WO2004041509A1

WO2004041509A1 - Column injection moulding press for plastics materials

Info

Publication number: WO2004041509A1
Application number: PCT/IT2002/000703
Authority: WO
Inventors: Gino Soncini
Original assignee: Oima S.P.A.
Priority date: 2002-11-07
Filing date: 2002-11-07
Publication date: 2004-05-21
Also published as: AU2002354323A1

Abstract

A column injection moulding press (1) for plastics materials comprising a moving plane (5) which is caused to slide along the columns (4) away from and towards a closed position in which a mould (6, 7) is closed between the moving plane and a fixed plane (3) with a tightening load supported by the columns. Actuator means comprising a rack (10) of one piece with the corresponding column (4) and a pinion (13) supported on the moving plane are provided to move the moving plane along the columns. The pinion (13) engages the rack and is caused to rotate by motor means (15).

Description

Column injection moulding press for plastics materials Technical scope of the invention

This invention relates to a column injection moulding press for plastics materials of the type incorporating the characteristics mentioned in the precharacterising clause of the principal claim. Technological background

Presses of the aforesaid type are known, for example, from European patent EP 387496 by the same applicant. In these presses (relatively fast and long stroke) double-acting hydraulic jacks are used to move the moving equipment (which includes the moving plane and the devices applying the tightening load) of the press away from and towards the fixed equipment (which includes the fixed plane and the corresponding die) during the closing/opening travel of the press. Other further (relatively slow and short stroke) jacks are also used to apply the tightening load once the moving plate has been immobilised against the columns in the closed position for the mould.

These hydraulic jack systems nevertheless give rise to not a few disadvantages as regards movement and guidance of he moving equipment in the press. Above all they do not permit effective control of the position of the moving equipment and in particular control over the approach speed, so that for example when two diagonally opposite jacks are used dissimilar thrusts may be produced on the two sides of the moving equipment tending to force it to slide against the columns of the press.

In addition to this the jacks obstruct access to the press, particularly with reference to the dies. Furthermore the jacks, although fast, have limitations in the dynamics of moving the moving plane in the press (particularly during acceleration stages) which have an adverse effect on productivity. Finally they require pressurised oil feed and drain circuits which complicate the press structurally and result in undesired bulk and obstructions. Description of the invention

The problem to which this invention relates is that of constructing a column injection moulding press for plastics materials which is structurally and functionally designed to overcome the abovementioned limitations in relation to the known art mentioned.

In the context of this problem a primary object of the invention is to provide a column press in which the movement of the moving plane is controlled and managed so as to maintain the latter horizontally parallel and vertically parallel at all times.

A further object is to provide a column press which requires less energy consumption for its operation.

This problem is resolved and these objects are accomplished by the invention through a column press realized in accordance with the following claims.

Brief description of the drawings

Other advantages and characteristics of the present invention will become clear from the following detailed description which is given with reference to the appended drawings which are provided purely by way of non-limiting example and in which :

- Figure 1 is a diagrammatical perspective view of a column press constructed according to this invention,

- Figures 2 and 3 are diagrammatical lateral elevation views of the press in Figure 1, in two different operating positions, - Figure 4 is a view of a detail of the press in Figure 1 in cross-section and on a magnified scale. Preferred embodiment of the invention

In the figures, 1 indicates a column injection moulding press for plastics materials constructed in accordance with this invention, as a whole. Press 1, which is only partly illustrated in the appended drawings, comprises in a manner which is in itself known a base 2 from which is erected a fixed plane 3, generically of quadrangular shape, to which are integrally secured a plurality of columns 4, all extending concordantly in a direction X substantially parallel to base 2 from fixed plane 3. A moving plane 5, of similar shape to fixed plane 3, is slidably supported on base 2 by means of slide blocks 2a and is also guided in sliding along direction X by columns 4 which for this purpose pass through corresponding holes 8 provided in the vicinity of the corners of moving plane 5. The whole is designed to close and then reversibly tighten two corresponding dies 6, 7 incorporated therewith between fixed plane 3 and moving plane 5, applying a tightening load to them in the ways illustrated below. Actuator means which, according to the invention, comprise one or more racks 10 located within a corresponding longitudinal groove 11 constructed along a generatrix of each column 4 are provided in order to effect the relative movement between the fixed plane 3 and the moving plane 5 in direction X. A corresponding pinion 13 is rotatably supported on moving plane 5, directly on or behind it, and engages the corresponding rack 10 in such a way that as a result of rotation of the pinion about its own axis perpendicular to direction X there is corresponding rotational/translational movement of pinion 13 with respect to rack 10 and consequent lateral movement of moving plane 5 with respect to columns 4 in direction X. Motor means indicated diagrammatically by 15, attached for example to the sides of moving plane 5, which are connected separately and independently (Figure 1) or in pairs to pinions 13, control the rotation of pinions 13. Obviously all pinions 13 are synchronised in rotation with each other so that the thrust displacing moving plane 5 with respect to columns 4 is delivered uniformly to the four corners of the same, thus achieving uniform advance of plane 5 in direction X. Although these may also be of the hydraulic, electromechanical or similar type, motor means 15 are preferably of the electrical type, thus making control of position and any adjustment of moving plane 5 with respect to each column 4 easier.

In the course of the displacement of moving plane 5 towards fixed plane 3, in fact, the position of plane 5 is constantly checked so that it is perpendicular to direction X and the possibility of acting on individual pinions 13 makes it readily possible to correct any divergences from ideal behaviour. It is also known that in order not to make the structure hyperstatic the coupling between moving plane 5 and each column 4 at holes 8 is relatively loose. Consequently columns 4 act predominantly as tie rods, being substantially released from the function of guiding moving plane 5.

In order to counter the engaging pressure between the teeth of pinion 13 and corresponding rack 10, a further recess 20 is provided in column 4 opposite groove 11 and coextensive therewith. A companion member 21, such as for example a slide block or a roller, which is of one piece with moving plane 5, the purpose of which is to relieve columns 4 of any stresses having deviant components with respect to the required longitudinal direction, is housed in and engages recess 20.

Dies 6, 7 are brought up against each other (see Figure 2) and moved away from each other for opening the mould (see Figure 3) by this means. It is not however provided that the load for tightening the mould be applied through the actuator means described above. Means for applying the tightening load which, in the embodiment illustrated, comprise a corresponding sleeve 30 for each column 4 placed behind moving plane 5 and mounted thereon, which can be tightened on command against corresponding column 4 to immobilise it thereupon, opposing the tightening load, are responsible for this. In order to achieve relative immobilisation between column 4 and corresponding sleeve 30, the latter incorporates a pair of jaws 31, 32 which can move radially away from and towards corresponding column 4. On the inside surface of jaws 31, 32 are provided two or more threaded or toothed sections 31a, 32a, having a saw-tooth profile, the corresponding backs of which placed against fixed plane 3 are suitably perpendicular to direction X. Each column 4 has on its outer surface 18 corresponding teeth or a thread 17 of a shape matching sections 31a, 32a, which is capable of engaging with jaws 31, 32 to immobilise sleeve 30 with respect to column 4. In this way, in order to axiaily immobilise sleeve 30 on column 4, it is sufficient to move jaws 31, 32 towards surface 18 engaging thread 17 (Figure 2), while in order to permit free axial sliding along column 4 it is sufficient to radially displace jaws 31, 32 away from surface 18 (Figure 3). The means for applying the tightening load further comprise a hydraulic jack 19 provided annularly around each column 4, between moving plate 5 and corresponding sleeve 30. By feeding pressurised oil to jack 19 the desired tightening load is applied to moving plate 5 and through that to the two dies 6, 7, bringing about accurate closure of the mould. It will be noted that, because the tightening load is applied to the mould which has been closed through the effect of the approach brought about through the actuators incorporating rack 10 and pinion 13, a very small provision of pressurised oil is sufficient to ensure very high tightening loads because substantially no movement of the plate, which is already in the closed position of the mould, is involved. The fact that the inventive concept in the invention already described in detail with reference to a column press of the type having two planes can similarly also be applied to a column press of the type having three planes will also be appreciated. The invention thus achieves the proposed object and provides numerous advantages in comparison with conventional presses, among which the possibility for effective control and management of the parallel position of the moving plane in both a horizontal and a vertical direction as it moves along the columns. A second advantage lies in the fact that, particularly when the motor means are of the electric type, the response to the movement command is decisively more prompt than in conventional presses, so that overall cycle times are reduced.

A third advantage found in presses constructed according to this invention, in particular when the motor means are of the electric type, comprises a substantially reduced requirement for power. Tests carried out by the applicant have in fact shown an energy saving of between 20% and 30% in comparison with conventional hydraulically operated column presses.

Claims

1. A column injection moulding press for plastics materials comprising a^' moving plane (5) which is caused to slide along the said columns (4) away from and towards a closed position in which a mould (6, 7) is closed between the said moving plane and a fixed plane (3) with a tightening load supported by the said columns, actuator means acting on the said moving plane to move it along the said columns and means to apply the tightening load, characterized in that the said actuator means comprise, for at least some of the said columns, a rack (10) which is of one piece with the corresponding column (4) and a pinion

(13) supported on the said moving plane (5), the said pinion engaging the said rack and being caused to rotate by motor means (15) to move the said moving plane along the said columns.

2. A press according to claim 1, in which each of the said columns is equipped with the said actuator means.

3. A press according to claim 1 or 2, in which the said motor means (15) are mounted on the said moving plane (5).

4. A press according to any one of the preceding claims, in which the said motor means are of the electric type.

5. A press according to any one of the preceding claims, in which on one of said moving plane (5) and said column (4) there is provided opposite said rack (10) a recess (20) and on the other of the said moving plane and the said column there is provided a companion member (21) which engages and slides within the said recess (20).

6. A press according to any one of the preceding claims, in which the said means for applying the tightening load comprise at least one sleeve (30) forming one piece with the said moving plane (5) and fitting upon said column (4) which is capable of becoming immobilised on the said column opposing the tightening load.

7. A press according to claim 6, in which the said sleeve (30) incorporates a pair of jaws (31, 32) which can be displaced radially away from and towards the said column (4), a profile (31a, 32a) which axiaily engages a matching profile (17) provided on an external surface (18) of the said column being provided on an internal surface of the said jaw. A press according to claim 7, in which a saw-tooth profile is provided on said jaws (31, 32).