EP3200940B1

EP3200940B1 - Press for the hot moulding of pieces

Info

Publication number: EP3200940B1
Application number: EP15841068.8A
Authority: EP
Inventors: Francesco Meschini
Original assignee: Hydromec SRL
Current assignee: Hydromec SRL
Priority date: 2014-09-30
Filing date: 2015-09-08
Publication date: 2018-11-28
Anticipated expiration: 2035-09-08
Also published as: TR201902772T4; EP3200940A2; WO2016051299A3; ES2713224T3; WO2016051299A2

Description

This invention relates to a mechanical press for the hot moulding of pieces, in particular hollow pieces in brass or aluminium.
These presses usually comprise a fixed structure with a vertical axis, anchored to foundations and supporting, in an intermediate part of its height, a horizontal reaction plate. On this structure, is mounted a slide that is movable vertically with respect to the structure itself and to the reaction plate by means of a control unit so as to cause the opening and closing of the press during its use.
In one of its upper part, the slide supports an upper mould-holder suitable to receive an upper half-shell facing downward and opposite to a complementary lower half-shell. This lower half-shell is, in turn, applied on a lower mould-holder and movable in height above the reaction plate.
The lower mould-holder rests, by means of small columns that pass through the reaction plate, on a floating cushion provided under the reaction plate and suitable to control the movements in height of the lower mould-holder following the closure of the press, in order to ensure the proper reaction to the opening force of the half-shells during pressing.
So, in this type of mechanical presses, to increase the reaction to the opening of the mould, it is necessary to increase the force exerted by the floating cushion. However, this results in an increase in the twisting moment that is discharged on the mechanical members of the press that transmit the pressing force. So, to ensure the integrity of the mechanical members of the press, the reaction force cannot be increased beyond a certain value and this constitutes a limitation of the performance of the press.
The purpose of this invention is to provide a mechanical press, in particular for the hot forging of hollow pieces, able to overcome such limit of the known presses.
This purpose is achieved with a press according to claim 1. The dependent claims describe preferred embodiments of the invention.
The characteristics and advantages of the press according to the invention will, in any case, be evident from the following description of its preferred embodiments, provided by way of non-limiting example, with reference to the accompanying figures, wherein:

Figures 1-4 schematically illustrate the press according to the invention, in axial section and in as many steps of a pressing operation;
Figure 5 is a diagrammatic cross section of the press that shows the positioning of the floating cushion and the reaction cylinders;
Figure 6 is a diagram of the hydraulic pressurisation circuit of the floating cushion and the reaction cylinders; and
Figures 7 and 7a show a diagram of the forces of the press in the moment of closing of the mould, in a press according to the known technique and in a press according to the invention.

Said drawings of a press 1 for the hot moulding of pieces, in particular hollow pieces made of brass or aluminium, schematically represent the functional elements that contribute to a preferred embodiment of this invention.
The press 1 comprises a fixed structure 10 with a vertical axis X, anchored to foundations and supporting, in an intermediate part of its height, a horizontal reaction plate 12. On this structure, is mounted a slide 14 that is movable vertically with respect to the structure itself and to the reaction plate 12 by means of a control unit - not shown - so as to cause the opening and closing of the press during its use.
The slide 14 supports an upper mould-holder 16 suitable to receive an upper half-shell 18. This upper half-shell 18 is facing downward and opposite to a lower half-shell 20, complementary to the upper half-shell 18 and defining with this a cavity adapted to receive a semi-finished piece to be forged.
This lower half-shell 18 is, in turn, applied on a lower mould-holder 22 and movable in height above the reaction plate 12.
The lower mould-holder 22 rests, for example by means of columns 24 that pass through the reaction plate 12, on a floating hydraulic cushion 30 provided under the reaction plate 12 and suitable to control the movements in height of the lower mould-holder 22 following the closure of the press, in order to ensure the proper reaction to the opening force of the half-shells during pressing.
To this end, the floating hydraulic cushion 30 is connected to a hydraulic pressurisation circuit 50 so as to exert a progressive cushion reaction force opposing the opening of the half-shells when the floating cushion 30 is subjected to compression.
In other words, the floating hydraulic cushion 30 is substantially constituted by a hydraulic cylinder comprising a piston 32 to which is operatively connected the lower mould-holder 22 and that is slidable with respect a fixed cylindrical body 34 that defines a cylinder chamber 36 containing the oil under pressure that controls the movement of the piston 32 of the floating cushion 30.
Therefore, the assembly of the floating cushion 30 and the hydraulic pressurisation circuit 50 forms a hydraulic spring that, by contrasting with a progressively increasing force the lowering of the lower mould-holder 22, opposes the opening of the mould during pressing.
The slide 14 is movable vertically with respect to the reaction plate 12 between an upper end-stroke position, in which the upper half-shell 18 is distant from the lower half-shell 20, and a lower end-stroke position, in which the upper half-shell 18 is placed in contact with the lower half-shell 20 and the floating cushion 30 is stressed so as to exert a maximum cushion reaction force.
As will be better described below, when the operation of the press is described, during its descending movement, the slide 14 passes through an intermediate position, in which the upper half-shell 18 is placed in contact with the lower half-shell 20 and the floating cushion 30 is stressed so as to exert a minimum cushion reaction force.
In other words, when the slide 14 is in the lower end-stroke position, the piston 32 of the floating cushion 30 is completely, or almost completely, retracted in the chamber 36 of the cylindrical body 34, so as to compress to the maximum the oil contained in pressurisation circuit 50. While, when the slide 14 is in the intermediate position, the upper half-shell 18 is placed in contact with the lower half-shell 20, but the floating piston 32 of the floating cushion 30 is in an extracted position from the cylindrical body 34, which corresponds to the minimum compression of the oil of the pressurisation circuit 50.
As said, the cushion reaction force increases progressively as the slide 14 approaches the lower end-stroke position.
According to an aspect of the invention, the press 1 also comprises a plurality of reaction cylinders 40 connected to a hydraulic pressurisation circuit 50, for example the same hydraulic pressurisation circuit to which the floating cushion 30 is connected. Such reaction cylinders 40 are operatively interposed between the lower mould-holder 22 and the reaction plate 12 and are suitable to exert a progressive cylinder reaction force FCC that opposes the opening of the half- shells 18,20 when the slide 14 exceeds the intermediate position. The floating cushion 30 and the reaction cylinders 40 are arranged in such a way that, when the slide 14 exceeds the intermediate position, the overall reaction force FR at the opening of the half-shells is given by the sum of the progressive cushion reaction force FC with the progressive cylinder reaction force FCC.
For example, the reaction cylinders 40 are mounted on the reaction plate 12 and are suitable to interact, for example with a head 42' of the respective pistons 42, with respective piston abutment seats 44 formed on the lower side of the lower mould-holder 22.
In a preferred embodiment, when the slide 14 is in the lower end-stroke position, the lower mould-holder 22 is in mechanical abutment against the reaction plate 12. To this end, the sides facing the lower mould-holder 22 and the reaction plate 12 are provided with hardened plates 22',12' suitable to withstand the impact of the lower mould-holder 22 against the reaction plate 12.
In a preferred embodiment, when the slide 14 is in the lower end-stroke position, the pistons 42 of the reaction cylinders 40 and the piston 32 of the floating cushion 30 are in a retracted position in which they are not in contact with the respective mechanical lower end-stroke abutments. In this way, the floating cushion 30 and the reaction cylinders 40 do not take the risk of being damaged in the impact between the lower mould-holder 22 and the reaction plate 12.
In a preferred embodiment, on the lower mould-holder 22 are mounted cars 60 bearing respective piece drilling pins 62. These cars 60, with the respective piece drilling pins 62, are movable towards and away from the piece to be moulded in accordance with the movement of the slide 14.
For example, the cars 60 are connected to the lower mould-holder 22 and the fixed structure 10 by means of a lever system - not shown - in such a way that these cars 60 begin to move towards the vertical axis X of the press when the upper half-shell 18 is placed in contact with the lower half-shell 20 during the descending movement of the slide 14. The number and arrangement of the cars 60 and the respective piece drilling piece 62 may vary depending on the number and placement of holes to be made in the piece to be moulded.
In a preferred embodiment, the position of the reaction cylinders 40 on the reaction plate 12 is chosen depending on the position of the cars 60 on the lower mould-holder 22. For example, since there are usually four cars 60 arranged in a cross around the lower half-shell 20 (not necessarily all provided with piece drilling points 62, depending on the number of holes to be made), on the reaction plate 12 are mounted one or two reaction cylinders 40 in correspondence, i.e., below, each car 60.
Figure 5 shows a positioning example of four pairs of reaction cylinders 40 on the reaction plate 12.
In a preferred embodiment, at least some of the reaction cylinders 40 can be powered by the hydraulic pressurisation circuit 50 independently of others of said reaction cylinders. One such independent management of all or some of the reaction cylinders, for example in pairs, allows recovering any play or imbalances of the lower mould-holder 22, in particular in the case in which the mould does not require the activation of all the drilling pins 62 and/or the arrangement of the cars 60, and thus of the related pins 62 is not symmetrical with respect to the vertical axis X of the press.
Furthermore, in a preferred embodiment, the head 42' of the piston 42 of the reaction cylinders 40 has a spherical contact surface with the respective seat 44 in the lower mould-holder 22, so as to compensate for any misalignment between the lower mould-holder 22 and the reaction plate 12.
Figure 6 shows the diagram of a hydraulic pressurisation circuit 50 to which are connected the floating cushion 30 and the reaction cylinders 40.
In a preferred embodiment, the floating cushion 30 and the reaction cylinders 40 are fluidically connected to respective accumulators 52 so as to form as many closed circuits. Each of said closed circuits is controlled by a respective hydraulic control circuit 54, comprising valves, solenoid valves and discharge tanks, suitable in particular for controlling the activation and deactivation of the respective accumulator 52 into and from the respective closed pressurisation circuit, for example as a function of how many, and which, reaction cylinders 40 it is necessary to activate. Each accumulator 52 is loaded by a motor pump 56.
In particular, for each accumulator 52 are defined a minimum pre-load pressure, a load pressure, which determines the reaction force of the floating cushion when the slide reaches the intermediate position, and the reaction force of the reaction cylinders at the moment of their activation, and a maximum pressure, which is reached when the slide has reached the lower end-stroke position and which is a function of the piston stroke of the floating cushion and the stroke of the pistons of the reaction cylinders.
In an embodiment schematically illustrated in Figure 6, the floating cushion 30 is provided with an upper pressurisation chamber and a lower braking chamber, each connected to a respective closed circuit.
We will now describe, with reference to Figures 1-4, a moulding cycle of the press.
Where:

FR,i is the force that opposes the opening of the half-shells at a given instant;
FC,i is the cushion reaction force at a given instant;
FC,min is the minimum cushion reaction force;
FC,MAX is the maximum cushion reaction force;
FCC,i is the cylinder reaction force at a given instant;
FCC,min is the minimum cylinder reaction force;
FCC,MAX is the maximum cylinder reaction force;
FP the nominal force of the press.

In Figure 1, the press is in a start of cycle configuration, in which the slide is in the upper end-stroke position. The floating cushion 30 and the reaction cylinders 40 are not stressed and are in a position of maximum extraction.
In Figure 2, the press is represented with the slide 14 in an intermediate position, in which the upper half-shell 18 is in contact with the lower half-shell 20 and the floating cushion 30 begins to be stressed. The lower mould-holder 22 is barely in contact with the pistons of the reaction cylinders, but does not exert any pressure, or an irrelevant pressure, on them. In this instant, the reaction force when the half-shells are opened is only that exerted by the floating cushion and is the minimum, namely: $FR,1 = FC, \min$
As the slide 14 approaches the lower end-stroke position, the floating cushion is pushed downwards and its reaction force increases, as this is connected to the hydraulic pressurisation circuit, which is pressurised progressively more and more. From a certain moment onwards, also the reaction cylinders contribute to the overall reaction. In this situation, the reaction force at the opening of the half-shells, opposed by the cushion and the reaction cylinders, is: $FR,2 = FC,2 + FCC, \min$
As the slide continues its stroke towards the lower end-stroke position, the reaction force at the opening of the half-shells continues to increase until the optimum value, which is achieved when the lower mould-holder 22 is at a minimum distance, for example 5 mm, from the mechanical abutment with the reaction plate 12 (Figure 3). In this situation, the reaction force at the opening of the half-shells, opposed by the reaction cylinders, reaches the maximum nominal value and is: $FR, 3 = FC,3 + FCC,3$
If, for specific process reasons, one wants to take advantage of the mechanical abutment between the lower mould-holder 22 and the reaction plate 12, the slide is allowed to continue its stroke up until it goes into mechanical abutment against the reaction plate. In this case, therefore, the lower end-stroke position corresponds to the position in which there is a mechanical abutment between the lower mould-holder 22 and the reaction plate 12, and the overall reaction force at the opening of the half-shells is the sum of the maximum cushion reaction force, the maximum reaction cylinder reaction force and the nominal force of the press itself (Figure 4): $FR,4 = FC, MAX + FCC, MAX + FP$
In this situation, an overload device mounted in the slide and suitably calibrated, ensures that the moulding operation does not damage the press itself.
The press according to the invention allows obtaining a high closing force of the half-shells without consequences for the integrity of the mechanical members of the press. It should be noted, in particular, that the reaction cylinders begin to react when the crank angle is very small. In this way the twisting moment turns out to be modest because, although the force increases, the arm is very small.
This innovative aspect of the press according to the invention is illustrated, in particular, in Figures 7 and 7a, which show the force diagram of the press when the slide 14 has exceeded the intermediate position, in the case of the press according to the prior art (Figure 7) and in the press according to the invention (Figure 7a).
In these drawings, the slide 14 is shown connected to the crank mechanism 70 that controls its descending and ascending movements along the press axis X. The force exerted by the press when the slide 14 has passed the intermediate position is the same in the two cases (Fp1 = Fp2). In the press according to the known technique, the reaction force at the opening of the half-shells is given only by the reaction force of the floating cushion: FC1 = Fp1. In the press according to the invention, the reaction force at the opening of the half-shells is given by the sum of the reaction force of the floating cushion with the reaction force of the reaction cylinders: FC2 + FCC2 = Fp2.
So, at equal press force, the reaction force of the floating cushion is smaller in the case of the press according to the invention. This translates into a smaller maximum pressure required for the pressurisation fluid of the cushion in the case of the press according to the invention, and, since this maximum pressure depends on the stroke of the cushion piston, in a stroke C2 < C1.
Such a smaller stroke required from the piston of the floating cushion allows the slide to reach the intermediate position, in which it begins to engage the floating cushion, at a lower height than in the case of the press according to the known technique. This translates into an arm b2 of the crank smaller than the corresponding arm b1 of the known press and, therefore, in a twisting moment Mt2 <Mt1.
To the forms of embodiment of the press according to the invention, a technician in the field, to satisfy contingent requirements, may make modifications, adaptations and replacements of members with others functionally equivalent, without departing from the scope of the following claims.

Claims

Press for the hot moulding of pieces, in particular hollow pieces in brass or aluminium, comprising:
- a fixed structure (10) defining a reaction plate (12);

- an-upper mould-holder(16), suitable to receive an upper half-shell (18);

- a lower mould-holder (22), suitable to receive a lower half-shell (20);

- a floating cushion (30) to which the lower mould-holder (22) is operatively connected, the floating cushion being connected to a hydraulic pressurisation circuit (50) so as to exert a progressive cushion reaction force opposing the opening of the half-shells (18, 20) when the floating cushion is subjected to compression;

- a movable slide (14) to which the upper mould-holder (16) is attached, the movable slide being movable vertically in relation to the reaction plate between an upper end-stroke position, in which the upper half-shell is distant from the lower mould, and a lower end-stroke position, in which the upper half-shell is put together the lower half-shell and the floating cushion is stressed so as to exert a maximum cushion reaction force passing through an intermediate position, in which the upper half-shell is placed in contact with the lower half-shell and the floating cushion is stressed so as to exert a minimum cushion reaction force;
wherein said cushion reaction force increases progressively as the slide approaches the lower end-stroke position;
the press being characterised in that it further comprises a plurality of reaction cylinders (40) connected to a hydraulic pressurisation circuit (50), said reaction cylinders being operatively interposed between the lower mould-holder (22) and the reaction plate (32) and being suitable to exert a progressive cylinder reaction force which opposes the opening of the half-shells when the slide exceeds said intermediate position, the floating cushion and the reaction cylinders being arranged in such a way that, when the slide passes the intermediate position, the overall reaction force to the opening of the half-shells is given by the sum of the progressive cushion reaction force with the progressive cylinder reaction force.
Press according to claim 1, wherein, when the slide is in the lower end-stroke position, the lower mould-holder (22) is in abutment against the reaction plate (12).
Press according to claim 2, wherein, when the slide is in the lower end-stroke position, the cylinder pistons (42) of the reaction cylinders (40) and the cushion piston (32) of the floating cushion (30) are in a rearward position in which they are not in contact with the respective mechanical lower end-stroke abutments.
Press according to any of the previous claims, wherein cars (60) are mounted on the lower mould-holder (22) bearing respective piece drilling pins (62), said cars being movable towards and away from the piece to be moulded according to the movement of the slide (14).
Press according to the previous claim, wherein the reaction cylinders (40) are positioned under and at the respective cars (60).
Press according to any of the previous claims, wherein at least some of the reaction cylinders (40) are powered by the hydraulic pressurisation circuit (50) independently of the other reaction cylinders.
Press according to any of the previous claims, wherein the reaction cylinders (40) have a spherical contact surface (42') with the lower mould-holder (22).