Background art Bending brakes generalty comprise a structure supporting twc opposing toolplates positioned substantially in the same vertical plane, and of which one toolplate can move vertically.

To the facing edges of the toolplates are fixed the means for retaining and locking the upper tool (usually the so-called punch) and the lower tool (usually the so-called die) respectively, each of these being formed from a plurality of tools aligned in succession, they having the same cross-section but different lengths.

The tool locking means are fixed to the respective toolplates by known means, and are arranged to receive the tool shank by insertion and to lock it in the desired position.

With particular reference to the means which supports and locks the lower tool (die), this is of overall elongate shape along a horizontal axis, and comprises, parallel to the unit axis, a full- length longitudinal slot with its concavity facing upwards, to receive as an exact fit the lower portion of a tool or a series of tools.

The lower portion of the currentlyinsertedasanexactis fit into the longitudinal slot and is clamped by transverse screws passing through holes provided in a side wall of the locking means, to act via their end against one side of the toot.

These screws are tightened manually against the too', using andsufficientlyprecisetighteningforces.relativelylarge

Because of the different types of work involved, frequent changing of moortoolsisrequired,eachtimeinvolvingmanualor slackening and subsequent tightening of the screws, these <BR> <BR> <BR> <BR> representing relatively lengthy manual procedures. This drawback is made more serious by the fact that the locking means must in practice be able to clamp even a single tool of relatively short length, so that a relatively large number of camping screws is required.

Moreover the contact surface between the screws and tool is relatively small, resulting in relatively high pressure on the end of the screws which with use can easily deform and cause malfunctioning.

An object of the invention is to overcome said drawbacks by a locking unit of rapid and simple mechanized operation.

A further object is to provide a locking unit which operates reliably and effectively.

Disclosure of the invention These and further objects are attained by the unit of the invention as characterised in the claims.

The invention is based on the fact of comprising a base piece and a first jaw means positioned parallel and side by side to together define said longitudinal slot, the first jaw means being connected to the base piece in such a manner as to be able to rotate about an axis parallel to the unit axis in the sense of increasing and respectively decreasing the width of the longitudinal slot. The unit also comprises a second jaw means acting within said longitudinal slot, and actuator means associated with the first jaw means and acting on the second jaw means with a transverse thrust thesenseofurgingthesecondjawmeanstowardsthedirectedin interior of the longitudinal slot. Rection means are also provided, associated with the first jaw means, to produce a reaction tending to rotate the first jaw means in the sense of decreasing the width of the longitudinal slot. Moreover, both the thrust with which said actuator means operate and the thrust with which the reaction means operate are such as to lock the tools.

The invention is described in detail hereinafter with the aid of the accompanying figures, which illustrate one embodiment thereof by way of non-toting example.

Figure 1 is an overall perspective view of a press to which the locking unit of the invention is applied.

Figure 2 is a perspective view of the locking unit of the invention.

Figure 3 is a a front view in the direction of the arrow III of Figure 2.

Figure 4 is a perspective view of Figure 2 from below.

Figure 5 is a section on the plane V-V of Figure 3.

Figures 6A and 6B are sections on the plane VI-VI of Figure 3.

Figures 7A and 7B are sections on the plane VII-VII of Figure 3.

Figures 6A, 7A relate to the case in which a lower tool (die) provided with a lower shank projecting downwards from the bottom of the tool is associated with the unit.

Figures 6B, 7B relate to the case in which a lower tool (die) not provided with a lower shank is associated with the unit.

The upper toolplate 2 lowerly carries a series of aligned upper tools 4 of the same cross-section but of different lengths, which overall form the press punch. Likewise the fixed lower toolplate 3 carries a series of aligned lower tools 10 forming the press die.

Specifically, the upper tools 4 and lower tools 5 are secured to the respective toolplates 2 and 3 by respective locking units indicated by 5 and 7 respectively, these being secured to the respective toolplate 2 and 3 by means of known type.

This invention relates in particular to the lower locking unit 7, the ensuing description being relative thereto. The invention can however also be used for the upper unit after applying appropriate modificattons.

The unit 7 is of overall elongate form along a horizontal axis parallel to the upper edge of the lower toolplate 3, and comprises a full-length longitudinal slot 8 parallel, to the unit axis, to receive as an exact fit the lower portion of a series of tools 10 (or of a single tool 10).

The tools 10 are of two types, namely a first type. indicated by

10a, having a lower portion 11, and a lower shank 12 of width less than the portion 11 and projecting downwards from the portion li : and a second type, indicated by 10b, having a flat lower portion without a lower shank.

The unit of the invention comprises a base piece 15 and a first jaw means 20 positioned parallel and side by side to together define said longitudinal slot 8.

In a preferred (but not exclusive) embodiment, the base piece 15 is a single piece extending along the entire length of the upper edge of the lower toolplate 3, whereas the first jaw means 120 is compose of a plurality of separate identical aligned modular pieces 21 all applied to the base 15. Alternatively, the jaw means 20 can comprise a full-length single piece instead of a series of aligned pieces 21.

Each component piece 21 of the first jaw means 20 is connected to the base piece 15 in a manner enabling it to rotate about an axis parallel to the unit axis in the sense of increasing or decreasing the width of the longitudinal slot 8.

In a preferred (but not exclusive) embodiment, each component piece 21 of the first jaw means 20 is of prismatic shape, is of flexible elastic material (in particular steel), and is divided into an upper portion 22'and a lower portion 22"by a horizontal transverse longitudinal cut 23 extending along the entire width of the piece 21 except for a narrow band 24 defining a hinge region within which the axis about which the upper portion 22'rotates relative to the lower portion 22"is defined. The lower portion 22"is rigidly fixed to the base piece 15 by screws 26 of horizontal transverse axis (see Figures 7A and 7B in particular) and also by centering pins 27 likewise of horizontal transverse Figure5inparticular).Byvirtueoftheintrinsicaxis(see elasticity of the band 24, the upper portion 22'is able to rotate, through a (relatively small) predetermined angle, about the axis defined by the band 24, in the sense ot increasing or decreasing the width of the longitudinal slot 8.

In thebasepiece15hasaportion15ajoinedtotherespect, lower portion 22"by receiving the ends of the screws 26, and

having a vertical flat face 151 in contact with the portion 22".

The cut 23 is horizontal, the band 24 being adjacent to the face 151 at an intermediate level along the height of this latter.

The amount through which the upper portion 22'rotates towards the longitudinal slot 8 is limited by the contact between the lower region of said portion 22'and the face 151 of the base piece 15; there is hence an inward rotation 7imit.

The cut 23 comprises an initial rectilinear narrow part which terminates, before reaching the band 24, in a circula part provided to prevent triggering of fractures.

A thin layer of rigid material 231 is provided within the initial rectilinear portion of the cut 23 to limit the rotation of the upper portion 22'in the withdrawal direction from the longitudinal slot 8, to prevent breakage of the piece 21 caused by excessive rotation; there is hence an outward rotation 7imit.

Fluid-operated actuator means 30, having a piston 31 facing said longitudinal slot 8, are associated with the first jaw means 20 to act with a transverse thrust urging the piston 31 towards the interior of the longitudinal slot 8.

There is also provided a second jaw means 16 acting within the longitudinal slot 8 and, in a preferred (but not exclusive) embodiment, consisting of a series of aligned prismatic pieces 17 of rectangular cross-section, one for each component piece 21, giving rise to a single body alongside the first jaw means 20 and extending along the entire length thereof. This series of pieces 17 partly fills the lower portion of the longitudinal slot 8, to define therein an upper channel 81 as wide as the longitudinal slot 8, and a more narrow lower channel 82 positioned below and communicating with the upper channel (see Figure 5 in particular). secondjawmeans16canbeasinglefull-lengthAlternatively,the piece instead of an aligned series of pieces 17.

Each piece 17 is joined to the upper portion 22'by horizontal transverse pins 18 having their front end engaged in the piece 17 and their rear shank slidable within a hole 181 provided in the portion 22'. The shank 182 has a wide head which retains a spring 183 compressed against the end wall oz'the nole 181. Tne spring

183 tends to pull the piece 17 into contact with the upper portion 22'.

The actuator means 30 are interpose between the first jaw means 20 and the second jaw means 16 so that when activated they move the pieces 21 and 17 apart.

In detail, each actuator means 30 (see Figure 6A in particular) comprises a guide bush 32 inserted into a cylindrical cavity 33 provided in the upper portion 22'and opening into the longitudinal slot 8 at the piece 17. The bush 32 is in sealed contact with and rigidly fixed to the cylindrical surface of the cavity 33, its through bore sealedly housing a piston 31 facing and in contact with the piece 17. At its rear end the piston 31 has a wide head retaining a spring 34 compressed against the guide bush 32. The spring 34 tends to urge the piston 31 into the cavity 33.

The rear region of the cavity 33 of each actuator means 30 is connected to a system of pressurized oil feed conduits.

Said system comprises a main header 41 extending parallel to the axis of and along the entire length of the unit 7, and in particular fixed and embedded into the base piece 15 along that face opposite the face to which the first jaw means 20 is applied.

From the header 41 there extend various transverse tubes 42, one for each actuator means 30, they being housed in transverse grooves 43 provided m the lower surface of the lowest portion of the part 15. Said tubes 42 are at least slightly flexible in order to follow the rotation of the upper portion 22'.

Reaction means 50 are associated with the first jaw means 20 to produce an adjustable reaction tending to rotate the first jaw means 20 (see Figure 7A in particular).

Said reaction means 50 each comprise a series of compression-acting cuphousedprecompressedinarespectivesubstantially51 vertical hole 52 provided in the upper portion 22'of the first jaw means 20 and opening into the cut 23 against the upper face of the lower portion 22". The series of springs 51 is supporte by a guide stem 53 and is compressed between the upper face of the lower portion 22". on which the stem 53 rests, and a threaded plug 54 engaged in the top of the hole 52.

The reaction produced by the precompressed springs 51 tends to rotate the upper portion 22'about the hinge band 24, in that direction (anticlockwise) which decreases the width of the longitudinal slot 8.

The lower channel 82 of the slot 8 is arranged to receive as an exact fit the lower shank 12, projecting downwards from the lower <BR> <BR> <BR> <BR> portion 11, of a tool or series of tools 10a. Likewise said upper channel 81 is arranged to receive as an exact fit the lower portion 11 of a tool or series of tools 10b not possessing a lower shank.

If a series of tools 10a provided with a shank 12 are to be used, this is inserted into the lower channel 82, after which pressurized oil is fed to the actuator means 30 to cause the pistons 31 to move towards the longitudinal slot 8, with the result that the pieces 17 are pressed against the shank 12 to press it against the base piece 15 with a force sufficient to properly lock it. During this stage, the thrust produced by the actuator means 30 tends to withdraw the upper portion 22'from the longitudinal slot 8, this action being opposed by the reaction of the springs 51.

To release the tool 10a, pressure is removed from the actuator means 30, causing the locking thrust on the shank 12 to cease. The amount through which the upper portion 22'rotates towards the longitudinal slot 8 by the action of the springs 51 is limited by the contact between the lower region of said portion 22'and the face thebasepiece15(inwardrotationlimit).Thechannelof 82 hence widens and the shank 12 can be extracted without effort.

If the unit of the invention is to receive a tool 10b not provided with a lower shank, each component piece 21 is provided with a complementary filler piece 19 which completely fills the width of the lower channel 82. In this case, the lower portion 11 of the tool 10b totally occupies the width of the upper channel 81.

Moreover the upper part of the inner lateral face 221 of the upper portion 22', which acts against the lower portion 11 of the tool 10b, projects at least a small distance (a few hundredths of a millimetre) towards the interior of the upper channel 81 relative to the lower part of the face 221, to make contact with the tool 10b before the upper portion 22'reaches its in, çard rotation 1i. wit.

To lock the tool, in this case pressure is removed from the actuator means 30. This means that the upper portion 22'is subjected only to the action of the springs 51, which cause it to rotate towards its inward rotation limit, and hence to push against the side of the tool 10b, with a force sufficient to properly lock the tool 10b.

To release the tool 10b, the actuator means 30 are pressurized. In this case, as the thrust with which the actuator means operate is such as to cause the first jaw v means 20 to rotate rearwards by overcoming the thrust produced by the reaction means 50, the upper portion 22'rotates as far as its outward rotation limit, with the result that the tool is released from its grip.

By applying suitable modifications, the unit of the invention can equally be used for the upper tool 4.

Numerous modifications of a practical and applicational nature can be made to the unit of the invention, but without leaving the scope of the inventive idea as claimed below.