Movable head for a stretching machine

Abstract

A movable head (1, 1a) for a stretching machine for sheets or plates has a front portion (2, 2a) including sheet segments (3, 3a) parallel to one another and shaped so as to define a clamping mouth (18) and a stretching plane (XY) orthogonal to the sheet segments (3, 3a), wherein the mouth (18) comprises clamping means to lock a sheet (P) or plate, so that a traction force (F) parallel to the stretching plane (XY) is applicable thereto, a rear portion (4, 4a) firmly connected to the front portion (2, 2a) so as to stiffen the front portion (2, 2a), and stiffening tie-rods (20), arranged parallel to the stretching plane (XY) for connecting the front portion and the rear portion (2, 4; 2a, 4a) to each other.

Claims

1. A movable head for a stretching machine for sheets or plates, said movable head comprising: a front portion including a plurality of sheet segments parallel to one another and shaped so as to define a clamping mouth provided with an opening facing a front surface of said front portion, said opening being defined by two reciprocally opposite lips so as to define a stretching plane orthogonal to said sheet segments and equally spaced apart from said lips, said clamping mouth comprising clamping means to lock said sheet or plate passing through said opening of said clamping mouth, so that a traction force parallel to said stretching plane is applicable to said sheet or plate, a rear portion firmly connected to said front portion so as to stiffen said front portion, wherein the front portion has an abutment surface which is in abutment with an abutment surface of the rear portion; and wherein said front portion and said rear portion are rigidly connected to each other by means of a plurality of stiffening tie-rods, arranged parallel to said stretching plane and parallel to said traction force when the traction force is applied, and orthogonal with respect to the abutment surface of the front portion and to the abutment surface of the rear portion, so that the plurality of stiffening tie-rods prevents relative movements between the front portion and the rear portion.

2. A movable head according to claim 1, wherein said front portion comprises a first block and a second block opposed to each other with respect to the stretching plane and orthogonally extended with respect to said sheet segments, each sheet segment of said plurality of sheet segments being firmly restrained to said first block and second block.

3. A movable head according to claim 2, wherein each sheet segment of said plurality of sheet segments is welded to said first block and second block.

4. A movable head according to claim 2, wherein each stiffening tie-rod of said plurality of stiffening tie-rods extends between said rear portion and one of said first block and second block.

5. A movable head according to claim 2, wherein each of said first block and second block comprises, respectively, a shoulder butted up against an abutment provided on said rear portion.

6. A movable head according to claim 5, wherein, between each of said first block and second block and said rear portion, said movable head comprises at least one cavity in which at least one taper key is housed.

7. A movable head according to claim 1, wherein each stiffening tie-rod of said plurality of stiffening tie-rods extends between said rear portion and at least one of said sheet segments.

8. A stretching machine comprising a movable head according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further features and advantages of the present invention will become more evident from the following detailed description of a preferred but non exclusive embodiment thereof, made by way of a non-limiting example with reference to the accompanying drawings, in which:

(2) FIG. 1 shows an axonometric view of a movable head of a stretching machine according to the present invention;

(3) FIG. 2 shows a side sectional view of the movable head in FIG. 1;

(4) FIG. 3 shows a side view of two components of the movable head in FIG. 1;

(5) FIG. 4 shows a top plan view of the components in FIG. 3;

(6) FIG. 5 shows a detailed side view of the movable head in FIG. 1 in an operating configuration thereof;

(7) FIG. 6 shows a side sectional view, corresponding to that in FIG. 2, of a possible embodiment variant of the present invention;

(8) FIG. 7 shows a side sectional view, corresponding to that in FIG. 2, of the embodiment variant in FIG. 6;

(9) FIGS. 8a-b show two respective enlarged views of detail VIII in FIG. 6, in two respective operating configurations;

(10) FIGS. 8c-e show three views, corresponding to that in FIG. 8b, of three respective embodiment variants of the present invention;

(11) FIG. 9 shows an axonometric view of an embodiment variant of the movable head in FIG. 1;

(12) FIG. 10 shows a side sectional view, corresponding to the view in FIG. 2, of the movable head variant in FIG. 9.

(13) The same reference numerals in the figures denote the same elements or components.

DETAILED DESCRIPTION OF THE INVENTION

(14) With reference to the accompanying drawings, a movable head applicable to a stretching machine (not shown as a whole) for sheets or plates or other similar products is indicated as a whole with reference numeral 1 (FIGS. 1-8e). An embodiment variant of the movable head according to the present invention is indicated as a whole with reference numeral 1a (FIGS. 9 and 10).

(15) A stretching machine typically comprises a pair of movable heads arranged so as to grip two opposite edges of the same material to be stretched, e.g. a sheet P, by applying two respective and opposite traction forces.

(16) With initial reference to the accompanying FIGS. 1-8e, the movable head 1 comprises a first front portion 2 and a second rear portion 4, firmly restrained to each other.

(17) The first portion 2 includes a plurality of sheet segments 3 identical in shape, arranged so as to be parallel to one another and spaced apart along a longitudinal direction, orthogonal to the sheet segments 3 themselves.

(18) Each sheet segment 3 comprises two main surfaces 6a,b reciprocally opposite and a lateral edge surface 7 extended between the main surfaces 6a,b along the thickness of the sheet segment 3. The edge surface 7 comprises a front side 11 and an opposite rear side 12, parallel to the front side 11. The edge surface 7 further comprises two sides 13a,b, respectively upper and lower sides, parallel to each other and orthogonal to the front and rear sides 11, 12. Two chamfers 14a,b are provided between the front side 11 and the two sides 13a,b, respectively. Two shoulders 12a,bupper and lower shouldersare provided on the rear side 12, adjacent to the two upper and lower sides 13a,b, respectively. A central stretch 12c of the rear side 12 is therefore defined between shoulders 12a,b, which stretch projects with respect to shoulders 12a,b and is connected thereto by means of two respective upper and lower sides 17a,b, respectively.

(19) Close to the front side 11, each sheet segment 3 comprises a through hole 15 having an axis orthogonal to the main surfaces 6a,b of the sheet segment 3 and a connecting passageway 16 between the hole 15 and the front side 11.

(20) All the sheet segments 3 are placed side by side so that the respective holes 15, aligned along a common transversal axis Y, form a clamping mouth 18 provided with an opening 10, consisting of the set of the respective passageways 16 of the sheet segments 3. Opening 10 faces a front surface 19 consisting of the envelope of the front sides 11 of the sheet segments 3. Opening 10 is defined by two lips 10a,b opposite to each other so as to define a longitudinal axis X, orthogonal to the transversal axis Y and equally spaced apart from lips 10a,b of opening 10.

(21) The longitudinal X and transversal Y axes form a stretching plane XY orthogonal to the sheet segments 3, which are shaped so as to be symmetrical to the stretching plane XY, as described above.

(22) Clamping means 31a,b are provided inside mouth 18, comprising a pair of wedges 31a, opposite to the stretching plane XY, and movable towards the stretching plane XY for locking an edge of sheet P passing through the opening 10 in mouth 18, so that a traction force F lying on the stretching plane XY and parallel to axis X can be applied to sheet P. Wedges 31a are movable along two respective surfaces 31, inclined with respect to the stretching plane XY. On the side facing the stretching plane XY, each wedge 31a carries a respective clamping plate 31b, apt to abut against the edge of sheet P so as to lock it by friction into mouth 18. At the end of the stretching operations, the clamping means are moved away from the stretching plane XY, so as to allow sheet P to be released through opening 10. The first portion 2 of the movable head 1 further comprises a first and a second block 21, 22, parallelepiped in shape, opposite to each other with respect to the stretching plane XY and orthogonally extended with respect to the sheet segments 3. Each block 21, 22 comprises a plurality of through holes 26 (in the examples of the accompanying FIGS. 1-8e, three holes for each block 21, 22), arranged parallel to the transversal axis Y. Each sheet segment 3 is next to blocks 21, 22 so that the upper shoulder 12a and the upper side 17a are next to the first block 21 while the lower shoulder 12b and the lower side 17b are next to the second block 22. The size of blocks 21, 22 in a side view orthogonal to the sheet segments 3 (FIGS. 2 and 3) is equal to the length of shoulders 12a,b and of sides 17a,b, so that both blocks are aligned with the central stretch 12c of the rear side and aligned with the upper and lower sides 13a,b of each sheet segment 3, respectively. The sheet segments 3 are firmly restrained to the first and second blocks 21, 22, for example by welding along each one of shoulders 12a,b and sides 17a,b.

(23) In other embodiment variants of the present invention (FIGS. 6, 7 and 8a-e), two shoulders having the same width are provided on each one of blocks 21, 22, respectively, which shoulders identify two respective portions farther from the stretching plane XY, 21a, 22a, facing the second portion 4. Two sides 21b, 22b, parallel to the stretching plane XY are defined between the respective portions of blocks 21, 22 closer to the stretching plane XY and shoulders 21a, 22a, respectively.

(24) The second portion 4 of the movable head 1 consists of a central body 40 and of two tabs 41. The central body 40 has an overall size almost equal to that of a parallelepiped with front surface 40a abutted against the central stretch 12c of the rear side 12 and against the blocks 21, 22 of the front portion 2. Each tab 41 supports a respective hollow cylinder 42 provided with a respective through hole 43 with axis parallel to the longitudinal axis X. Through holes 43 accommodate two respective cylinders, for example two hydraulic cylinders (not shown), which move the movable head 1 for transmitting the traction force F to sheet P.

(25) In the embodiment variants in FIGS. 6, 7 and 8a-e, the central body 40 comprises two projecting stretches 51a, 52a, apt to abut in coupling (FIG. 7) against the two shoulders 21a, 22a, respectively. The projecting stretches 51a, 52a have a shorter length than the respective shoulders 21a, 22a, so that two respective cavities 53, 54 are defined between the sides 21b, 22b of shoulders 21a, 22a and the two respective sides 51b, 52b of the projecting stretches 51a, 52a so as to facilitate, in the assembly step, the coupling between the front and rear portions 2, 4 of the movable head 1. The clearance at cavities 53, 54 is eliminated by using wedges accommodated therein. In a first variant (FIG. 8b), two taper keys 61, 62 are provided in each cavity 53, 54. The taper keys are arranged so that the respective oblique sides are facing towards each other. In a second variant (FIG. 8c), sides 51b, 52b are inclined with respect to the stretching plane XY, so that cavities 53, 54 have a triangular section. In such a second variant, a single taper key 63 is accommodated in each cavity 53, 54. In a third variant (FIG. 8d), two pairs of taper keys 64a,b and 65a,b placed side by side are provided along sides 21b, 22b and 51b, 52b. In each pair 64a,b and 65a,b, the two keys are facing towards each other, as in the first variant in FIG. 8b. In a fourth variant (FIG. 8e), sides 51b, 52b have a triangular profile and are apt to abut with the respective vertexes against sides 21b, 22b, so as to divide each cavity 53, 54 into two respective portions with triangular section, in which two taper keys 66, 67 are accommodated, respectively.

(26) With reference to the accompanying FIGS. 9 and 10, the movable head 1a differs from the above-described movable head 1 in that it does not comprise welded sheet segments but bolted sheet segments, thus allowing the stretching machine to have larger dimensions or to prevent welds from being carried out under critical circumstances, e.g. if the thickness or the material of the sheet segments is difficult to be welded. This is obtainable by means of a first front portion 2a comprising a plurality of sheet segments 3a, but free from blocks 21, 22. The sheet segments 3a are directly couplable to a second rear portion 4a of the movable head 1a. Accordingly, in the production steps prior to the assembly of the first front portion 2a with the second rear portion 4a, the sheet segments 3a may be individually handled. This allows the sheet segments 3a to be made with larger dimensions than the sheet segments 3 of the movable head 1 and accordingly, as a whole, it is possible to make the movable head 1a with larger dimensions than the movable head 1, in which the sheet segments 2 need to be first welded to blocks 21, 22. Moreover, the absence of welds allows the sheet segments 3a to be made of alloyed steel (such as EN10250-3 30CrNiMo8 or EN10025-6 S690Q) compared to that of the sheet segments 3. At the front side 11, the sheet segments 3, 3a are morphologically identical, all comprising a respective hole 15, so as to form the mouth 18 when a plurality of sheet segments is aligned to form the front portion 2, 2a. Each sheet segment 3a further comprises a plurality of through holes 76 (in the example of the accompanying FIGS. 9 and 10, six holes for each sheet segment, symmetrically distributed with respect to the longitudinal axis X), arranged parallel to the transversal axis Y. The second portion 4a of the movable head 1a consists of a central body 60 and of two side portions 61, each comprising a pair of tabs 61a,b. The central body 60 is internally hollow and has an overall size almost equal to a parallelepiped. The central body 60 is provided with a front surface 60a abutting against a rear side 72 of each sheet segment 3a. The front surface 60a, in the two farthest portions from the stretching plane XY, is provided with two shoulders 74a,b, symmetrical with respect to the stretching plane XY. Shoulders 74a,b are respectively apt to abut in coupling (FIG. 10) against two projecting stretches 72a,b of the rear side 72 of each sheet segment 3a. According to a different embodiment variant (not shown), shoulders 74a,b are obtained on the sheet segments 3a while the two projecting stretches 72a,b are placed on the front surface 60a. Each pair of tabs 61a,b is apt to be coupled to a supporting structure (not shown and not described as it is not an object of the present invention).

(27) In all the embodiment variants, the second rear portion 4, 4a is firmly connected to the first front portion 2, 2a by means of a plurality of stiffening tie-rods 20, arranged parallel to the stretching plane XY. Each tie-rod 20 connects the first portion 2, 2a to the second portion 4, 4a, respectively.

(28) With reference to the accompanying FIGS. 1-8e, each tie-rod 20 extends between a first end 20a firmly restrained to the first or second block 21, 22, by means of a respective locking nut accommodated in one of the through holes 26, and a second end 20b projecting with respect to a respective abutment surface 45, orthogonal to the stretching plane XY, provided in the second rear portion 4. A nut 25 is provided at the second end 20b, which nut abuts against the respective surface 45, for imparting the required stretching status to the respective tie-rod 20. According to other embodiment variants (not shown), each end 20a is firmly restrained to the first or second block 21, 22 in a different manner, e.g. by using a tie-rod consisting of a biting screw with its end 20a screwed in a respective hole provided in the first or second block 21, 22.

(29) With reference to the accompanying FIGS. 9, 10, each tie-rod 20 extends between a first end 20a firmly restrained to one of the sheet segments 3a by means of a respective locking nut accommodated in one of the through holes 76, and a second end 20b projecting with respect to a respective abutment surface 75, orthogonal to the stretching plane XY, provided in the second rear portion 4a.

(30) In general, in all the embodiment variants, for the purposes of the present invention, the overall load applied to tie-rods 20, i.e. the sum of the loads applied to every single tie-rod, must be greater than the traction force F applied to sheet P.

(31) In the different embodiment variants of the present invention, the number of tie-rods 20 depends on the dimensions of the movable head 1 and in particular on the front interface surface 40a between the front and rear portions 2, 4, so as to ensure an even stretching status in all the sheet segments 3.

(32) In all the examples of the accompanying FIGS. 1-10, the tie-rods are arranged according to rows orthogonal to the stretching plane XY.

(33) In the embodiment variants in FIGS. 1-8e, eight rows of six tie-rods 20 each are provided, for a total of 48 tie-rods, i.e. 24 active tie-rods on each one of blocks 21, 22. In the embodiment variant of the accompanying FIGS. 9 and 10, a row of six tie-rods 20 is provided for each sheet segment 3a.

(34) In all the embodiment variants of the accompanying FIGS. 1-10, in each row the tie-rods are symmetrically distributed with respect to the stretching plane XY (in the example of the accompanying figures: six tie-rods 20 for each row, three tie-rods 20 above the stretching plane XY and three tie-rods 20 beneath plane XY). In some variants of the present invention, as shown in FIG. 2 and FIG. 10, in each row the tie-rods 20 which are farther from the stretching plane XY are shorter than the four tie-rods 20 which are closer to the stretching plane XY. Such a choice is determined by the fact that blocks 21 and 22, in their respective parts farther from the stretching plane XY, are compressed, and accordingly the corresponding part of the rear portion 4 is not required to impart a particular stiffness, i.e. the respective abutment surface 45 may be closer to the front surface 40a.

(35) According to another embodiment variant (not shown), tie-rods 20 have all the same length. In general, the length of tie-rods 20 may be selected, in the different embodiment variants of the present invention, so as to ensure the stiffness required for the correct operation of the movable head 1.

(36) The described technical solutions allow the intended task and objects to be fully achieved with reference to the mentioned prior art, thus achieving a plurality of further advantages.

(37) Among these, the movable head 1 allows a stretching machine to be implemented, consisting of only two main portions 2, 4, individually movable, constrained to each other in a permanently stiff manner. Alternatively, according to the present invention, the movable head 1a allows a stretching machine to be implemented, in which each sheet segment 3a of the front portion 2a is directly constrainable to the rear portion 4a. Therefore, the latter solution is characterized by a larger number of elements to be moved for obtaining the final assembly, but this allows larger elements to be managed, thus obtaining a larger stretching machine as compared to the solution with welded sheet segments or to a stretching machine with sheet segments made of alloyed steel which are difficult to be welded.