Machine for bending an elongated workpiece without wrinkling

A machine for bending an elongated workpiece without wrinkling has a roller-like bending die (2) with a vice (3) adapted to retain one end of the elongated workpiece (P) to be bent. The roller-like bending die (2), being provided with a central hole (5) and a groove profile (6) and rotatable about a rotation axis (y), bears, centrally and coaxially in its groove profile (6), a plate element (18) oscillating with respect to the bending die (2) around a rotation axis (y) thereof. The plate element (18) having a peripheral edge (19) which continues the groove profile (6) of the bending die (2) consists of at least two pieces (20, 21) which are adapted to be connected to one another to surround the bending die (2).

TECHNICAL FIELD

The present invention relates to a machine for bending an elongated workpiece without wrinkling.

BACKGROUND ART

Normally, the formation of wrinkles in the tubular wall of an elongated piece, subjected to high pressure stresses in a bending operation, is avoided by means of an anti-wrinkle tool positioned near the bending die. The anti-wrinkle tool works as long as it is positioned correctly with respect to the bending die. The presence of a non-uniformity or even small gap between the bending die and the anti-wrinkle tool is sufficient to create wrinkles, thus worsening the quality of the elongated workpiece after bending. The anti-wrinkle tool is also constructed so that it can be modified to take into account wear during use. Furthermore, the anti-wrinkle tool must be completely replaced when worn due to having been subjected to a certain number of bending operations.

In order to remedy to these drawbacks, US 2008/0110223 describes a machine for bending an elongated workpiece without wrinkling. The machine comprises a roller-shaped die provided with a circumferential groove, and a vice adapted to hold an end of the elongated workpiece to be bent. The die is rotatable around a rotation axis, bearing, centrally and coaxially in its groove profile, a plate-like element oscillating on bearings with respect to the die around the rotation axis thereof. To receive this oscillating plate-like element, the die is made in two parts. The oscillating plate-like element has a circumferential profile shaped to match the contour of the elongated workpiece to be bent. US 2008/0110223 states that, thanks to this oscillating plate-like element, a reduction of the non-uniformity and of the air gaps is obtained in those circumferential regions of the elongated workpiece to be bent which are at higher risk. The structure constituted by the anti-wrinkle tool and the oscillating plate-like element is exposed to a minimum wear due to friction and therefore has a prolonged service life. The oscillating plate-like element is able to guide the elongated workpiece during the bending operation and to reduce to a minimum the stretching stresses of the tubular wall of the elongated workpiece.

Therefore, the oscillating plate-like element can be considered as a single piece anti-wrinkle tool. To be coupled to the bending die, the structure of the bending die is in two parts with consequent manufacturing disadvantages.

JP 2017 094374 A describes a unit of two-piece pipe bending die and anti-wrinkle tool in several parts that partially surround a die bushing. The die bushing joins the two pieces of the pipe bending die by an axial element to provide an axis of rotation. US 2016/175909 A1 describes a unit of two-piece pipe bending die and anti-wrinkle tool in several parts, of which only a first part is inserted inside the pipe bending die that is split laterally to allow this insertion. At least a second part of the anti-wrinkle tool is removably connected to the first part to allow a replacement of the second part when it is worn.

JP 2017 087220 A discloses a unit of laterally split pipe bending die and anti-wrinkle tool in several parts, of which only a first part is inserted inside a split die and is retained there by a bushing and an axial shaft element. At least a second part of the anti-wrinkle tool is removably connected to the first part of the anti-wrinkle tool to allow a replacement of the second part when it is worn.

All the units of bending die and anti-wrinkle tool of the above cited prior art require that the die either be partially split transversely or be made in two parts to allow the anti-wrinkle tool to be mounted. This requires a bushing that is held by a die shaft and surrounded by one or more parts of the anti-wrinkle tool. Furthermore, the dies described in the aforementioned documents imply, for mounting the anti-wrinkle tool in the split die, a disassembly of the die shaft and the bushing.

Furthermore, the anti-wrinkle tool is not configured symmetrically so as to be mounted on the bending die in bending an elongated workpiece in the right direction and, after disassembled and inverted, in bending in the left direction the elongated workpiece.

SUMMARY OF THE INVENTION

The present invention aims to overcome the aforementioned drawbacks.

A main object of the present invention is to allow a bend without the formation of wrinkles of an elongated workpiece, with a bending die having a structure made in one piece and without diametral splits even if only partial.

Another object of the invention is to provide an anti-wrinkle tool which can be mounted on a die without disassembling the die shaft.

Yet another object of the invention is to provide a die with an anti-wrinkle tool which allows a bending of a piece both to the right and to the left direction.

To achieve the aforementioned purposes, the present invention, as defined in claim1attached to the present description, provides a machine for bending an elongated piece without wrinkling comprising a bending die that has a roller-shaped structure provided with a central hole and a groove profile, the bending die, rotatable about a die rotation axis, bearing centrally and coaxially in its groove profile, a plate element oscillating about the die rotation axis, and eccentrically a vice adapted to retain one end of the elongated workpiece to be bent, the plate element having a peripheral edge which continues the groove profile of the bending die, wherein the roller-shaped structure of the bending die is in a single piece, and the plate element consists of at least two pieces which are adapted to be connected to one another after surrounding the roller-shaped structure of the bending die.

The plate element has a longitudinally symmetrical shape and is adapted to be mounted in the bending die in bending in the right direction an elongated workpiece, and to be disassembled and mounted again upside down in the bending die in bending in the left direction the elongated workpiece.

The vice has a plane of symmetry for being adapted to be mounted in the bending die for bending in the right direction the elongated workpiece, and to be disassembled and mounted again in the bending die after being rotated by 180°, for bending in the left direction the elongated workpiece.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

Reference is firstly made toFIGS.1to3which are a three-quarter perspective view from above of the machine according to the invention, in beginning the bending of an elongated workpiece, an end view opposite to the bending die and a top view of the machine inFIG.1.

The machine according to the invention comprises a body1, a bending die2, a vice3designed to hold an end of an elongated workpiece P, and a counter die4.

As shown in detail inFIG.4, which is an exploded perspective view of the bending die2and of the vice3, the bending die2has a single piece roller structure, which is provided with a central hole5and a circumferential groove profile6, rotatable about a die rotation axis y. The bending die2has, on both its sides (in the figures only the upper side is shown), a die boss7which surrounds the central hole5of the bending die2. Furthermore, the bending die structure is lightened by a missing portion that is shaped like a circular segment, that is, the bending die2is cut according to a plane α parallel to the die rotation axis y and passing through a chord c of the circular segment. The plane α is indicated with its trace inFIG.3. The circular segment has a diametral symmetry axis x, as shown inFIG.4. Two egg-shaped support plates8,8are mounted on both sides of the bending die: they have a large hole9coaxial to the die rotation axis y so that each support plate8surrounds a respective die boss7; moreover, each support plate8has a small hole10overlying said missing portion shaped as a circular segment and being centered in an axis y1parallel to the die rotation axis y.

Each support plate8has an anti-rotation projection11in an indentation12of the bending die2.

A bushing13is arranged between the two egg-shaped support plates8,8and held therein by a fulcrum pin15passing through a bushing hole14. The fulcrum pin15also passes through the small hole10of each of the two egg-shaped support plates8,8and has a perforated head16for connection to the vice3, as will be seen below.

The bending die2has, in its groove profile6, centrally and coaxially in the profile of the same, a channel indicated with17inFIG.4. The channel17serves to contain a plate element18which, thanks to the fact of being free in the channel17, oscillates with respect to the die2around its rotation axis y. The plate element18has a peripheral edge19which continues the groove profile6of the bending die2, adjacent to its channel17. According to the invention, the plate element18is made up of pieces20,21, in number of two in this embodiment, adapted to be connected to each other after surrounding the bending die2.

The two pieces20,21of the plate element18, after being arranged around the bending die2, are joined to each other with the interposition of a grain22by means of screws23passing through holes24of the two pieces20,21. In particular, the piece20of the plate element18has the shape of a hook and is guided by the bushing13, having a central groove44so as not to interfere with the rotation of the plate element18. The piece21of the plate element18has, in plan view, a trapezoid rounded at the base and is on the opposite side to the bushing13with respect to the die rotation axis y.

Thanks to the fact that the plate element18is free to oscillate around the bending die2, a favorable anti-wrinkle effect is obtained on the elongated workpiece P to be bent. Moreover, as already mentioned, since the plate element18is made in two pieces, it can be mounted on the bending die2to bent to the right and, disassembled and turned upside down, to bend to the left the elongated workpiece P. This is obtained thanks to the longitudinally symmetrical shape of the plate element18and to the fact that the vice3has a plane of symmetry passing through the axis of the fulcrum pin15and for the axis of a clamping screw33, as shown in detail in theFIG.3. Since the axis of the fulcrum pin15is located on the median plane passing through the axis of the bending die2and perpendicular to the trace of the plane α, the vice3can be mounted on the bending die2in a first position and in a second position, after having been rotated by 180° with respect to the first position, in order to be used both for bending in the right and left direction, as mentioned above.

According to the present invention, as shown in detail inFIG.4, the vice3comprises a lower jaw25and an upper jaw26, both opposite each other, in the shape of an L. The lower jaw25and the upper jaw26carry singularly pipe retaining channels indicated generally as27. The lower jaw25is provided at the rear with a through hole28and a fastening screw29for fastening the fulcrum pin15to the lower jaw25of the vice3. The upper jaw26is connected rear to the perforated head16by means of a transverse pin30passing through hinge elements31of the upper jaw26placed on both sides of the perforated head16of the fulcrum pin15. Furthermore, the upper jaw26is provided with a hole32and a clamping screw33of the pipe retaining channels27. The clamping screw33is equipped with a maneuvering rod34.

Frontally, the upper jaw26is provided with pierced ears35,35which are located on both sides of a hooking lever36for clamping the lower jaw25and the upper jaw26. A pin37is retained passing through the pierced ears35,35and the head38of the hooking lever36. The hooking lever36has at its end opposite to the head38a hook39, intended to engage a front recess40of the lower jaw25.

A seat41is formed in the bending die2near its circular segment cut. The seat41, which is present on both sides of the bending die2, in order to allow the bending to the right and to the left, is configured so as to receive a concave insert42which is crossed by the hook-shaped piece20of the plate element18. The concave insert42serves to prevent the elongated workpiece P from being deformed with a bump or crushing at the beginning of the bending step and to create rectilinear continuity between the vice3and the groove of the bending die2Moreover, since it is mounted symmetrically on both sides, in the respective seats41, the concave insert42has the function of allowing the assembly and disassembly of the plate element18to allow the right and left bending, respectively.

Reference will now be made toFIG.5which is a section formed according to a plane with trace A-A ofFIG.3. In this figure the vice3is clearly shown after assembly of its components shown in exploded view inFIG.4. The vice3is in a closing position with the elongated workpiece P between the pipe-retaining channels27.

InFIG.6, which is a cross-section formed according to a plane with trace B-B inFIG.2, it is shown, in particular, that the hook-shaped piece20of the plate element18passes between the bending die2and the bushing13against the central groove44of the latter.

It is understood that the invention achieves the intended purposes. It allows an elongated workpiece to be bent to both right and left without wrinkle formation by a bending die having a single piece structure.