EP0492300A2 - Method for adapting the travel measuring units of hydraulic presses for composites, for pressing tools of varying weight and device for applying the method - Google Patents

Abstract

The invention relates to the adapting of travel measuring units to the compression moulds of hydraulic moulding presses, the press ram of which is aligned parallel to a reference plane by support on counterholding cylinder units. The travel pick-ups of the travel measuring units - held in contact with a projection which can be secured in various positions with respect to the press ram - are in this case moved along with the press ram, at least during a time period which begins shortly before the closing of the compression mould and ends shortly after its opening. The invention proposes a procedure and a design which allow first of all the travel pick-ups, designed as measuring rods (11), to be brought into a set end position (stop face 29a) with the compression mould (7, 8) closed and subsequently to adapt and fix the position of the projections, designed as actuating rods (13), with respect to the press ram (11). The moving and actuating operations required for this are executed by means of remote-controllable constructional elements (detaining elements 16, detaining drives 24), so that the adapting of the travel measuring units (26, 27) to differently designed compression moulds can be automated. <IMAGE>

Description

The invention relates to a method for adapting the displacement measuring units to press tools of hydraulic plastic presses of different heights, the press rams of which are aligned parallel to a reference plane by support on counter-cylinder units, the displacement transducers of the displacement measuring units being held in contact with a projection which can be held in different positions with respect to the press ram. be moved with the press ram at least for a period of time that begins shortly before the pressing tool closes and ends shortly after its opening; the invention further relates to a device suitable for carrying out the method.

In the case of the parallel-controlled plastic presses - described in US Pat. No. 4,076,780 and German Offenlegungsschrift 39 15 735 - high-resolution, in particular optoelectronic, displacement measuring units are used to determine the distance between the press table and the press ram, for example, which are outside the range of the multi-part Pressing tool are arranged in the vicinity of the counter-cylinder units and the main components are a measuring head and one of have this scanned glass scale. The high-resolution path measurement is carried out only during the period during which the parallel control brought about by the counter-cylinder units is effective. A stroke of the press ram in the order of magnitude of at most 100 mm is generally assigned to this time span; the closing movement of the press ram comes to a standstill at the latest when the mold halves of the press tool are supported directly against one another (for example over so-called distances) in the direction of the press ram stroke.
Since the corresponding displacement measuring units are accordingly only designed for a stroke of up to approximately 150 mm, care must be taken to ensure that the displacement measurement can be carried out over the required period of time even when pressing tools with different height dimensions are used. With regard to the operational safety and measuring accuracy of the displacement measuring units, it must also be taken into account that under certain circumstances the position of the measuring plane - for example due to an unexpectedly high pressing force - can deviate from that of an assumed reference plane; The displacement measuring units must therefore be designed with the best possible use of the available measuring range in such a way that this is not exceeded even in exceptional cases.

So far, the adaptation of the high-resolution displacement measuring units to differently designed pressing tools has been brought about by the fact that the projections arranged on the press ram - which are designed as lockable actuating rods - are adjusted either manually or remotely via actuators due to additional displacement measurements depending on the geometry of the new pressing tools have been. The displacement measuring units, the displacement transducers of which are temporarily carried over the actuating rods during the closing process, are held in an upper end position by means of return springs or are held in contact with the actuating rods.
The disadvantage of this prior art can be seen in the fact that either remote control and thus automatic adaptation is not possible or that the latter entails a considerable technical outlay.

The invention is based on the object of specifying a method for adapting the displacement measuring units to pressing tools of different heights and a device suitable for carrying out the method, which allow at least one remote control with reasonable effort.
The required components should be of simple construction, less prone to failure and, if possible, also commercially available.

The object is achieved by a method which has the features of claim 1. The adaptation to the height dimension of a new pressing tool is then initiated in that it is completely closed - for the purpose of defining a reference plane; the mold halves come into direct contact with one another in the direction of the press ram stroke - in the usual way over distances attached to them. In the normal case, the projections are released before the closing process is initiated by releasing their locking element in such a way that (in the simplest case under the influence of their own weight, but possibly also under the action of a reset, for example in the form of a spring element) within a predetermined path section relative to Press ram can move in the direction of the displacement sensor. To Lowering of the displacement transducers by actuating an adjustment drive into a lower target end position predetermined by a resilient stop, the projections which come to rest on the displacement transducers are held in the now adapted support position by closing the locking element. The system of the displacement transducers on the projections required for carrying out the displacement measurement is brought about by switching the adjustment drive to the lifting state: under the influence of the lifting force acting on the displacement transducers, these temporarily join in the movement of the projections, with the tracking path through the upper end position of the adjustment drive is limited.
Since a reference plane can be easily created by closing the press tool in the empty state and the devices - locking element and adjustment drive - required for the adaptation of each displacement measuring unit can be remote-controlled, the adaptation of the displacement measuring units can be automated by using suitable control elements (valves, limit switches, time switches) will. By supporting the displacement transducers in the lower target end position on a resilient stop, it is ensured that the displacement measuring units can, if necessary, carry out a residual stroke beyond the target end position. The method according to the invention can be carried out regardless of whether the associated measuring head is movable or stationary.
In the context of the solution according to the invention, it may also be possible to proceed such that the locking elements of the projections are only released in the empty state during the aforementioned closing movement of the pressing tool. The release should be brought about before the projections which are moved with the press ram are supported on the respectively associated displacement transducers.

The above-mentioned object is further achieved by a device with the features of claim 2. The projections designed as actuating rods can be held in place with respect to the press ram by means of clamping cylinder units. The displacement transducers consist of measuring rods aligned with the actuating rods, the movement of which in the direction of the press ram stroke is converted into a measuring signal via a measuring head and which can be acted upon alternately in both directions with drive energy by means of a double-acting drive cylinder unit. Another essential feature of the invention is that the lower target end position of the measuring rods is determined by a resilient stop.

At least one of the two cylinder units, namely the drive cylinder unit, is preferably designed as a compressed air unit (claim 3); this makes it possible, if necessary, to support the measuring rods resiliently on the counter surface that is possibly in question, namely on the associated actuating rod or on the associated stop. This should be such that its restoring force is greater than the force acting in the direction of it from the measuring rod (claim 4), which is composed essentially of the pressure force generated by the drive cylinder unit and the dead weight acting on the measuring rod.

The drive cylinder unit is expediently designed in such a way that its larger piston surface is pressurized in the stroke state (claim 5). In this way, each measuring rod is held with sufficient security on the associated actuating rod of the press ram during the period of parallel control.

The device can be further configured in that the measuring rod is part of an adjustment frame which is movably guided with respect to the press frame via ball bearings and on which the piston rod of the drive cylinder unit acts (claim 6).

The clamping points of the actuating rods are preferably designed as slide bearings, on which the clamping cylinder unit acts at least indirectly in the clamped state (claim 7).
The clamp connection should be designed in such a way that the entrainment force that it generates in the event of a fault is less than the force that would destroy the displacement measuring unit or cause the actuating rod to buckle.
The slide bearing can in particular be formed by a DU bushing, which at the same time ensures that slipping of the actuating rod in the event of a fault does not damage its surface.

Fig. 1

stark schematisiert den grundsätzlichen Aufbau einer Kunststoffpresse mit Parallellaufregelung.

Fig. 2

schematisiert den Aufbau und die Anordnung der Bestandteile, die für die Anpassung der Wegmeßeinheiten der Kunststoffpresse an Preßwerkzeuge mit unterschiedlicher Höhenabmessung von Bedeutung sind.

The invention is explained below with reference to the drawing.
Show it:

Fig. 1

highly schematized the basic structure of a plastic press with parallel control.

Fig. 2

schematizes the structure and arrangement of the components that are important for adapting the displacement measuring units of the plastic press to pressing tools with different height dimensions.

The hydraulic plastic press shown in Fig. 1 - for example for production of pressed parts made of fiber composite materials - in addition to four counter cylinder units 1 (two of which are perpendicular to the drawing plane next to each other), a press frame 2 with a press table 3 and a press ram 4, which can be moved in the vertical direction via a hydraulic press drive 5 (double arrow 6) at the top Crosshead 2a of the press frame is held. Opposite him, the press table 3 is attached to the side parts 2b.
Parts 4 and 3 each carry a mold half of the pressing tool, namely the upper mold half 7 and the lower mold half 8 resting on a heating plate 9; these limit one another during the pressing and curing process a mold cavity producing the pressed part.

The parallel operation of the press ram 4 with respect to the press table 3 is brought about in that the former is supported on the counter-holding surfaces 1a of the counter-holding cylinder units facing it, which are equipped with a control system, not shown. The distance between the press table 3 and the press ram 4 - and thus the orientation of the part 4 with respect to a reference plane (for example the reference plane 8a on the lower mold half) - can be determined at least temporarily by means of four displacement measuring units 10 which are outside the region of the mold halves 7 and 8 are each arranged in the vicinity of a counter cylinder unit 1.
Each displacement measuring unit 10 basically consists of a movable displacement sensor in the form of a measuring rod 11, which is held in a housing 12; this in turn is attached to the press table 3.
The measuring rods 11 are held in contact with projections of the press ram 4 over a predetermined path section, which act as actuating rods 13 are trained.
As soon as the mold halves 7 and 8 have approached each other sufficiently during the closing movement of the press ram 4, the actuating rods 13 come into contact with the measuring rods 11 and in extreme cases carry them along until the mold halves 7 and 8 move in the direction of the press ram stroke ( see arrow 6), for example, support each other directly at reference plane 8a. The movement of the pressing rods 11 with respect to their housing 12 triggers the generation of measurement signals which are used in a manner known per se for aligning the press ram 4 via the counter-cylinder units 1.

Each actuating rod 13 is supported by a slide bearing in the form of a DU bush 14 in an extension 4a, which is part of the press ram 4 and to which a clamping cylinder unit 16 is fastened via webs 15 (FIG. 2). Due to the biasing force of a return spring 17 which acts on the piston 16a on the side facing away from the press ram 4, the extension 4a is deformed under the action of the piston rod 16b in such a way that a clamping point holding the actuating rod 13 forms.
By actuating a changeover valve 18, the side of the piston 16a facing the press ram 4 can be alternately connected to a compressed air source 20 via a pressure line 19 or can be depressurized via a return line 21; the pressurization via the pressure line 19 has the consequence that the parts 16a, 16b move to the left, as a result of which the actuating rod 13 is released; their freedom of movement with respect to the press ram 4 in the direction of the associated measuring rod 11 is limited by a paragraph 13a.

Each measuring rod 11 is part of an adjusting frame 22 which is held movably with respect to the press frame (for example the press table 3) via ball bearing guides 23 and on which the piston rod 24b of a double-acting drive cylinder unit 24 acts; this is - like the ball bearing guides 23 - fixed within the housing 12 via partitions 25.
The adjustment frame 22 has, on the side facing away from the measuring rod 11, a glass scale 26 which is scanned by a measuring head 27 which is stationary with respect to the housing 12 and whose displacement corresponding to the movement of the measuring rod 11 triggers the generation of measuring signals; these can be fed via a signal line 28 along with connection 28a for further evaluation.
Below the measuring rod 11 aligned with the actuating rod 13, a resilient stop 29 is arranged inside the housing 12, by means of which the lower desired end position of the part 11 is determined.

The drive cylinder unit 24 is connected via two lines 30, 31 to a changeover valve 32 which is preceded by a pressure line 33 together with a compressed air source 34 and from which a return line 35 which is kept unpressurized originates. By actuating the changeover valve 32, one of the two lines 30, 31 can alternately be pressurized with compressed energy via the compressed air source 34, while at the same time the other line via the return line 35 is relieved of pressure.
When line 31 is pressurized, the larger piston area 24c of the piston 24a is occupied with drive energy, with the result that the adjusting frame 22 together with the measuring rod 11 is a Tried to perform upward movement; this is possibly interrupted or hindered by the fact that either the measuring rod 11 comes into contact with the actuating rod 13 or the adjusting frame 22 via a stop surface 22a on the housing 12.
During the measuring process, the line 31 is pressurized so that the measuring rod 11 - after sufficient lowering of the press ram 4 in the direction of the press table 3 comes into contact with the actuating rod 13 - by the latter when the closing movement continues, counter to the restoring force emanating from the drive cylinder unit 24, is carried along and thereby triggers corresponding measurement signals via the glass scale 26 and the measuring head 27.
By pressurizing the line 30, the adjusting frame 22 together with the measuring rod 11 can be lowered until it rests on the resilient stop 29. Whose spring constant is dimensioned considerably larger than that of the drive cylinder unit 24 when the smaller piston surface 24d is pressurized: The stop 29 is thus compressed at most slightly by the force acting on it from the measuring rod 11 in the direction of it and therefore has a stroke reserve which, in an emergency, has a further one Downward movement of parts 11, 22 and 26 allows.

To adapt the displacement measuring units 10 to a newly installed pressing tool (with the mold halves 7, 8), the subject matter of the invention is handled as follows:
Starting from the open position (cf. Fig. 1), the actuating rods 13 are released by pressurizing their clamping cylinder unit 16 via the pressure line 19, so that they act under their own weight relative to the press ram 4 (or to the extension 4a) within one given path section in Can move towards the associated measuring rod 11; the end of the path section is determined by the paragraph 13a located above the extension 4a. By lowering the press ram 4, the pressing tool is now closed in the empty state to such an extent that its mold halves 7, 8 are supported against one another in the direction of the press ram stroke, for example at the reference plane 8a. Then the measuring rods 11 serving as displacement transducers are lowered by pressurizing the line 30 by means of the drive cylinder unit 24 into a lower desired end position, which is predetermined by the resilient stop 29; due to the configuration of this stop, the target end position approximately corresponds to the position of the end face 29a facing the measuring rod 11.
With the pressing tool still closed, the actuating rods 13, which are supported on the respectively associated measuring rod 11, are immovably held in the thereby predetermined support position by closing their clamping cylinder unit 16 with respect to the press ram 4. This is done in that the supply of compressed air via the pressure line 19 is interrupted by actuating the changeover valve 18 and the clamping cylinder unit 16 is connected to the return line 21.

By switching the drive cylinder units 24 to the stroke state - that is, by actuating the changeover valve 32 with pressurizing the line 31 and relieving the pressure on the line 30 via the return line 35 - the measuring rods 11 are affected by the lifting force then acting on them (interaction of the parts 24a, 24b and 22 ) resiliently held in the sense of a tracking on the actuating rods 13, the tracking path - ie the freedom of movement with respect to the housing 12 - through the upper End position of the drive cylinder unit (in the exemplary embodiment predetermined by the stop surface 22a) is limited.
If the press ram 4 with the held actuating rods 13 executes an upward movement which is greater than the tracking path of the measuring rods 11, the actuating rods 13 are finally lifted off the measuring rods 11. A renewed contact between the parts 13 and 11 takes place only after the press ram 4 has moved sufficiently close to the press table 3 in the course of its closing movement.

The advantage achieved by the invention is that the measuring rods 11 can be brought into a lower desired end position with simple means when the pressing tool is closed and the position of the actuating rods 13 with respect to the press ram 4 can be adapted to the height dimension of the pressing tool in question. The necessary displacement and / or locking of the interacting actuating rods and measuring rods can be brought about by means of remote-controlled components, so that the adaptation to differently designed pressing tools is readily suitable for automation. By using a resilient end stop to support the measuring rods in the lower target end position, the risk of damage to the displacement measuring units is at least largely eliminated, since the measuring rods additionally have a stroke reserve.

The invention can also be designed in such a way that the clamping cylinder units 16 are released in the empty state only after the closing movement of the press tool has been initiated, ie the actuating rods 13 are released during the closing movement with respect to the press ram 4.
To ensure that the released Actuating rods 13 relative to the press ram 4 or to the extension 4a to move in the direction of the associated pressing rod 11, the actuating rods 13 may also be provided with a reset within the scope of the invention. This can consist in particular of spring elements which generate a restoring force which acts on the actuating rods 13 and acts in the direction of the measuring rods 11.

Claims (7)

Method for adapting the displacement measuring units to press tools of hydraulic plastic presses of different heights, the press rams of which are aligned parallel to a reference plane by support on counter-cylinder units, the displacement transducers of the displacement measuring units being held in contact with a projection which can be held in different positions with respect to the press ram - at least for a period of time are moved along with the press ram, which begins shortly before the pressing tool closes and ends shortly after its opening,
characterized by the following process steps: - Before the pressing tool (7, 8) is closed in the empty state to such an extent that its mold halves (7, 8) are supported against each other in the direction of the press ram stroke (arrow 6), the projections (13) are released by releasing their locking element (16) released in such a way that they can move relative to the press ram (4) in the direction of the travel sensors (11) within a predetermined path section; - The displacement transducers (11) are lowered by actuating an adjusting drive (24) into a lower target end position (stop surface 29a), which is predetermined by the springback of a stop (29); - With the pressing tool (7, 8) still closed, the projections (13) that come to rest on the displacement transducers (11) are held in this supporting position by closing the locking element (16); - By switching the adjustment drive (24) in the lifting state, the displacement transducers (11) are then acting on them in the sense of a lifting force Tracking on the projections (13) held in contact, the tracking path being limited by the upper end position of the adjustment drive (24). Device for carrying out the method according to claim 1 on hydraulic plastic presses, the press ram of which is aligned parallel to a reference plane by support on counter-cylinder units, the displacement transducers of the displacement measuring units being held in contact with a projection which can be held in different positions with respect to the press ram, at least for a period of time be moved along with the press ram, which begins shortly before the pressing tool closes and ends shortly after its opening, characterized in that the projections designed as actuating rods (13) can be held with respect to the press ram (4) by means of clamping cylinder units (16);
that the displacement transducers consist of measuring rods aligned with the actuating rods (13), the movement of which in the direction of the press ram stroke (arrow 6) is converted into a measuring signal via a measuring head (27) and which are alternately in both directions by means of a double-acting drive cylinder unit (24) can be acted upon by drive energy; and
that the lower target end position of the measuring rods (11) is determined by a resilient stop (29). Apparatus according to claim 2, characterized in that at least one of the two cylinder units (16, 24), namely the drive cylinder unit (24), is designed as a compressed air unit. Apparatus according to claim 3, characterized in that the restoring force of the Stop (29) is greater than the force acting in the direction of it from the measuring rod (11). Device according to at least one of the preceding claims, characterized in that the larger piston surface (24c) of the drive cylinder unit (24) is pressurized in its stroke state. Device according to at least one of the preceding claims, characterized in that the measuring rod (11) is part of an adjusting frame (22) which is movably guided with respect to the press frame (2) via ball bearings (23) and on which the piston rod (24b) of the drive cylinder unit (24) attacks. Device according to at least one of the preceding claims, characterized in that the clamping points of the actuating rods (13) are designed as slide bearings, on which the clamping cylinder units (16) act at least indirectly in the clamped state.

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