More specifically, this invention refers to a transfer device suitable for use on a block designed to simultaneously grip a batch of semi-finished metal parts and subsequently transfer them for the next stage of permanent deformation by means of cold, warm and hot pressing, as necessary.

This invention can be applied in the mechanical industry sector for the production of standardized parts such as for example bushings, nuts or other items with blind or through holes, extruded or pressed products with standard and special shapes, etc.

BACKGROUND ART It is known that the production of semi-finished parts and/or standardized products by means of cold, warm or hot pressing foresees a work cycle consisting of several stages for the progressive deformation which the pieces undergo.

The work cycle on, for example, mechanical multistation presses is generally carried out simultaneously on a batch of products which are moved rapidly in order to perform the necessary stages.

The transfer of the pieces can not simply be carried

out by means of standard conveyors, for example a belt or carriage conveyor, since the semi-finished parts sometimes need to be handled, for example rotated, in order to ensure rapid and precise performance of the required deformation stage.

At present, machines known as"nut formers"are used for the cold, warm or hot pressing of batches of metal parts, and comprise transfer devices consisting of a block, that can be transferred and in some cases rotated according to requirements, designed to accommodate several pieces being machined.

The block comprises housing bushings, each designed to accommodate a respective station. The station consists of a shank, housed inside the respective bushing in the block, integral with a support body for a fixed collar, often improperly called a gripper.

The term used for collar is associated with its use since it is designed to house the piece being machined and to transfer it, thanks to the simultaneous movement of the entire block, to the next machining stage.

The hollow portion of the fixed collar is shaped according to the external outline of the semi-finished part to be housed, for example it is hexagonal in the typical case of transferring nuts to the last pressing station.

One disadvantage is represented by the fact that fixed collars make"nut former"machines rather inflexible as regards deformation geometries that can be adopted in the different pressing stations and that are advantageous for the metal deformation process, for the quality of the end product and for the life of the equipment specifically used for the pressing.

The concept of transport in fact foresees using only collars in which the product housing is a fixed shape without therefore being able to grip the product in the most advantageous points for the subsequent transfer stage.

The pressing process in the various families of presses, for example the"nut formers", cannot therefore be optimised due to the rather inflexible and penalizing transfer process.

One solution, aimed at making the pressing cycle more flexible in terms of adaptability to complex manipulations that may be carried out on the pieces, has already been proposed with the use for example of machines defined as "nut part formers".

Instead of fixed collars, these machines are equipped with actual grippers with claws that can be opened and closed by means of special mechanical levers.

One disadvantage is represented by the fact that the adjustment of the opening and closing movement of the claws, with the relative setting of the delay or lead times, is achieved by means of complex kinematic motions usually consisting of levers and cam devices that take a long time to adjust each claw according to the product to be pressed.

This system consisting of mechanical levers also takes up a lot of space in the pressing area, considerably increasing the size of the block, the centre distance between one die and the next and the transfer time between one pressing station and the next while reducing the maximum number of pieces per minute that can be produced by the press.

The family of machines called"nut part formers"is in fact slower than the family of machines called"nut

formers".

These mechanisms are therefore particularly cumbersome and unsuitable for use on fast machines such as for example "nut formers".

DESCRIPTION OF THE INVENTION This invention proposes to provide a device for the transfer of semi-finished parts on multistation presses for the process of cold, warm or hot pressing of metals and which can eliminate or significantly reduce the disadvantages described above.

This invention also proposes to provide a transfer device that can be applied to any block of machines for the cold, warm or hot pressing of metals and, in particular, to the family of machines called"nut formers".

This invention also proposes to provide a transfer device that is fully interchangeable with any type of press that works with fixed collar transfer devices ; the invention makes it possible to install from a minimum of one transfer device to a maximum of six or seven transfer devices according to the type of machine and the product to be pressed..

This is achieved by means of a transfer device for semi-finished parts on multistation presses for the process of pressing of metals with the features described in the main claim.

The dependent claims describe advantageous embodiments of the invention.

The device for the transfer of semi-finished parts on multistation presses for the process of pressing of metals according to the invention comprises a station consisting of

a shank, inserted in a respective bushing in a block, integral with a support body for gripping means comprising a gripper equipped with claws that can be moved by a single linear actuator.

According to the invention, the linear actuator is the pneumatic type and comprises a shaft kinematically connected to both claws of the gripper and equipped with end of stroke sensors.

The transfer device is advantageously equipped with an adjustment device to manage the leads and delays of the drive of the actuator with consequent control of the opening and closing of the gripper claws.

The intake and output of compressed air by the actuator can be managed directly by a pneumatic distributor that in combination with the adjustment device, or by a proximity sensor that can be electrically connected to the pneumatic distributor.

The use of a transfer device comprising a single linear actuator ensures rapid execution of the piece gripping and release operations. It also requires normal maintenance activities that are certainly less onerous than devices consisting of complex kinematic cam systems or comprising numerous levers.

The overall dimensions of this transfer device for the various types of machines for cold, warm and hot pressings of metals are very limited while maintaining the dimensions of the pressing area so as to ensure maximum productivity of the press in pieces per minute regardless of whether one or more transfer devices are used in the same block.

DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will become evident on reading the following description of one embodiment of the invention, given as a non-binding example, with the help of the enclosed drawings, in which: figure 1 shows a plan view, in reduced scale, of a traditional type"nut former"machine, comprising a plurality of fixed collar transfer devices housed in a block; figure 2 shows a plan view, with parts in cross- section, of a transfer device according to the invention; - figure 3 is a similar view to figure 1 but with the transfer device equipped with a proximity sensor; figure 4 represents a plan view of a transfer device according to the invention in the open position; and - figure 5 shows a plan view of a transfer device according to the invention in the closed position.

DESCRIPTION OF ONE EMBODIMENT In the figures from 2 to 5, the reference number 10 indicates in general a station of a transfer device, in this case a station 10 of a device for the transfer of semi- finished parts for cold pressing cycles.

The station 10 comprises a shank 11 integral with a support body 12 for a gripper 13 with claws 14 hinged on the body 12.

According to the invention, the shank 11 has a cylindrical configuration and is designed to be housed in a respective bushing 15 in a block 16 (figure 1) of a traditional piece transfer machine, for example a"nut former"equipped with a number of stations 10'and

comprising a kinematic motion 17 for its movement.

The machine illustrated schematically in figure 2 is a "nut former"in which each station 10'is equipped with a transfer element 39 fitted with a collar 40 with a definite shape that cannot be modified other than by replacing the entire transfer body 10'.

The main aim of the invention, therefore, is to replace the entire transfer element 39 of the station 10'with a new transfer element 12 which is part of a station 10, comprising a gripper 13 with a pair of claws 14 that can adapt to the shape of the piece to be transferred.

The body 12 of each station 10 is hollow in order to house a double-acting linear actuator 18 consisting of a pneumatic cylinder 19 and a shaft 20 which projects towards the gripper 13.

Each claw 14, attached to the body 12 by means of a single pin hinge 21, has a portion facing the actuator 18 and presenting a hole 22 designed to accommodate an appropriate kinematic connection with the shaft 20 to ensure the opening and closing of the gripper 13 following the simple translation of the shaft 20.

The free end of each claw 14 is fitted with a wedge 23 configured so as to adapt well to the external outline of the piece 24 to be gripped.

The actuator 18 is pneumatically connected to a distributor 25 by means of pipes 26,27 for the transfer of compressed air coming from any appropriate source.

The distributor 25 can be attached to a guide 28 which slides along the edge of a fixed bed 29; this guide 28 acts as a device to adjust the leads and delays of the drive of the actuator 18 with consequent control of the opening and

closing of the claws 14 of the gripper 13.

As can be seen in figure 3, the transfer device 10 can comprise a proximity sensor 30 directly attached to the guide 28 and electrically connected to the distributor 25 so that it can intervene promptly to indicate the end of stroke positions of the shaft 20.

The block 16 can be electrically connected to an electronic control unit, not shown in the drawings, designed to control the operations of transferring the pieces 24 gripped by the gripper 13 of each station 10.

The block 16 and/or each station 10 can be equipped with sensors designed to detect the presence and/or the correct position of the pieces 24 to be picked up.

With reference to figure 4, it can be noted that the claws 14 of the gripper 13 are placed in the opening position simultaneously and synchronised thanks to the protrusion of the shaft 20 from the cylinder 19 of the linear actuator 18.

As can be seen in figure 5, the return of the shaft 20 inside the respective cylinder 19 leads to the closure of the claws 14 on the piece 24 ensuring its transfer to the subsequent machining stages.

According to an embodiment not shown in the drawings, but easily imaginable from them, the linear actuator 18 can be the single-acting type with, in this case, the support body 12 equipped with means of elastic loading for the return of the claws 14 from the open position to the closed position on the piece 24.

According to another embodiment not shown in the drawings, but easily imaginable from them, the pneumatic distributor 25 shown in figures 2 and 3 can be replaced by a

unit to control a system of electromechanical movement that is housed in the same cavity as the cylinder 19 visible in these figures. This electromechanical system presents fixed equipment, electrically connected by appropriate electrical connection means to the control unit and mobile equipment which is constrained to the shaft 20 which, in turn, acts on the claws 14 to open and close them.

The shank 11 of the transfer device 10 is a standard shape and size so that it can be housed in the respective bushing 15 of any block 16 used in machines for cold, warm or hot pressing, thus being perfectly interchangeable with traditional transfer devices.

It is therefore possible and very economical to equip a traditional machine, for example the"nut former"type, with one or more transfer device kits according to the invention, allowing the machine to be used and maintaining maximum productivity in pieces per minute also for machining mechanical parts other than, for example, hexagonal nuts.

The invention is described above with reference to a preferred embodiment. It is nevertheless clear that the invention is susceptible to numerous variations, within the framework of technical equivalents.