform machining of said parts by means of cold-deformation methods.

These methods include rotary planetary thread rolling which involves moving the parts between a fixed tool (annular segment) and a rotating deformation tool (roller) which rotates about its axis of rotation and moves the part about its axis and along a predefined circumferential trajectory depending on the configuration of the part to be rolled. One or both the tools have superficial structures (grooves/threads), the features (rolling profile) of which cause a planned displacement of material from one side to another of the part, whereby modifications in the perimetral dimensions of the part occur.

These types of machining operations include in particular the rolling of pins on which a threading on the outer surface is formed or the perimetral dimensions (diameter) of which are varied in order to produce a blank on which a second rolling operation forms the thread, a particular type of such machining operation consisting in the rolling of hollow pins.

For these specific products it is in fact necessary to provide opposition means which must be inserted inside the cavity in order to prevent the part from becoming deformed during rolling owing to the radial forces which are applied in order to obtain the displacement of the material from one zone to another of the said part.

An example of such a machining operation consists in the formation of threaded hollow inserts, which are widely used for example in the furnishing sector for the assembly of component parts of furniture of various kinds.

SU 1669625 also discloses a rolling machine for hollow bodies which comprises a part-guiding pin which is displaceable from a position extracted from the hollow body into a position inserted inside the hollow body and integral with a drum rotating in phase with the roller acting on the external surface of the hollow body within the rolling sector.

Rotary machines of this type have a fundamental drawback arising from the fact that the rotating drum and therefore the rolling roller rotate at a constant speed, while the hollow body, which moves in contact with a fixed opposition guide (segment), has a variable speed of rotation around the axis of the drum owing to the variation in diameter caused by the displacement of the material; this difference between the speeds is therefore the cause, during rolling, of phase shifiting between the drum carrying the pin and the part (hollow body) being rolled, with consequent deformation (ovalization) of the part, resulting in it being discarded.

The technical problem which is posed therefore is that of providing a rotary machine for rolling hollow bodies (or devices for use in such a machine) which is able to provide a solution to the problems of the prior art and in particular prevent deformations of the hollow body during rolling.

In connection with this problem it is required in particular that the machine or the associated devices should be easy to manufacture, have small dimensions and be able to be easily installed.

These results are obtained according to the present invention by a partguiding device with phase recovery for machines for rolling hollow bodies according to the characteristics features of Claim 1 ; by a machine for rolling hollow bodies, provided with a such a device according to the characteristic features of Claim 12, and by a method for rolling hollow bodies according to the features of Claim 20.

Further details may be obtained from the following description of a nonlimiting example of embodiment of the subject of the present invention provided with reference to the attached drawings in which:

Figure 1: shows a perspective view from above of a rolling machine according to the present invention;

Figure 2: shows a perspective side view of the machine according to Fig.1 ;

Figure 3a: shows an exploded view of the part-guiding assembly with synchronization recovery according to the present invention;

Figure 3b: shows a perspective front view of the part-guiding device with synchronization recovery according to Fig. 3a;

Figure 4: shows a front view of the device according to Fig. 3;

Figure 5: shows a perspective view of the carousel for transporting the assembled part-guiding device; Figure 6: shows a top plan view of the carousel according to Fig. 5 with an indication of the working sectors and the corresponding speeds of the rotating parts;

Figure 7: shows a cross-sectional view along the plane indicated by V-V in Fig. 4, with the synchronizing body and the part-guiding pin in a predefined start-of-cycle position and in a synchronizing position following the passage of the part into the rolling sector.

As shown in Figs. 1 , 2 and assuming solely for the sake of easier description and without a limiting meaning a set of three reference axes, i.e. in a longitudinal direction X-X corresponding to the direction of entry of a hollow part 1 into the machine, transverse direction Y-Y corresponding to the widthwise dimensions of the machine, and vertical direction Z-Z corresponding to the heightwise direction of the machine, for the sake of simplicity assumed as coinciding with the axis of rotation of a rotating carousel described below, an example of embodiment of a rolling machine for rolling hollow bodies according to the invention comprises a frame 10 comprising a lower surface 11 along a plane X-Y, an upper surface 12 along a plane X-Y supporting the devices 20 for actuating the rotating parts of the machine and a set of devices 1000 for handling the part to be rolled.

The handling devices 1000 comprise in particular:

- a carousel 400 rotating about the vertical central axis Z-Z, carrying at least one part-guiding device 2000;

- rolling means 300 for rolling the hollow part 1, which define a part rolling sector;

- feeding means 100 for feeding the hollow parts 1 to be rolled, preferably extending in a longitudinal/radial direction X-X and designed to feed correctly oriented hollow parts 1 in an insertion sector located in the vicinity and upstream of the rolling means 300 and of the rolling sector;

- guiding means 200 for guiding and feeding the parts 1 inside the insertion sector, configured to cause synchronized feeding of each part with a respective part-guiding device 2000 so as to allow the coaxial coupling between the part 1 and the part-guiding device and so as to cause the subsequent insertion of the hollow part 1 inside the rolling sector.

Preferably, said feeding means 100 comprise a guide 100 inclined towards the axis of rotation of the carousel and designed to contain and keep correctly oriented the hollow parts 1 which are displaceably moved, for example by means of gravity, towards one end 110a of the guide arranged in the insertion sector in the vicinity and upstream of the rolling means 300 which define the sector for rolling the part; the displacement of the parts 1 may also be performed, for example, by a rotating belt. The feeding means are conventional per se and do not require further detailed description.

Advantageously, the guiding means 200 for guiding and synchronized feeding of the parts 1 inside the insertion sector may comprise a curved pusher 201 oriented tangentially and designed to push the rotating part 1 around the vertical central axis Z-Z, in particular upon operation of a hinged arm 202 actuated by a cam 203 in turn rotated by means of a bevel gear 203b connected to the shaft of a main motor 203a located on the lower surface 11.

The curved pusher 201 may preferably cooperate with guiding means, such as a curved tongue 204, arranged in the insertion sector between the point of entry of the part and the start of the rolling sector s300.

The rolling means 300 for rolling the hollow part 1 comprise in particular:

-- a first, fixed, tool 301 with an annular development, in particular in the form of an annular segment, with an inner (concave) surface directed towards the axis of rotation Z-Z and shaped with a suitable rolling profile; the fixed tool 301 is arranged in an external position in the radial direction Y-Y with respect to the vertical axis of rotation Z-Z;

- a second, rotating tool 302 (or roller), generally cylindrical, with an outer side surface parallel and directed towards the inner surface of the first, curved, fixed tool 301 and shaped with a rolling profile compatible with that of the fixed tool for the formation of the desired deformation of the hollow part by means of rolling. The rotating tool 302 is concentrically arranged in a radially more inner position relative to the first fixed tool 301 and is movable rotationally about the central vertical axis Z-Z, upon command of an associated actuating device 303, to which it is connected and which is arranged on the lower surface 11.

The rotational operation of the carousel 400, guiding and advancing means 200 and/or rolling roller 301 may be suitably coordinated by means of connection means, which in the example shown are of the mechanical type comprising kinematic chains, but which could also be of the electronic type, or a combination of mechanical and electronic means.

The rotating carousel 400 carries one or more part-guiding assemblies 2000, each comprising:

-- coupling means 2410 suitable for engagement with the internal cavity 1a of the hollow part 1 and

-- means 2500 for phase-synchronizing the relative movements of the part 1 undergoing rolling and the carousel 400.

The coupling means 2410 comprise a pin 2410a oriented parallel to the vertical direction Z-Z, with a form substantially corresponding to that of the internal cavity 1a of the part 1 to be formed and with external dimensions slightly smaller than those of the said cavity, so as to be able to be inserted/exit without play into/from the said cavity; by way of example, the cavity and the pin may be circular with dimensions defined by the respective internal and external diameter.

The pin 2410a is movable relative to the carousel 400 in the vertical direction from a raised position, extracted from the cavity of the part 1, into a lowered position, for insertion into the said cavity.

Advantageously, the movement in both senses of the vertical direction is provided by an actuating assembly 2510 (Figs. 3,4) comprising a tappet system 2508 movable on a cam 2509 rotationally fixed with respect to the carousel 400.

Vertical-axis springs 2506 may be arranged between the part-guiding assembly 2000 and the carousel so as to push the part-guiding assembly 2000 and therefore the pin towards the position lowered in the vertical direction, in combination with the interaction between cam 2509 and tappet system.

It is understood that the vertical-direction actuating assembly could also be different.

In greater detail, the part-guiding assembly 2000 comprises a vertical slider 2501 , movable on a corresponding guide 2501a of the carousel 400 so as to form coupling means for coupling the part-guiding assembly 200 with the carousel 400, which make the part-guiding assembly 2000 rotationally integral with the carousel 400, but allow the vertical displacement of the partguiding assembly 2000 and therefore the pin 2410a for engagement with the part 1.

The slider 2501 has, fastened thereto, a plate 2502 which carries:

- an upper support 2503 in the form of an annular segment which has, mounted on its bottom surface, an upper guide 2503a with a corresponding curved form for guiding the circumferential rotational movement of a body 2521 of the synchronizing means 2500 described below; the two verticalaxis springs 2506 are also arranged on the upper support;

- a lower support 2504 in the form of an annular segment which has, mounted on its bottom surface, a lower guide 2504a with a corresponding curved form for guiding the rotational movement of the phase-synchronizing body 2521.

The pin 241a is supported by a bracket 2411 fixed to said body 2521 of the phase-synchronizing means 2500 together with which it rotates during rolling of the part.

The position of the pin 2410 with respect to the body 2521 in the radial direction is preferably adjustable so as to be able to move the pin into a position coaxial with the cavity 1a of the part 1 to be rolled, inside which it must be inserted. Preferably, the flange 2411 comprises for this purpose one or more radial centring slots inside which suitable fastening means for fixing to the body 2521 are inserted.

The phase synchronizing means 2500 therefore comprise the body 2521 rigidly joined to the bracket 2411 which supports the pin and to an upper slider 2523 and to a lower slider 2524 which are respectively slidable circumferentially on a corresponding upper curved guide 2503a and lower curved guide 2504a of the part-guiding assembly 2000.

The pin-carrying body 2521 has, associated with it, a mechanism 2525 comprising a rod 2526 which extends in a substantially tangential direction and one end 2526b of which is connected to the plate 2502 for coupling with the carousel by means of a flange 2527, preferably via a vertical-axis articulation 2526c, and the opposite end 2526 of which has a stop surface for a spring 2528 which is normally extended and is coaxially mounted on the rod 2526.

The rod 2526 passes through the first body 2521 of the part-holder assembly 2500 and the spring reacts on one side against the end stop of the rod 2526a and on the other side against an element 2521 rotationally integral with the body 2521. In the example shown (Fig. 3), this element is a vertical cylinder 2521a stably inserted inside a cavity of the body 2521 and designed to slide on the rod 2526 when the body 2521 rotates relative to the plate 2502. It is clear that other solutions are possible and, for example, this element could also be a vertical surface of the first body 2521 against which the spring acts.

As shown in Figs. 6 and 7, during the rotational movement of the carousel 400 and of the part-guiding assembly 2000 in the rolling sector s300 at a speed W3 and direction r+ (conventionally assumed as being clockwise), the body 2521 and the pin 2410a perform a phase-synchronizing rotation relative to plate 2502 in the opposite direction r-, compressing the spring 2528 and continuously recovering the difference in motion due to the variation (for example increase) of the diameter of the part 1 carried by the pin 2410a.

Figure 7 shows in broken lines an example of a retracted phasesynchronizing position of the body 252 T and the pin 2410' at the end of the rolling step, with the spring 2528' compressed.

Therefore, the pin 2410a rotationally integral with the body 2521 is coupled to the plate 2502 and therefore to the carousel 400 with a degree of freedom which allows rotation thereof with respect to the plate (and therefore the carousel 400) about the vertical central axis Z-Z of rotation of the said carousel and in the opposite direction to the direction of rotation of the carousel, against the action of the resilient means 2528 which, normally extended, are compressed by said rotation of the body 2521 and pin 2410a during rolling of the part in the rolling sector, thus acting as phasesynchronizing means which continuously rephase the relative movements of the pin 2410a and carousel 400.

During the phase-synchronizing rotation of the body 2521, the vertical-axis articulation 2526c may advantageously allow rotation of the rod 2526 about a vertical axis such as to maintain the relative orientation of the rod 2526 and the body 2521 which ensures optimum displacement of the body 2521 on the rod 2526 itself.

Preferably, the flange 2527 is crossed by screws 2527a extending transversely with respect to the flange and acting on the body 2521 so as to adjust the positioning thereof in a predefined start-of-cycle position for the movement of the body 2521 on the upper guide 2503a and lower guide 2504a, preferably in a central position with respect to the guides.

In this way, at the end of the rolling operation, the pin 2410a, pushed by the decompression of the spring 2528, will return into the predefined start-of- cycle position, for example in a return sector s400 (Fig. 6), before the start of a new machining cycle. The machine may also comprise an expulsion unit 600 for expelling from the machine the rolled part 1, within an extraction sector s600 in which the vertical extraction of the pin 2410a from the part 1 and the extraction of the part 1 from the machine is performed; the unit is conventional per se and not described in detail.

With this configuration, operation of the part-guiding device 2000 and the rolling machine is as follows:

- feeding of the hollow parts 1 to the zone for entry into the insertion sector s200 by means of the feeding means 100;

- rotationally operating, about the vertical axis Z-Z, the carousel 400 carrying the part-guiding devices 2000, at a speed W3; and

- correspondingly, the pin 2410a rotates at the same speed W3;

- operating the guiding and advancing means 200 which move the part 1 rotationally about the axis Z-Z in the insertion sector s200 towards the rolling sector s300;

- rotationally operating the rotating rolling tool (roller) 302; preferably, the carousel 400, the advancing means 201 and/or the roller 302 are operated by an ordinary motor 203 and therefore simultaneously;

- synchronized rotation of the carousel 400 and the hollow part 1, which brings the pin 2410a into a position coaxial with the cavity 1a of the part 1;

- continuing with its rotation, the carousel brings the part-guiding assembly 2000 into a circumferential position such as to cause the reaction of the tappet system 2508 against the profile section of the cam 2509, thus freeing the part-holder assembly 2000 which is lowered in the vertical direction Z-Z by the pushing action of the springs 2506 so as to insert the pin 2410a into the cavity 1 a of the part;

- entry into the rolling sector s300 of the part 1 with pin 2410a inserted, between the rotating tool 302 and the fixed tool 301;

- rotation of the rolling tool 302 which, coming into contact with the part, causes by means of friction: both the rotation about its vertical axis and the circumferential advancing movement (revolution) of the part within the rolling sector about the vertical central axis Z-Z;

- the shape of the profile of the rolling tools 301 ,302 and the combined rotational and revolving movement of the part 1 within the rolling sector s300 cause the desired displacement of the material along the part;

- during the advancing movement of the part in the rolling sector s300 the part 1 changes its dimensions owing to the displacement of material along its vertical axis of rotation, causing a variation in the speed of circumferential advancing movement of the part (in particular of the axis of the part 1) within the rolling sector; this therefore results in phase desynchronization with the constant speed of rotation W3 of the carousel 400, said difference being potentially the cause of deformations such as ovalization of the part 1 being rolled;

- intervention of the means 2550 for phase-synchronizing the part-holder device 2000 so that, following for example the lag (of the axis) of the part 1 along the rolling trajectory, the entire body 2521 moves on the guides 2503,2504a in the direction r- opposite to the direction r+ of rotation of the carousel (Fig. 7), compressing the spring 2528 and causing circumferential retraction of the pin 2410a which thus results in continuous rephasing of the advancing and rotational movements of the part 1, inside the rolling sector s300, with the speed of rotation of the carousel and thus avoiding modifications in the form of the part and therefore correct rolling thereof;

- once rolling has been completed, the part reaches the extraction means 600 where the pin 2410a is extracted from the cavity 1a and part 1 is pushed out of the machine for recovery thereof.

The spring 2528 is decompressed in the expulsion sector s600 or return sector s400, bringing the pin 2410a back into the predefined start-of-cycle position, which is adjusted by the adjustment screws 2527a.

In order to obtain correct synchronization of the relative movements it is envisaged in particular that:

- the speed of rotation W3 of the carousel 400 about its axis Z-Z is constant for the entire rolling cycle;

- the speed of circumferential advancing movement W1 (of the axis) of the part 1:

- is constant and equal to W3 in the sector s200 for insertion and sector s600 for expulsion of the part into/from the rolling sector, in particular at least along the sections for insertion/exit of the pin into/from the hollow part 1;

- is variable within the rolling sector owing to the variations in diameter of the part following the displacement of material and corresponds to W3, apart from the synchronizing actions by the spring 2528 which, being compressed, allows the body 2521 to slide on the guides, recovering the lag of the part 1 ;

- the speed W2 of rotation of the pin around the axis Z-Z: — corresponds to W3 in the sectors for insertion/expulsion of the part so as to allow insertion/removal of the pin;

— corresponds to the speed W1 of advancing movement of the part in the rolling sector, being correspondingly varied by the action of the synchronizing means;

-- the speed W4 of the rotating rolling tool 302 is for example twice the speed W3 of the carousel.

It is therefore clear how the part-guiding device 2000 with synchronization recovery is able to compensate for the desynchronization which occurs in the rolling sector between the advancement of the part to be rolled with the pin inserted inside the cavity of the part and the rotation of the carousel about its axis, thereby avoiding damage to the part, such as ovalization and breakages, during rolling.

This thereby ensures safe machining of a hollow part where material must be displaced so as to create thicknesses suitable for the formation of a threading, this being generally performed during subsequent steps and in other dedicated machines.

Although described in connection with a number of embodiments and a number of preferred examples of implementation of the invention, it is understood that the scope of protection of the present patent is determined solely by the claims below.