WO1997007961A1

WO1997007961A1 - Injection moulding machine

Info

Publication number: WO1997007961A1
Application number: PCT/DK1995/000339
Authority: WO
Inventors: Poul Erik Damkjaer
Original assignee: Uni-Chains International A/S
Priority date: 1995-08-22
Filing date: 1995-08-22
Publication date: 1997-03-06
Also published as: AU3253495A

Abstract

An injection moulding machine (1) having a machine frame (2) with a C-frame (3) comprises a stationary plane (5) and a movable plane (6) for an injection mould (7, 8). The movable plane (6) is connected to a conveying device (10, 11) via a mounting plane (9). The mounting plane (9) and the stationary plane (5) are coupled together at one side by tie rods (17), and both planes (9, 5) are top suspended in the C-frame (3) in swivel joints (20). An open machine is hereby provided, wherein the tie rods do not prevent accessibility to the area between the planes (5, 6), and the planes will be parallel during the moulding process, since the tie rods will ensure that the planes (5, 6) remain parallel, even if the C-frame of the machine frame bends during the moulding process.

Description

INJECTION MOULDING MACHINE

Prior art technique

The invention relates to an injection moulding machine of the type described in the introduction of claim 1.

Injection moulding machines of this type have been known for several years. In recent years injection moulding machines have been further developed into the so-called tie rod-less injection moulding machines, see e.g. U.S. Patent No. 5.249.951 and European Patent Application No. 93300577.9 (Publication no. 0 554 068). An open machine is hereby provided having ample space for large tools, mount¬ ing of robots, operation of tools by robots, injection moulding tools having one or more lateral withdrawal cylin¬ ders, etc.

The prior art tie rod-less machines, however, have a num¬ ber of drawbacks as a consequence of the design without tie rods. Even in a very large and solid machine frame, e.g. a machine frame having a so-called C-frame, bending will occur at large closing pressures, e.g. at closing pressures of 50 tons or more, which cannot be remedied entirely in the prior art machines, even if one or both planes for the injection moulding parts are mounted in a swivel joint in these machines. If the injection mould has not been designed with the injection cavities completely symmetri- cal about the center line or, when moulding large pro¬ ducts, in which case only one part per mould is usually prepared, positioning the part symmetrically around the center line causes difficulties, and a displacement of the moulding parts will occur to the effect that the closure is not complete. This will cause non-uniform strain to the tools with resulting wear and reduced life, as well as non-uniform strain to different machine parts causing wear and reduced life as well. Finally, an incomplete closure of the moulding tools results in the occurrence of flashes in the moulding parts, which must be removed, and the parts will not have precisely the desired dimensions. It will be obvious to a person skilled in the art that the extent of the mentioned problems is proportional to the degree of the closing pressure, as well as to the injection moulding pressure desired. The degree of closing pressure possible in an injection moulding machine is a limiting factor to the size and complexity of the parts to be moulded, even though the space were sufficient for mounting a suffi¬ ciently large mould in the machine.

It is true that the prior art machines have comparatively large planes for mounting of moulds, however, since centering about the center line is required at major closing pressures, part of these planes are not always useful in actual practice.

It should further be pointed out that the prior art tie rod-less injection moulding machines require very large and solid swivel joints or similar devices, which are necessary in order to obtain a reasonable closure of the mould at major closing pressures.

Advantages of the invention

By designing the injection moulding machine according to the invention as indicated in the characterizing part of claim 1, maintenance of the large open area between the planes as is known from the machines without tie rods, is achieved without the drawbacks of the known machines as regards the absence of parallelism between the planes, in particular at major closing pressures. The planes of the machine according to the invention have a higher degree of parallelism during the injection operation as compared to the known, tie rod-less machines, and the accessibility to the area is not reduced, nor is the size of the area between the planes, when these planes are in open position, even when tie rods or similar expansion elements are used in the machine according to the invention.

Since the comparatively large swivel joints used in e.g. in the construction according to U.S. Patent No. 5.249.951 can furthermore be dispensed with, a considerably shorter structural overall length becomes possible, which is of significant practical and economical importance.

Finally, the principle according to the invention can be applied in connection with any type of injection moulding machine, knee-joint machines, as well fully hydraulic machines, which makes the manufacture of machines of any size possible, since there is no immediate limitation in the dimensions of the machine possible to build, both as regards the sizes of the machines as well as the closing pressures.

In addition hereto, the machine according to the invention is inexpensive to manufacture because no complicated devices or the like are introduced according to the inven¬ tion.

By designing the injection moulding machine according to the invention as indicated in the characterizing part of claim 2, a complete compensation for the bending of the machine frame is achieved, to the effect that the strength and design of the materials alone determine the dimensions of the injection moulding machine possible to manufacture, i.e. the power of the closing pressure at which one can operate. The injection moulding machine according to the invention may be designed as indicated in the characterizing parts of claim 3-5. A machine is hereby provided, which fully meets the requirements of a production machine, in particular in the application of large moulds having withdrawal cylin¬ ders, robotic operation, etc.

By designing the injection moulding machine according to the invention, a fully automatic adjustment of the closing action at any moulding cycle and at any closing pressure is achieved. If the machine has been moved, or has been sub¬ jected to interference in other respects, the possibility has been provided for fine adjustment or re-adjustment of the parallelism of the planes by designing the machine as indicated in the characterizing parts of claim 6 or 7.

The injection moulding machine according to the invention is preferably designed as indicated in the characterizing parts of claim 8 or 9, to the effect that a machine can be built according to any dimension and any closing pressure desired.

The drawing

The invention will be explained in detail below with refe¬ rence to the drawing, which illustrates two embodiments for the construction of an injection moulding machine according to the invention, and wherein

Fig. 1 illustrates an injection moulding machine accord¬ ing to the invention in a fully hydraulic design, the machine being illustrated in a lateral view,

Fig. 2 illustrates a vertical, plane section II-II of fig. 1, Fig. 3 illustrates a vertical plane section III-III of fig. 1,

Fig. 4 illustrates an injection moulding machine accord- ing to the invention having a knee-joint closure, the machine being illustrated in a lateral view,

Fig. 5 illustrates a vertical, longitudinal central section of the machine in fig. 4, this section be- ing also marked in fig. 7,

Fig. 6 illustrates a section of the machine illustrated of fig. 5 but in an open position,

Fig. 7 illustrates a vertical, plane section VII-VII of fig. 4, and

Fig. 8 illustrates a vertical, plane section VIII-VIII of fig. 4.

Description of the embodiments

Figs. 1-3 illustrate a fully hydraulic injection moulding machine 1 comprising a machine frame 2 having a so-called C-frame 3, which carries and supports the two planes 5,6, to which the mould parts 7,8 for an injection mould is se¬ cured. The plane 5 with the mould part 7 is stationary during the moulding cycle itself and is top suspended in a swivel joint 20. The mould material is introduced into the mould through a central opening 13 during the moulding cycle, which begins when the mould parts are closed. The part of the machine itself, which relates to heating and melting of the mould material, introduction hereof under pressure, etc. is not illustrated in the drawing and will not be explained in this application since commonly known technique is applied. This will also apply to the embodi- ment, which will be explained later with reference to figs. 4-8.

The second plane 6 is movable, being supported by one or more sliding planes 4 on the machine frame in known manner. Behind the movable plane is provided a stationary mounting plane 9 for mounting a conveying device in the form of a large, hydraulic cylinder 10 having a piston 10', which is secured to the movable plane 6. As is the case with the stationary plane 5, the mounting plane 9 is top suspended by means of a swivel joint 21 in the C-frame of the machine frame.

Two tie rods 17, one on each side, are positioned at the base of the planes 5,9, i.e. at the side of the planes facing down towards the machine frame and the sliding planes 4, said tie rods being in firm but adjustable engagement with the planes 5 and 9. Fastening may comprise means of fastening 18, like e.g. large nuts, threaded devices or the like, which are adjustable. The tie rods 17 can pass the plane 6 through an opening for each tie rod in such a manner that the movement of the plane is not restricted or prevented.

Although the embodiments shown in the drawing illustrate tie rods 17 as the element/the elements, which are provided in order to compensate for the bending of the machine frame, it will be obvious to a person skilled in the art that other types of expansion elements and similar devices can be applied having the same effect, without departing from the basic idea of the invention.

The swivel joints 20,21 enable the planes 5, 9 to move in the directions shown by the arrows 22, 23. The swivel joints may be circular or spherically shaped pro¬ jections, which form guides and swivel joints for the planes, and may furthermore comprise screws, bolts or the like through the projections, to the effect that the planes 9, 5 are secured.

Figs. 4-8 of the drawings illustrate a corresponding machine, wherein the same or corresponding parts have the same reference numbers as in figs. 1-3. The conveying device is a commonly known knee-joint mechanism 11, which is driven by a cylinder 12. Figs. 4 and 5 illustrate the machine in a closed position, and fig. 6 illustrates the knee-joint mechanism, when the machine is in an open position, i.e. with an opened mould 7,8.

The operation of the injection moulding machine according to the invention will be explained below.

Heated and liquid material is injected into the moulding tool 7,8 at the nozzle side, i.e. through the opening 13 of the stationary plane 5, the machine being closed as illustrated in fig. 4 or 5. The injection pressure will exert pressure to open the mould, however, the closing cylinder 10, 10' or the knee-joint device 11 will keep the mould closed, the conveying device providing the necessary closing pressure. During this stage of the cycle the C- frame of the machine frame will be subjected to a large pressure, as a result of which the frame will bend out¬ wards. This bending outwards will exert pressure to open the mould, however, this will not occur since the swivel joints 20 and 21 provide the possibility for the planes turning to a degree which is sufficient for the planes to remain completely parallel since the tie rods 17 underneath will yield as well and expand in a distance which corresponds to the bending degree of the C-frame. The tie rods 17 are thus dimensioned for tension and, in relation to the dimension of the C-frame and the current closing pressure, so dimensioned that the planes 5, 9 and thus the planes 5,6 remain completely parallel, and the mould parts 7,8 will not open during the moulding cycle.

When the injection pressure has been removed, i.e. at the conclusion of the moulding process, the conveying device 10,11 will open the mould, and the moulded part can be removed.

The machine frame, i.e. the C-frame 3, and the tie rods 17 will withdraw automatically to the initial position, i.e. a position without deformations, and a new moulding cycle can begin.

In other aspects the injection moulding machine works on lines similar to those of the known machines.

It will be obvious to a person skilled in the art that the swivel joints 20,21 may be so formed, and that the C-frame 3 as well as the tie rods 17 so designed that any desired parallelism of the planes 5,6 can be obtained and main¬ tained at desired conditions of pressure. It is possible by means of the adjustable fastening means 18 to readjust the machine to desired closing pressures, and it is also possible to make readjustments at suitable intervals, to the effect that the machine according to the invention be¬ comes functional with completely parallel planes 5, 6 during the entire life of the machine.

It will also be obvious to a person skilled in the art that already existing machines can be modified in many cases to the effect that the principle according to the present invention is applied. Any such modification therefore, will therefore also be within the frames of the invention according to the present invention.

Claims

P A T E N T C L A I M S

1. Injection moulding machine (1) comprising a machine frame (2) having a stationary plane ( 5) and a movable ( 6) plane (6) for mounting injection moulding parts (7,8), and wherein the movable plane ( 6) is connected to a conveying device (10,11), which exerts the pressure necessary to close the mould parts and to keep these closed during an injection phase, characterized in that the injection mould- ing machine further comprises a mounting plane (9 ) for the conveying device (10,11), that the mounting plane (9) and the stationary plane (5) carry tie rods (17), expansion elements or similar devices, and that at least one of the planes (9,5) is mounted on or suspended in at least one swivel joint (20) provided at the opposite side of the plane in relation to the fastening of the tie rods, the expansion elements or the devices.

2. Injection moulding machine according to claim 1, characterized in that each of the planes (9,5) are mounted in at least one swivel joint of the machine frame (3).

3. Injection moulding machine according to claim 1 or 2, characterized in that the swivel joints (20) comprise a rounded projection, e.g. a spherically shaped projection, on the machine frame (3) or on the planes (9,5), and that the planes are furthermore mounted in the swivel joints, e.g. by means of bolts, screws or the like.

4. Injection moulding machine according to any of the preceding claims, characterized in that the swivel joints ( 20) are positioned at the side of the plane/the planes (9,5) facing upwards.

5. Injection moulding machine according to claim 1, characterized in that the tie rods (17), the expansion elements or similar devices are positioned at the side of the planes (9,5) facing downwards, i.e. the side facing the machine frame (3) .

6. Injection moulding machine according to claim 1, characterized in that the tie rods (17), the expansion ele¬ ments or similar devices are length adjustable.

7. Injection moulding machine according to claim 1 or 5, characterized in that the tie rods, the expansion elements or similar devices comprise means (18) for length adjust¬ ment hereof, said means being built into or constituting part of their fastening to the planes.

8. Injection moulding machine according to claim 1, characterized in that the machine frame is a so-called C- frame (3), the bottom of which is provided with or formed with sliding faces (4) for support of the movable plane (6).

9. Injection moulding machine according to claim 1 or 8, characterized in that the conveying device is a commonly known hydraulic cylinder mechanism (10, 10' ) or a commonly known knee-joint mechanism (11, 12) adapted to exert a major closing pressure, and that the tie rod/the tie rods (17), the expansion devices or similar devices are made of a material having such properties and such dimensions that only a minimum expansion or displacement of the planes occurs during the injection phase, as a result of the closing pressure of the conveying device, which expansion or displacement corresponds to the degree of bending of the C-frame due to the closing pressure.