System of a pair of forging dies and a device for cleaning the event of a forging die, and method of operating said assembly

Abstract

An aspect of the invention relates to a device (100) for cleaning a vent (20) of a first forging die (11), suitable for receiving, between the first die and a second die, a metal blank to be shaped in order to produce a metal part, the cleaning device comprising: - a pump (110) for injecting an aqueous solution, suitable for injecting the aqueous solution into the vent (20), - an ultrasound generator (150), suitable for generating ultrasound waves within the vent (20), - an air intake (140) suitable for ensuring a venting of the vent (20), and - a valve system (130) for alternately controlling at least the injection of aqueous solution and ultrasound and the venting of the vent (20). Another aspect of the invention relates to a method for using the device.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an assembly of a pair of forging dies and a device for cleaning the vent of a forging die, enabling the removal of residues that cause blockages in the vent. It also relates to a method for implementing this assembly.

[0002] The invention has applications in the field of metal forging and, in particular, in the fields of die forging, stamping or extrusion of metal parts such as parts for aeronautical turbomachinery. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] The manufacture of metal parts by forging consists of shaping a piece of metal, called a blank or blank, using a pair of closed dies pressed together with a compression tool such as a press or hammer. Each die, usually made of metal, has an outer face that comes into contact with the compression tool and an inner face that comes into contact with the metal blank. The inner face of each die in the pair of dies generally bears the impression of the shape chosen for the metal part, the inner faces of the dies in a pair of dies being positioned opposite each other during compression.

[0004] When one die is closed onto another, it frequently happens that, due to the geometries of the inner faces of the dies, air becomes trapped between the metal blank being shaped and one (or even both) inner faces of the dies. Air is largely incompressible, and once the dies are closed, the inter-matrix space is airtight. This creates one or more air pockets between the metal blank and the die(s). The presence of these air pockets radically alters the stresses within the die and the flow of the heated metal blank between the dies, in the vicinity of these pockets, which can lead to several problems.Air pockets can, for example, generate filling problems, which lead to inaccurate geometry of metal parts and therefore scrap, metallurgical risks due, for example, to heating of the metal blank, risks of premature damage to dies or die cavities, etc. All these problems, of course, have consequences on the cost and lead time of manufacture.

[0005] To prevent the formation of these air pockets, it is known to machine one or more vents in at least one of the dies in the die pair. A vent is an opening that passes completely through the die wall to allow the air trapped between the two dies to escape. An example of a die pair with a vent is shown in the diagram. figure 1 In this example, the matrix pair 10 consists of: a first matrix 11, or upper matrix, whose inner face 11a is provided with a first imprint 13, and a second matrix 12, or lower matrix, whose inner face 12a is provided with a second imprint 14.

[0006] In this example, one of the dies, for example the upper die 11, has a vent 20 extending through the entire thickness of said die so as to create an exhaust channel between the inner face 11a and the outer face 11b of the die 11. This vent 20, generally made by drilling, has an air inlet 21 opening onto the inner face 11a of the die 11, preferably at a point where air is trapped on the cavity (for example, a point where the cavity forms an acute angle). The vent 20 also has an air outlet 22 opening onto the outer face 11b of said die 11, which is a free surface without obstruction to airflow.

[0007] To shape the metal blank, the two dies 11 and 12 are assembled and pressed together, for example by means of their side handles 30 or a press or a hammer, etc. The air trapped between the metal blank and the dies 11, 12 at the time of die assembly can flow through the air inlet 21 of the vent 20 to the air outlet 22 of the vent and then escape from the die.

[0008] However, in industry, for productivity reasons, forging is carried out in batches, or series, of several parts (50, 100, 300, etc.) formed one after the other as frequently as possible. During these forging campaigns, the vent tends to become clogged as parts are produced by the accumulation of a mixture of residues from industrial operations and gradually loses its effectiveness. This mixture of residues can consist, depending on the type of forging, of lubrication residues (for example, from graphite or carbon deposits), oxide residues from the oxidation of metallic materials, workshop dust, particles from the wear of the dies, particles from the wear of the metal blank being formed, enamel residues, etc.It has been observed, for example, that a vent with a diameter between 0.2mm and 4mm, whose matrix is ​​used to form by spinning parts in Titanium alloy (for example TA6V) and on which a layer of lubricant (for example an aqueous solution of graphite) is deposited after each forging, becomes blocked from the second or third forged part.

[0009] The fact that the vent gradually becomes clogged during the production run affects the reproducibility of the metal parts, whose shape varies as the run progresses. Indeed, during forging, various residues are carried by the airflow into the vent, where they gradually accumulate. This accumulation alters the pressure drop across the vent and reduces its efficiency. With the air having difficulty escaping, the spread of the metal blank to be shaped is altered, and the shape of the metal part obtained at the end of the forging process is changed. figure 2This schematically represents an example of a vent 20 in which residues 41 have accumulated, forming a blockage that makes airflow difficult or even impossible. This impaired airflow creates an air pocket 42 upstream of the accumulated residues, which induces all the risks and drawbacks already mentioned previously for the case of ventless matrices.

[0010] To prevent the vent from clogging, it is known to increase its diameter, particularly at its inlet on the inner face of the die. A large-diameter vent typically ranges from 2 mm to 25 mm. However, this practice only delays the clogging, which will eventually occur anyway. Furthermore, this practice creates a forged protrusion on the metal part. figure 3This schematically represents an example of a metal part 40 formed from a metal blank in a die 11. This example shows a protrusion 43 formed on the metal part 40 at the opening 21 of the vent 20 by the metal blank cast into the vent on the surface of the mold cavity. Such a protrusion not only results in metal loss, but also causes the part to jam in the cavity, necessitates shearing of the protrusion in the vent, and weakens the die.

[0011] Another common practice to prevent vent clogging is to stop forging between each part production run to remove the residue blockage. This vent cleaning is usually done manually with a brush-type tool. However, such an operation is time-consuming and hazardous to the operator's safety and health. Indeed, forging is generally performed at very high temperatures (the blank temperature is approximately 900°C or higher, and the die temperature is around 300°C) to allow for shaping. Under such conditions, it is therefore difficult for the operator to safely unclog the vent. Furthermore, given its small diameter, the vent is often difficult to locate on a hot, lubricant-coated die, resulting in a relatively lengthy procedure.Furthermore, given the thermal conditions, fumes emanating from the materials and tools can obstruct the operator's visibility, further increasing the intervention time. The productivity of the metal parts is therefore significantly reduced by these cleaning operations.

[0012] There is therefore a real need for forging tooling in which the vents of the forging dies can be cleaned without stopping the production of metal parts and without reducing productivity. SUMMARY OF THE INVENTION

[0013] To address the aforementioned problems of unclogging forging die vents without loss of productivity, the applicant proposes a forging tooling which includes forging dies and a device for cleaning the die vents by injecting an aqueous solution and ultrasound into each vent.

[0014] According to a first aspect, the invention relates to an assembly of a pair of forging dies and a device for cleaning a vent of a first forging die adapted to receive, between said first die and a second die, a billet of metal to be shaped to produce a metal part, said cleaning device being positioned at the outlet of the vent of the first forging die and comprising: an aqueous solution injection pump, adapted to inject aqueous solution into the vent, an ultrasonic generator, adapted to generate ultrasonic waves in the vent, an air intake adapted to ensure venting, and a valve system to alternately control at least the injection of aqueous solution and ultrasound and venting.

[0015] This kit allows for regular and easy cleaning of the matrix vent to remove residues before they accumulate and create a blockage.

[0016] In addition to the characteristics mentioned in the preceding paragraph, the assembly, according to one aspect of the invention, may have one or more complementary characteristics from the following, considered individually or in all technically possible combinations: The vent extends between an inlet opening inside the die and an outlet opening outside the die. The injection pump is installed at the vent outlet to project the aqueous solution from the outlet to the vent inlet. The cleaning device includes a suitable evacuation device to remove residues from the forging of the metal part from the vent. The evacuation of these residues is controlled, after the injection of the aqueous solution and ultrasound, by a valve system. The evacuation device includes an air blower installed at the vent outlet that injects air into the vent from the vent outlet. The evacuation device also includes a suction device installed at the vent outlet that removes the aqueous solution along with the residues.The ultrasonic generator comprises a plurality of ultrasonic transducers mounted axisymmetrically around the vent outlet. The ultrasonic generator also includes an annular ultrasonic transducer, mounted, via a central opening, around the vent outlet. The valve system comprises a first valve connected to the evacuation device, a second valve connected to the injection pump, and a third valve connected to the air intake. The aqueous solution injected by the injection pump contains a corrosion inhibitor. It includes a pressure probe adapted to detect the pressure of the injected aqueous solution, said probe being connected to an automatic processing unit capable of automatically controlling the valve system and the ultrasonic generator.

[0017] Another aspect of the invention relates to a method for cleaning a vent in a forging die, implementing the assembly defined above. This method comprises, at the end of a forging operation on a metal part, the following operations: installation of the cleaning device at the vent outlet of the first forging die, opening of the injection pump and starting of the ultrasonic generator in order to insert aqueous solution and ultrasound into the vent, after loosening and detachment of the residues, closing of the injection pump and the ultrasonic generator and opening of the air intake.

[0018] This process has the advantage of being able to be implemented during an inter-operational period so that it does not generate any loss of time and therefore no decrease in productivity.

[0019] This cleaning process may have one or more of the following complementary characteristics, considered individually or in all technically possible combinations: After closing the injection pump and the ultrasonic generator, the procedure involves opening the evacuation device to remove the aqueous solution and residues. This evacuation device is then closed before the air intake is opened. The opening and closing of the injection pump, the evacuation device, and the air intake are controlled by a valve system in which a first valve controls the evacuation device, a second valve controls the injection pump, and a third valve controls the air intake. This procedure is implemented during an inter-operational period for setting up the materials and tooling necessary for forging the new metal part. It is implemented at the end of each forging operation for a predefined series of metal parts. BRIEF DESCRIPTION OF THE FIGURES

[0020] Other advantages and features of the invention will become apparent from the following description, illustrated by the figures in which: There figure 1 The figure already described represents a schematic cross-sectional view of an example of vented forging dies; figure 2 The diagram, already described, represents a schematic view of a metal part being forged when residues have accumulated in the vent; figure 3 The diagram, already described, represents a schematic view of a metal part being forged when the die vent is of large diameter; figure 4 represents a schematic view of an example of a cleaning device implemented in the invention; The figure 5 schematically represents the cleaning device of the figure 4 during different phases of cleaning; and The figure 6represents, in the form of a functional diagram, the different operations of the process of implementing the cleaning device. figure 4 . DETAILED DESCRIPTION

[0021] An example of a forging tool equipped with a device for cleaning the vent of a forging die, configured to prevent the formation of a blockage in the vent and without affecting the productivity of the metal parts, is described in detail below, with reference to the accompanying drawings. This example illustrates the features and advantages of the invention. It should be noted, however, that the invention is not limited to this example.

[0022] In the figures, identical elements are identified by identical references. For the sake of readability, the size scales between represented elements are not respected.

[0023] An example of a forging tool comprising forging dies and a device for cleaning the vents of these dies according to the invention is schematically represented on the figure 4 , at the output of a forging matrix vent. As described previously, vent 20 can be implemented in the upper or lower matrix. One or more vents can also be implemented in each of the two matrices of the matrix pair. In the example of the figure 4 The vent 20 is made by drilling into the die 11 and extends through the entire thickness of the die, between the inner face 11a and the outer face 11b of said die. Of course, the die may include several vents distributed at different locations within the cavity, each of these vents being cleaned successively or simultaneously by the cleaning device as described below.

[0024] As depicted on the figure 4The vent 20 comprises an air inlet 21 opening onto the inner face 11a of the die 11 and an air outlet 22 opening onto the outer face 11b of said die, also called the external outlet. The vent 20 can have various shapes, such as, for example, a cross-section of various shapes (e.g., circular, square, triangular, etc.) or dimensions (e.g., a diameter ranging from 0.2 to 7 mm at the surface and, preferably, from 0.5 to 5 mm). The vent 20 can also have a cross-section whose shape and dimensions vary along its length between its inlet 21 and its outlet 22.

[0025] The vent 20 cleaning device 100, more simply called the cleaning device, includes an injection pump 110 adapted to inject an aqueous solution into vent 20. The injection pump 110 includes: a receiving pipe 111 of the aqueous solution, connected to a container 113 containing aqueous solution or to a source or any other device for supplying the injection pump 110 with aqueous solution, an ejection pipe 112 of the aqueous solution, connected to the outlet 22 of the vent 20, via a valve system 130 described later, and a set of components ensuring the pressurization of the aqueous solution so that the aqueous solution injected into the outlet of the vent 20 by the ejection pipe 112 is at a pressure greater than the pressure of the aqueous solution in the receiving pipe 111.

[0026] The injection pump 110, of conventional design, has a capacity adapted to the quantity of aqueous solution injectable into vent 20. This aqueous solution may contain, in addition to water, compounds offering various properties advantageous for vent cleaning, such as a solvent or a descaling agent. The choice of detergent may depend, in particular, on the temperature of the billet and / or the matrices, as well as the metallic material of the vent. The aqueous solution may contain, for example, a predefined concentration of a detergent such as glycol, alkaline sodium hydroxide, alcohol, non-ionic surfactants, alkaline surfactants, etc., which, through its surfactant properties, helps to remove residues lodged in the vent. The proportion of detergent in the aqueous solution may vary, for example, between 2 and 10% by mass and, more advantageously, between 4 and 5%.

[0027] In one variation, the aqueous solution may contain a corrosion inhibitor, such as amines, an alkaline solution, ammonia, dechlorinated water, etc., which, when the matrix is ​​metallic, prevents any risk of rust formation inside the vent. This corrosion inhibitor can be mixed with the aqueous solution, preferably alkaline (pH > 7), with or without detergent.

[0028] Regardless of the aqueous solution chosen, it can be injected at ambient temperature, that is, at the temperature of the location, generally a workshop. It can also vary, relative to ambient temperature, from a few degrees Celsius (in winter conditions, for example, taking care not to let the aqueous solution freeze) up to about 60 degrees Celsius (in summer conditions, for example, in a forge workshop with surrounding furnaces). Advantageously, it is possible to thermostat the aqueous solution between 20°C and 60°C and, even more advantageously, between 40°C and 55°C.

[0029] In some embodiments, the aqueous solution can be stirred, continuously or at regular intervals, for example by means of a stirrer, so that the aqueous solution is homogeneous regardless of the compounds and / or agents present in said solution.

[0030] The injection pump 110 can be a conventional pump, sized according to, for example, the pressure drop calculated in the discharge pipe and the vent. Following non-exhaustive examples, the injection pump 110 can be chosen to meet the following properties: Equivalent length of 1m, pressure of 1.001 atmosphere with a flow rate of 10 l / h, filling of vent 20 in less than 20 seconds; or Equivalent length of 1m, pressure of 1.017 atmosphere with a flow rate of 100 l / h, filling of vent in less than 1.5 seconds; or Equivalent length of 1m, pressure of 2.35 atmospheres, with a flow rate of 500 l / h, filling of vent in less than 0.25 seconds; or Equivalent length of 1m, pressure of 2.33 atmospheres with a flow rate of 1000 l / h, filling of vent in less than 0.13 seconds.

[0031] In addition to the injection pump 110, the cleaning unit 100 also includes an ultrasonic generator 150, a drain 120, an air intake 140, and a valve system 130. All of these components can be mounted in a frame, for example, a mobile frame adapted for movement to the die, or a fixed frame mounted on the outer face of the die. Whether mobile or fixed, this cleaning unit is designed to be installed at the vent outlet, i.e., at the external opening of the vent.

[0032] The ultrasonic generator 150 is a device that produces ultrasound waves to remove forging residue from the walls of vent 20. The ultrasonic generator produces ultrasound waves through successive compression and decompression phases. The decompression phases generate a multitude of microscopic bubbles in the aqueous solution. During the compression phase, these bubbles implode, creating turbulence at the vent to be cleaned, which dislodges the residue. The ultrasound waves can be produced, for example, at frequencies between approximately 25 and 90 kHz, particularly between 30 and 60 kHz, and especially between 40 and 50 kHz.

[0033] The ultrasonic generator 150 may include at least two ultrasonic transducers positioned axisymmetrically around the vent outlet 22, for example, fixed to the outer face 11b of the matrix. Alternatively, the ultrasonic generator 150 may include a single annular-type ultrasonic transducer positioned permanently or quasi-permanently around the vent outlet 22, either fixed to the outer face 11b of the matrix or directly fitted around the vent outlet.

[0034] The evacuation device 120 is designed to remove the aqueous solution and residues dislodged by the aqueous solution and the ultrasound from vent 20. This evacuation device 120 includes a discharge pipe 121 connected to the vent outlet 20 via a valve system 130, which will be described later. The evacuation device 120 may include a residue retention tank 122 to collect the residues and the aqueous solution.

[0035] Air intake 140 is an air inlet pipe connected to the outlet of vent 22 and opening to the atmosphere. This air intake 140 ensures that vent 20 is vented to the atmosphere once the aqueous solution containing residue has been removed. This venting allows the vent to dry before a new metal part is forged.

[0036] The valve system 150 comprises several interconnected valves that alternately control the injection of the aqueous solution with ultrasound, the removal of residue, and the venting of the air intake. The valve system 150 includes a first valve V1 connected to the removal device 120, a second valve V2 connected to the injection pump 110, and a third valve V3 connected to the air intake 140.

[0037] The second valve V2 is intended to control the opening or closing of the ejection line 112 connecting the injection pump 110 to the vent 20. In particular, when the second valve V2 is closed, the injection pump 110 does not rotate and when the second valve V2 is open, the injection pump rotates and sends aqueous solution into the vent 20.

[0038] The first valve V1 is intended to control the opening or closing of the evacuation pipe 121 connecting the evacuation device 120 to the vent 20. In particular, when the first valve V1 is closed, the evacuation device does not operate and when the first valve V1 is open, the evacuation device 120 operates and evacuates the aqueous solution with the residues out of the vent 20.

[0039] The third valve V3 is intended to control the opening or closing of the air inlet pipe connecting the air intake to vent 20. When the third valve V3 is closed, no air enters the vent and when the third valve V3 is open, air enters vent 20.

[0040] According to one embodiment, a single pipe is mounted in the outlet of vent 20, this single pipe replacing the ejection pipe 112, the air inlet pipe and the discharge pipe 121 in the portion between the outlet of vent 20 and the valve system 130. This pipe, like all the other pipes of the cleaning device, can be for example a tube, a pipe or any other closed conduit that can be inserted into the outlet of vent 20 or fixed around the outlet of vent 20 to ensure a passage of fluid - aqueous solution and / or air - between said vent and the cleaning device.In the embodiment where a single pipe is connected to the outlet of vent 20, this single pipe is connected to a "pipe node" serving the discharge pipe 121 of the discharge device 120, the air inlet pipe of the air intake 140 and the ejection pipe 112 of the injection pump 110. This embodiment has the advantage of allowing a single connection of the cleaning device to the outlet of vent 20 to carry out all the cleaning operations which will be described later.

[0041] In one variant, the vent outlet 22 is fitted with a sealing gasket 160 that creates a hermetic seal between the pipe—for example, the single pipe or the exhaust pipe—the air intake pipe, or the discharge pipe. This sealing gasket 160 is selected to have properties and stability compatible with the heating temperature of the matrix.

[0042] In some embodiments, the evacuation device 120 comprises only a pipe allowing the residues carried by the aqueous solution to be discharged from the vent. In other embodiments, the evacuation device 120 includes an air blower installed at the outlet of the vent 20, after the first valve V1. This blower is designed to inject an airflow into the vent from its outlet. This blower may include, for example, a blower pump sized using a pressure drop calculation. As non-exhaustive examples, the blower pump may be selected to stabilize in less than 1 second with a holding time of 10 to 20 seconds and to meet the following properties: a minimum blowing pressure of 140 kPa and an air flow rate of 10 l / minutes over a length of 1m; or a minimum blowing pressure of 200 kPa and an air flow rate of 10 l / minutes over a length of 1m; or a minimum blowing pressure of 142 kPa and an air flow rate of 40 l / minutes over a length of 1m.

[0043] In one variant, the aqueous solution injection pump 110 and the blower pump of the evacuation device 120 are a single pump adapted to switch between aqueous solution and air. In this case, valves V1 and V2 can be a single valve offering one closed position and two open positions, one for air and the other for aqueous solution.

[0044] In other embodiments, the cleaning device may include a suction device installed at the outlet of vent 20, after the first valve V1, ensuring suction of the aqueous solution along with the residues. As non-exhaustive examples, the suction device may be chosen to stabilize in less than 1 second with a holding time of 10 to 20 seconds and to meet the following properties: a suction pressure of 40 kPa (vacuum of 110 kPa) and a flow rate of 10 l / minutes over a length of 1m; or a suction pressure of 40 kPa (vacuum of 110 kPa) and a flow rate of 40 l / minutes over a length of 1m.

[0045] Embodiments in which the evacuation device 120 includes an air blowing device or a suction device have the advantage that the vent is dried before being reused for forging a new part. Therefore, it is not necessary to treat the aqueous solution against limescale.

[0046] In some embodiments, the cleaning device can be manually operated by an operator who opens and closes the various valves V1, V2, V3 of the valve system 130 as the cleaning operations progress. The operator also controls the ultrasonic generator using an on / off button. In other embodiments, all the valves of the valve system 130 are connected to an automatic processing unit, such as a computer, which controls the opening and closing of the valves and the activation of the ultrasonic generator according to predetermined timing data. In these embodiments, the operator only initiates the cleaning operations by pressing an on / off button.In other embodiments, a pressure probe is housed, for example, between the injection pump 110 and the air inlet 21, in particular between the second valve V2 and the air inlet 21, preferably close to said second valve V2. This pressure probe, adapted to detect the pressure of the aqueous solution injected into the vent 20, is connected to an automatic processing unit (for example, a computer) which automatically controls the various valves of the valve system 130 and the ultrasonic generator, as soon as a predefined threshold pressure is detected.

[0047] The cleaning device 100, as described above, can be implemented after each forging operation of a metal part, or after a predetermined number of forged metal parts, or whenever the operator deems it necessary. Preferably, it will be implemented regularly during a forging campaign, for example, after the production of 1 to 3 metal parts, to ensure consistent air removal after each forging operation.

[0048] An example of a cleaning operation is shown on the Figures 5 And 6Immediately after a metal part is forged, the cleaning device 100 is activated, either automatically or manually by the operator. The second valve V2 opens, activating the injection pump 110 and the ultrasonic generator 150. A predetermined quantity of aqueous solution is then injected into the vent 20, and ultrasonic waves are pulsed into the aqueous solution inside the vent (phase A of the figure 5The aqueous solution and ultrasonic waves work together to dislodge the blockage or residue lodged in the vent, the accumulation of which could lead to a blockage. Vent 20, filled with pressurized aqueous solution, acts as a wave vector. Within the aqueous solution, the ultrasonic waves trigger successive compression phases, which create small bubbles (cavitation), and decompression phases during which the bubbles implode violently. As the bubbles implode, the residue particles detach and separate from one another. When the aqueous solution contains detergent, the detachment and separation of the residue particles are facilitated and accelerated. The residue dislodgement takes from a few seconds to one minute.

[0049] Once the residues are broken up, under the effect of pressure and ultrasound, part of the aqueous solution and residues are ejected in a micro-jet 115 through the vent inlet 21, at the level of the indentation (phase B of the figure 5 ). The quantity of aqueous solution ejected through inlet 21 is small in proportion to the quantity injected.

[0050] As soon as a micro-jet 115 of aqueous solution emerges from vent 20 through its inlet 21, phase C of the cleaning process is initiated. When the process is operated manually, the operator initiates phase C by closing the second valve V2 and opening the first valve V1 when they observe a micro-jet of aqueous solution. When the process is operated automatically, the drop in pressure in the vent triggers the closing of the second valve V2 and the opening of the first valve V1.

[0051] In embodiments where the exhaust device 120 does not include a blower or suction device, the third valve V3 can be opened quickly after the first valve V1 is opened (phase D) so that air from the air intake 140 can enter the vent 20 and dry it. The third valve V3 can be opened, for example, a few seconds (e.g., about ten seconds) after the first valve V1 has been opened. In embodiments where the exhaust device 120 includes a blower or suction device, the drying of the vent 20 is very rapid and can be completed in about ten seconds.

[0052] As soon as the cleaning operation is complete, the next operation in the forging campaign can begin without delay. In embodiments where the cleaning device is fixed to the die, the third valve V3 remains open during the forging operation. This valve V3 allows air to flow not only from the air inlet 140 to the vent 20, but also from the vent 20 to the air inlet 140. In other words, keeping the third valve V3 open allows the air trapped between the two dies to be vented, via the vent 20, to the outside of the dies and the cleaning device. In embodiments where the cleaning device is mobile, simply moving the cleaning device away from the die opens the vent to the outside again. Thus, during the next forging operation, the air trapped between the dies will be vented directly outside the dies.

[0053] The cleaning operations performed by this cleaning system have the advantage of being able to be carried out relatively quickly, without interrupting the forging process. Indeed, between two forging operations—that is, when a metal part has just been formed and before the next part can be forged—the operator must perform several tasks, such as removing the formed part, placing it in its rack, dusting the die, applying a layer of lubricant to the inside of the die, opening the furnace, taking a billet of metal and placing it in the die, and so on. These various "inter-operation" tasks take a significant and unavoidable amount of time. Since the vent cleaning operations are relatively quick, they can be scheduled during these inter-operation periods so as not to disrupt the duration of a forging process.

[0054] Although described through a number of examples, variants and embodiments, the whole according to the invention includes various variants, modifications and improvements which will be obvious to a person skilled in the art, it being understood that these variants, modifications and improvements form part of the scope of the invention, as defined in the attached claims.

Claims

1. Assembly of a pair of forging dies and a device for cleaning (100) a vent (20) of a first forging die (11) suitable for receiving, between said first die and a second die, a metal blank to be shaped in order to produce a metal part, said device for cleaning being located at an outlet of the vent of the first forging die and comprising: - a pump (110) for injecting an aqueous solution, suitable for injecting the aqueous solution into the vent (20), - an ultrasound generator (150), suitable for generating ultrasound waves within the vent (20), - an air intake (140) suitable for ensuring a venting of the vent (20), and - a valve system (130) for alternately controlling at least the injection of aqueous solution and ultrasound and the venting of the vent (20).

2. Assembly according to claim 1, characterised in that, the vent (20) extending between an inlet (21) opening inside the die and an outlet (22) opening outside the die, the injection pump (110) is installed at the outlet (22) of the vent to spray the aqueous solution from the outlet to the inlet (21) of said vent.

3. Assembly according to claim 1 or 2, characterised in that it comprises an evacuation device (120) suitable for evacuating, outside the vent, residues coming from the forging of the metal part, the evacuation of the residues being controlled, after the injection of aqueous solutions and ultrasound, by the valve system.

4. Assembly according to claim 3, characterised in that the evacuation device (120) comprises an air blowing device installed at the outlet of the vent and ensuring an injection of air inside the vent from the outlet (22) of said vent.

5. Assembly according to claim 3, characterised in that the evacuation device (120) comprises a suction device installed at the outlet (22) of the vent and ensuring a suction of the aqueous solution with the residues.

6. Assembly according to any of claims 1 to 5, characterised in that the ultrasound generator (150) comprises a plurality of ultrasound transducers mounted axisymmetrically around the outlet of the vent.

7. Assembly according to any of claims 1 to 5, characterised in that the ultrasound generator (150) comprises an annular ultrasound transducer, mounted, via a central opening, around the outlet of the vent.

8. Assembly according to any of claims 3 to 6, characterised in that the valve system (130) comprises a first valve (V1) connected to the evacuation device, a second valve (V2) connected to the injection pump and a third valve (V3) connected to the air intake.

9. Assembly according to any of claims 1 to 8, characterised in that the aqueous solution injected by the injection pump comprises a corrosion inhibitor.

10. Assembly according to any of claims 1 to 9, characterised in that it comprises a pressure probe suitable for detecting the pressure of the injected aqueous solution, said probe being connected to an automatic processing system able to automatically control the valve system and the ultrasound generator.

11. Method for cleaning a vent of a forging die implementing the assembly according to any of claims 1 to 10, characterised in that, at the end of an operation of forging a metal part, it comprises the following operations: - installation of the device for cleaning at an outlet of the vent of the first forging die, - opening of the injection pump and starting of the ultrasound generator (phase A) so as to insert aqueous solution and ultrasound into the vent, - after separating and detaching of the residues (phase B), closing of the injection pump and of the ultrasound generator and opening of the air intake (phase D).

12. Method for cleaning according to claim 11, characterised in that it comprises, after closing of the injection pump and of the ultrasound generator, an operation of opening the evacuation device (phase C) in order to evacuate the aqueous solution and the residues, said evacuation device being closed again before the opening of the air intake.

13. Method for cleaning according to claim 12, characterised in that the opening / closing of the injection pump, the opening / closing of the evacuation device and the opening / closing of the air intake are controlled from a valve system (130) wherein a first valve (V1) controls the evacuation device, a second valve (V2) controls the injection pump and a third valve (V3) controls the air intake.

14. Method for cleaning according to any of claims 11 to 13, characterised in that it is implemented during an inter-operation period of setting up the materials and tools required for the forging of the new metal part.

15. Method for cleaning according to any of claims 11 to 14, characterised in that it is implemented at the end of each forging operation of a predefined series of metal parts.

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