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Title:
METHOD FOR THE ACTUATION OF MECHANICAL MOULDING PRESSES
Document Type and Number:
WIPO Patent Application WO/2021/009578
Kind Code:
A1
Abstract:
Method for the actuation of mechanical moulding presses with a movable upper operating slide and a fixed lower press plane respectively carrying the mould and counter-mould, wherein one or more clutches are provided which intervene during a moulding operating cycle in a respective coupling point of a kinematic mechanism which transforms a rotary drive motion into an alternating linear motion of the operating slide. According to this method, a first coupling point is set for said clutch(es); during a first stroke of a complete moulding step, a verification is effected for controlling whether at said first coupling point there is a request for an actual moulding torque or not; if a torque request is present, there is a signalling of its presence and of a specific area in which this torque request has occurred, stopping the press; a second coupling point is then set, before the first coupling point, when the mould of the upper slide is further away from the lower press plane; the movement of the slide is then restarted and verification continues, allowing the implementation of the complete moulding process when there is an absence of torque at the last coupling point set.

Inventors:
GALLI LORENZO (IT)
Application Number:
PCT/IB2020/055407
Publication Date:
January 21, 2021
Filing Date:
June 09, 2020
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
I M V PRESSE S R L (IT)
International Classes:
B30B15/14; B30B15/12; B30B15/28
Foreign References:
US2781883A1957-02-19
US20090217724A12009-09-03
DE2924078A11980-02-28
Attorney, Agent or Firm:
MARTEGANI, Franco et al. (IT)
Download PDF:
Claims:
CLAIMS

1. A method for the actuation of mechanical moulding presses which are provided with a movable upper operating slide and a fixed lower press plane which respectively carry the mould and counter-mould, wherein one or more clutches are provided which intervene during a moulding operating cycle in a respective coupling point of a kinematic mechanism which transforms a rotary drive motion into an alternating linear motion of the operating slide,

said method being characterized in that:

- a first coupling point is set for said one or more clutches;

- at the start of the movement of the slide, during a first stroke of a complete moulding step, a verification is effected for controlling whether in said first coupling point of said one or more clutches there is a request for an actual moulding torque or not;

- if a torque request is present, there is a signalling of its presence and a specific area in which this torque request has occurred, stopping the press;

- a second coupling point is then set, setting it before the first coupling point, when the mould of the upper slide is further away with respect to the lower press plane and taking into account the specific area signalled for the first coupling point ;

- the movement of the slide is restarted, effecting a further verification such as that previously described; - the complete moulding process can be carried out when said last verification effected results in the absence of torque in correspondence with a last coupling point set;

wherein, in said method, a verification is effected of the absence of torque in the coupling point at each stroke of the press and/or a measuring of the requested torque in the coupling point and a comparison of the measured torque with a pre-set value (Y) grater then zero is carried out, and/or a measuring of the requested torque in each point of the cycle is carried out in order to control the correct implementation of the complete moulding step, stopping the moulding in the presence of torque in said last coupling point set to actuate the moulding operation.

2. The method according to claim 1, characterized in that said moulding torque request is detected in said coupling point by means of extensometer sensors applied to a press mechanism.

3. The method according to claim 1, characterized in that said moulding torque request is detected in said coupling point by means of pressure sensors which detect in real time an increase or a decrease in pressure in hydraulic cylinders positioned between said slide and said kinematic mechanism of the press.

4. The method according to claim 1, characterized in that said moulding torque request is detected in said coupling point by measuring a torque required for a motor element of the press . 5. The method according to claim 1, characterized in that said moulding torque request is detected in said coupling point according to a cycle previously programmed and memorized with a code combined with a mould.

6. The method according to claim 1, characterized in that said coupling point programmed by an operator refers to degrees of an angle around an eccentric.

7. The method according to claim 1, characterized in that said coupling point programmed by an operator refers to a distance with respect to a "top dead centre" (TDC) or a "bottom dead centre" (BDC) of an eccentric shaft of the press.

Description:
METHOD FOR THE ACTUATION OF MECHANICAL MOULDING PRESSES

The present invention relates to a method for actuating mechanical moulding presses.

In the field of moulding, mechanical presses are normally used which have a common general concept. These mechanical presses in fact essentially provide a flywheel, a clutch, a transmission and a connecting rod-crank or lever kinematic mechanism which transforms the motion from rotary to alternating by moving an operating slide.

Some of these presses are designed with large servomotors with a considerable torque in place of the flywheel actuated by the traditional motor. These presses generally have no need for a clutch as there is no moving part to be engaged or connected "speedily" to a part that must take motion.

Some presses are designed with one or more clutches that can alternate or be added in order to connect the kinematic mechanism to different transmissions with different speeds or forces. In these cases the clutch engagement is not only effected at the beginning of the cycle, but can also take place during the cycle.

In this respect, the traditional cycle normally begins with the operating slide positioned at the maximum opening point which is called the "top dead centre" (T.D.C.) .

On effecting a turn of the eccentric shaft, the slide of the press descends to the minimum closing point called "bottom dead centre" (B.D.C.) and then returns to the starting point.

The traditional cycle can stop and then start again, or continue for a desired number of cycles. In particular, it should be remembered that the T.D.C. corresponds to a phase in which the moulds applied to the press are open and therefore there is no torque request. Otherwise, the B.D.C. and the part of the cycle closest to it during the closing of the mould is the phase in which torque is required for obtaining the force for the moulding.

The presence of at least one clutch in the press causes a series of problems. Although the clutch, in fact, can be provided with all the best expedients for accelerating the coupling and dissipating the heat, it still requires a certain coupling time. It is specifically this coupling that creates a frictional slip phase between the parts that are engaged, called "defrictioning" . In particular, this occurs between the rotating part and the stationary part, so that the latter can be put into rotation and so that a coupling can be reached between the two parts capable of transmitting the torque for which the clutch was created. Needless to say, if the coupling occurs when the torque required is minimal there are no problems, but if the coupling takes place when the torque required is significant (even if less than the nominal torque) , this can cause a longer "defrictioning" : and with it, more heat is generated and causing a premature wear of the clutch pads. In general, therefore, in order to mitigate these problems, in a traditional press the clutch is therefore engaged near the T.D.C. In this point, in fact, the torque required is minimal, whereas the maximum torque is required near the B.D.C., when the clutch is already fully engaged and there is no more defrictioning .

In the field of moulding, however, there are presses in which the coupling of the single clutch or other clutches can also take place during phases of the cycle other than the classical T.D.C. And this coupling is programmed by the operator in order to obtain different speeds or torques in different phases of the moulding cycle itself.

In these cases, it is possible that the coupling of the clutch (or even its release) be requested in phases of the cycle where there is a torque request for various reasons

(moulds already joined or closed, material already in the deformation phase, etc.) . And therefore the programming of the coupling point is given by the user' s discretion and experience of the press.

It should be further pointed out that an incorrect manoeuvre at the clutch insertion point causes, as a natural consequence, damage to the clutch.

It should be noted, however, that there are also presses in which there is the presence of one or more clutches with insertion of the same during the operating cycle. Some examples are provided for a better understanding.

In a first example there can be a press provided with two different transmissions with two different gear ratios that take movement from the same or from different flywheels or motors. The two transmissions can be connected via clutches to the same shaft of the kinematic mechanism, thus obtaining two different speeds alternating them in the same cycle, and in this case there are two clutches.

In a further example, there can be a press provided with a primary transmission that takes movement from the flywheel and engages via the clutch with the shaft of the kinematic mechanism, which is also connected to a second transmission provided with a servomotor. Whereas the secondary transmission is programmable and can accelerate or slow down at will, the primary transmission has an almost constant speed determined by the rotation of the flywheel. The coupling of the clutch causes the rotation of the kinematic mechanism shaft to take speed and torque from the flywheel, whereas when disengaged, the shaft of the kinematic mechanism takes speed and torque from the secondary transmission.

The above-mentioned application examples therefore propose presses wherein the rotation of the kinematic mechanism is not constant during the whole cycle as in a traditional press, but can be broken down into different parts with different speeds. The effect is that the operating slide of the press can slow down or accelerate its motion (compared to the classical connecting rod-crank sinusoid) according to the different requirements of the user.

Considering the need for slowing down the cycle during the opening and j uxtapositioning of the mould as secondary, to allow any possible robots to have more time available for loading the material and unloading or moving the piece, in order to increase productivity and therefore decrease specific product costs, most users will try to optimize the press cycle by setting the speed during the deformation phase of the material to the maximum value allowed, beyond which the deformation has an unacceptable quality drop, and then accelerating the speed as much as possible during the opening and j uxtapositioning of the space to save time.

Consequently, as the total cycle time is a sum of times, the lower the slow phase, the higher the productivity will be. For this reason, the user will try to bring the speed change points (and therefore clutch engagement) as close as possible to the starting point of the deformation. The same applies to the speed change point at the end of the deformation and therefore when the slide is opened.

It is therefore evident that if the coupling takes place when the required torque is considerable, an equally significant "defrictioning" occurs, with the generation of greater heat, and there is therefore premature wear of the pads of one or more of the clutches.

The general objective of the present invention is to provide a method in which it is possible to solve the problems and drawbacks mentioned relating to the prior art in an extremely simple, economic and particularly functional way.

A further objective of the present invention is to provide a method which is applicable in all mechanical presses equipped with one or more clutches that are engaged during the moulding operating cycle.

Another objective of the present invention is to provide a method which allows the press clutch (s) to be preserved from premature wear mainly due to the frictioning of the parts that engage during functioning.

The above-mentioned objectives are achieved by a method implemented according to independent claim 1 and the following subordinate claims.

The structural and functional characteristics of the present invention and its advantages with respect to the known art will be even more evident from the following description.

The present invention therefore relates to a method for the actuation of mechanical moulding presses which, composed as specified in the previous introductory part, are essentially provided with a movable upper operating slide and a fixed lower press plane which respectively carry the mould and the counter- mould. In particular, in these mechanical presses one or more clutches can be provided which intervene during a moulding work cycle in a respective coupling point of at least one kinematic mechanism which transforms a rotary control motion into an alternating linear motion of the operating slide.

The present invention proposes a solution to the problem described above by using a method whereby the insertion of the clutch is avoided in the operating phase in which torque is required .

Therefore, in short, for the implementation of this method, the operator in charge of the press programs the press cycle according to his requirements and the clutch coupling point is established on the basis of the cycle programmed.

An electronic control then verifies whether there is torque request in the above coupling point or not.

And at this point there is a double possibility.

If torque is requested, in fact, the electronic control warns the operator to modify the programmed cycle, to change the clutch coupling point. If there is no torque request, the press control allows the implementation of the cycle.

More specifically, what has just been summarized as an example is implemented as follows.

The operator sets a first coupling point for said one or more clutches present in the press and controlled by an electronic control. Subsequently, at the start of the movement of the slide, during a first stroke of a complete moulding step, a verification is effected for controlling whether said one or more clutches are coupled in said first coupling point of said moulding step in which there is no actual moulding torque request .

According to the first hypothesis indicated above, if there is a torque request at the coupling point, then there is a signalling of its presence and a specific area in which said torque request has occurred, stopping the press in order to carry out the necessary correction.

The operator therefore proceeds to set a second coupling point, setting it previous to the first coupling point. And this occurs when the mould of the upper slide is further away from the lower press plane and above all taking into account the specific area in which this torque request occurred, signalled for the first coupling point.

For this setting, the software, having detected it during the previous cycle, indicates in which area of the cycle the torque was detected, thus giving the operator or the software indications as to the area in which the coupling point can be set .

It is only at this point that the operator repeats the start-up of the movement of the slide by carrying out a further verification as previously effected. Consequently, in a positive case, the operator allows the complete moulding process to be implemented when said last verification proves to be without torque in correspondence with a last coupling point set .

Once the operating step according to the method of the present invention has been started, it should be considered that the same method proceeds with a verification of the absence of torque at the coupling point set at each press stroke in order to control the correct implementation of the complete moulding step. If a certain torque results from the verification, this is an indication of some operational or functional problem. Therefore, according to the method, the moulding is stopped as there is torque even if it should operate with a coupling point set without torque from the previous verifications that had given a positive result and allowed the continuation of the moulding step.

It should be pointed out that this method is valid regardless of the detection mode of the need for torque, the data acquisition mode and the processing and consequent action mode used.

Some embodiment examples of the steps of the above method in the presence of different modes are provided hereunder for a better understanding.

First of all, some examples are proposed for detecting the clutch coupling point programmed. In a first, non-limiting example, the electronic system or control directly detects the coupling point from the cycle programmed by the operator, whether it be written in degrees referring to the angle of rotation of the eccentric or in distance from the reference point (B.D.C. or T.D.C.) .

In a second example, the electronic system can detect the coupling point from a cycle previously programmed and stored with a code associated for example with a mould or product.

Examples of detection of the need for torque are also proposed by way of example.

It should be specified that the presence of strain is translated into the need for torque to be able to support it. The method object of the patent application does not necessarily need to measure the amount of torque required, it is sufficient to know whether or not there is need for torque.

The possibility of measuring or determining with more or less precision the torque required is a further "fine tuning" of the system which can improve its functionality, but which does not modify the method of use.

In a first example, detection can take place through extensometer sensors or extensometers applied to the press mechanics. In this way, an elongation or compression is detected and by means of mathematical formulae or amplifiers, the request for strain from the press can be determined in real time. The quantity can also be measured through suitable calculations. The extensometers can be applied to operate with "extension" by detecting the elongation (for example of the structure or a tie-rod of the press), or "compression", detecting the shortening or crushing (for example of a lever or connecting rod or of a block positioned between the thrust point and the reaction point) .

In a second example, the detection is effected through pressure sensors that can detect in real time the increase or decrease in pressure in hydraulic cylinders normally positioned between the slide and the kinematic mechanisms of the press.

Also in this case, by measuring the pressure, the presence or absence of strain is detected and the quantity can be measured by means of appropriate calculations.

In a third example, the detection is effected by measuring the torque required by the motor, whether it be detected directly or indirectly by its electronic drive, or by energy consumption or by the extension of the transmission belts.

It can thus be seen from these examples that the factor common to the detection modes is the combination of the torque- requirement data with a specific moment of time which corresponds to or which can be in the immediate vicinity of the clutch coupling point required by the cycle. This combination can be carried out with mathematical formulae using directly or indirectly the degrees of the rotation angle of the press kinematics, or the time, or a specific position sensor. According to what is stated above, some examples of data crossing and consequent reaction are provided.

By crossing the data of the required clutch coupling point and the need for torque previously detected, in fact, it is therefore possible to determine whether or not there is a need for torque at the clutch coupling point, and therefore act accordingly allowing or not allowing the programmed cycle to be effected.

1) In a first simpler example: it is only known whether or not there is a need for torque, but without measuring the amount.

X = coupling point of the clutch with respect to the cycle reference (e.g. at 120° degrees of rotation angle of the press) Nm = required torque (for example measured in Nm, but there could also be other units of measurement, such as, for example, Joules )

If at 120° Nm > 0 then the cycle should not be allowed

If at 120° Nm = 0 then the cycle can be allowed

2) In a second intermediate example, the amount of torque is measured and the data is crossed with a further pre-established parameter as the limit below which the clutch coupling is allowed as the "defrictioning" generated can be tolerated.

X = clutch coupling point with respect to the cycle reference (e.g. at 120° degrees of rotation angle of the press)

Nm = required torque (for example measured in Nm, but there could also be other units of measurement, such as Joules) Y = a predetermined torque value, greater than 0, establishing a limit within which clutch coupling can be allowed as per the programmed cycle.

If at 120° Nm > Y then the cycle should not be allowed

If at 120° Nm < Y then the cycle can be allowed

3) In a third more refined example, the amount of torque is measured at each point of the cycle by creating a data table and/or a required stress curve linked to the position of the rotation of the kinematic mechanism.

The software functions as in Example 2) but with an additional function: it verifies which point is closest to the B.D.C. where the torque requirement is lower than the pre- established limit value (Y) , indicating to the operator what this point is.

The operator will thus have the right to use this point as a limit in the cycle programming, without having to proceed with various attempts.

With the method according to the present invention, a system for safeguarding the clutch or clutches present in the mechanical press is implemented.

The objective mentioned in the preamble of the description has thus been achieved.

The protection scope of the present invention is defined by the enclosed claims.