TECHNICAL FIELD OF THE INVENTION

The present invention concerns a hydraulic plant for presses, in particular for 5 presses for manufacturing ceramic products, for example ceramic tiles.

STATE OF THE ART

Known hydraulic plants for presses for ceramic products usually comprise an electric motor group that actuates a hydraulic pump so as to supply the pressurised oil for the different actuations of the press, and in particular to actuate the presser l o unit of the products.

In particular, such a presser unit comprises a hydraulic cylinder or even, in some cases, many cylinders arranged in parallel.

The hydraulic actuation system of the presser unit of the press is normally called hydraulic power pack.

15 In presses for manufacturing ceramic products the hydraulic power pack for actuating the presser unit is, as can be understood, one of the main components of the machine, the operation and performance of which heavily influence the behaviour and the characteristics of the entire apparatus.

Indeed, the presser unit is clearly the main mechanical member of the machine, 20 and its possible failure or malfunction, as well as the failure or malfunction of its hydraulic actuation system, can force the entire production to be stopped even for extended time periods.

Moreover, considering the flow rates and the pressures of the oil involved, the actuation of the presser unit represents the member of the machine that requires 25 the greatest amount of energy in order to be able to operate correctly: consequently, its energy efficiency is of primary importance in the design of the apparatus in order to be able to contain its management costs within acceptable limits.

PURPOSES OF THE INVENTION

30 The task of the present invention is to improve the state of the art in the field of presses for manufacturing ceramic products.

In such a technical task, a purpose of the present invention is to devise a hydraulic plant for presses, in particular for manufacturing ceramic products, which allows to considerably limit the drawbacks due to the possible stopping of the machine for maintenance reasons of the hydraulic plant itself.

Yet another purpose of the present invention is to provide a hydraulic plant for presses, in particular for manufacturing ceramic products, that is more energy efficient with respect to known hydraulic plants.

A further purpose of the present invention is to devise a hydraulic plant for presses, in particular for manufacturing ceramic products, having more versatile actuation and operation compared with known plants.

Such a task and such purposes are all accomplished by a hydraulic plant for presses, in particular for manufacturing ceramic products, according to what is foreseen in the attached claim 1.

The hydraulic plant for presses, in particular for presses for manufacturing ceramic products of the type comprising a presser unit provided with at least one hydraulic cylinder for pressing products, comprises, according to the invention, a plurality of hydraulic power packs for actuating the presser unit, connected to one another in parallel, adapted to send a flow of pressurised oil to the hydraulic cylinder that can be varied relative to the different operating needs of the press.

The dependent claims refer to preferred and advantageous embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention will become clearer from the description of an embodiment of a press, illustrated for indicating purposes in the attached drawings, in which:

figure 1 is a functional diagram of the hydraulic plant according to the invention associated with a press for ceramic products.

EMBODIMENTS OF THE INVENTION

With reference to the attached figure 1, a hydraulic plant for presses, in particular presses for manufacturing ceramic products, according to the present invention, is wholly indicated with 1.

In figure 1 the hydraulic plant 1 is illustrated associated with a press for ceramic products, for example ceramic tiles, wholly indicated with 2.

For the purposes of the present invention, what is most relevant is the fact that the press 2 is of the type comprising a presser unit 3 provided with at least one hydraulic cylinder 4 for pressing products.

The hydraulic cylinder 4 can, without distinction, be of the simple effect type or of the double effect type.

The presser unit 3 of the press 2 can also comprise more hydraulic pressing cylinders 4 arranged in parallel, in relation to the specific application needs.

According to an aspect of the present invention, the hydraulic plant 1 comprises a plurality of hydraulic power packs for actuating the presser unit 3, respectively indicated with 5a,5b,5c,5d.

The hydraulic power packs 5a,5b,5c,5d are connected together in parallel.

The aforementioned hydraulic power packs 5a,5b,5c,5d are adapted to send a flow of pressurised oil to the hydraulic cylinder 4 of the presser unit 3 that can be varied relative to the different operating needs of the press 2, as will be made clearer hereafter.

In greater detail, according to another aspect of the present invention each of the hydraulic power packs 5a,5b,5c,5d comprises a fixed flow rate pump associated with a respective alternating current electric motor.

The aforementioned pump can for example be of the type with axial pistons, or of the type with radial pistons, or of any other type technically suitable for the present application.

According to a further aspect of the present invention, each alternating current electric motor of the power packs 5a,5b,5c,5d is operatively slaved to a respective inverter for adjusting the rotation speed of the respective pump.

The adjustment of the speed of each electric motor through an inverter, and therefore of the respective pump, makes it possible to vary the flow rate of oil supplied by each power pack 5a,5b,5c,5d and sent to the presser unit 3 of the press 2, with the effects that will be made clearer hereafter.

Each hydraulic power pack 5a,5b,5c,5d is, or can be, provided with further components such as a pressure limiting valve, a tank, an accumulator, a filter, a heat exchanger, and/or other.

According to yet another aspect of the invention, the hydraulic power packs 5a,5b,5c,5d provided in the hydraulic plant 1, connected in parallel, are four in number.

The number of power packs 5a,5b,5c,5d present in the plant 1 can be varied according to specific application needs.

Each of the hydraulic power packs 5a,5b,5c,5d is connected to a respective pressurised oil delivery branch 6a,6b,6c,6d; each delivery branch 6a,6b,6c,6d is in turn connected to a pipe 7 for supplying oil to the presser unit 3, i.e. to the hydraulic cylinder 4.

According to another aspect of the invention, the plant 1 comprises a central control unit 8.

The central control unit 8 is operatively connected to the hydraulic power packs 5a,5b,5c,5d.

The central control unit 8 can, for example, consist of a programmable logic controller (PLC), or another equivalent control device.

The control unit 8 can be exclusively dedicated to controlling the hydraulic power packs 5a,5b,5c,5d and thus designed and installed for this purpose, or it can consist of the same controller already present in the press 2, suitably reprogrammed to manage the operation of the power packs 5a,5b,5c,5d.

The central control unit 8 is suitable for managing and controlling the operation of each of the hydraulic power packs 5a,5b,5c,5d independently from each other, with the technical advantages that will become clearer hereafter.

In greater detail, the central control unit 8 is adapted to exclude the operation of each of the hydraulic power packs 5a,5b,5c,5d independently from one another. This last characteristic is particularly advantageous for many reasons. Firstly, if one of the power packs 5a,5b,5c,5d should fail, even temporarily, or needs programmed or extraordinary operations of maintenance and/or of replacement of parts, it can be quickly and easily isolated in order to be able to carry out the required interventions without having to interrupt the work cycles of the press 2.

Moreover, in the case in which the flow rate required by the press 2 during its operation is less than that one potentially deliverable by the plant 1 with all of the power packs 5a,5b,5c,5d operating, one or more of the power packs 5a,5b,5c,5d can be excluded, even temporarily.

In particular, the electric motors of the power packs 5a,5b,5c,5d that are not intended to be used can be stopped.

This obviously allows a substantial energy saving in the case of low use of the press 2.

The press 2 thus becomes more versatile, i.e. it can operate with the desired efficiency both in the case of high production rates and in the case of low use.

The central control unit 8 is also adapted to control the inverter of each of the hydraulic power packs 5a,5b,5c,5d so as to adjust the rotation speed of the respective pump, so as to vary the flow of pressurised oil supplied to the presser unit 3, i.e. to the hydraulic cylinder 4.

In particular, the flow rate of pressurised oil fed to the presser unit 3 can be varied very precisely both by acting on the inverter of each of the power packs 5a,5b,5c,5d, and by possibly excluding the operation of one or more of the power packs 5a,5b,5c,5d themselves.

Moreover, this characteristic can make it possible to obtain the best operating conditions of the power packs 5a,5b,5c,5d also in terms of the efficiency of the respective electric motors.

Indeed, for example, in some operating situations it may be advantageous, in terms of energy consumption, to exclude one or more of the power packs 5a,5b,5c,5d to thus allow the electric motors of the power packs still operating to work in maximum efficiency conditions, rather than operate all of the power packs 5a,5b,5c,5d simultaneously with lower speeds of the motors and thus not optimal.

The central control unit 8 is also adapted to simultaneously control the inverters of all of the hydraulic power packs 5a,5b,5c,5d so as to maximise the rotation speed of the respective pumps, so as to consequently maximise the flow rate of pressurised oil fed to the hydraulic cylinder 4.

This operating situation can be particularly advantageous, for example, during the descent of the piston of the hydraulic cylinder 4, to carry out a pressing cycle of products.

Indeed, the descent step of the piston of the hydraulic cylinder 4, i.e. the piston itself approaching the product that must then be pressed, must be carried out in the shortest time possible, to thus minimise the production idle times.

Also object of the present invention is a press 2 for ceramic products, comprising a presser unit 3 provided with at least one hydraulic cylinder 4, and a hydraulic plant 1 for actuating the presser unit 3 having the characteristics described earlier. The invention thus conceived achieves important technical advantages.

Indeed, as stated, the presence in the hydraulic plant 1 of many hydraulic power packs 5a,5b,5c,5d connected in parallel to feed the same presser unit 3 makes it possible to always maintain the operation of the press 2 that incorporates the plant 1 according to the invention, since possible technical interventions on one of the power packs 5a,5b,5c,5d in the case of failure or for maintenance reasons are managed by simply excluding the power pack in question and keeping the press 2 in operation at optimal or at least certainly acceptable operating speeds.

Moreover, the presence in the hydraulic plant 1 of many hydraulic power packs 5a,5b,5c,5d connected in parallel to feed the same presser unit 3 makes it possible to make the operating conditions of the press 2 that incorporates the plant much more versatile and flexible, since the operating parameters of the single power packs 5a,5b,5c,5d can be managed autonomously through the central control unit 8, and also in a coordinated manner to obtain the best performance also and above all in terms of energy saving. The advantages described above are obtained with a much simpler and more cost- effective constructive solution, and one which moreover does not require substantial modifications either to the structure of the press 2 or even less so to the plant engineering part thereof.

5 Indeed, the hydraulic plant 1 according to the present invention can also be installed on pre-existing presses 2 as retrofits, by simply replacing the existing conventional hydraulic power pack with it.

The present invention has been described according to preferred embodiments, but equivalent variants can be conceived without departing from the scope of l o protection offered by the following claims.