Injection moulding machine

[0002] 1. Field of the Invention

[0003] The invention relates to an injection moulding machine as described in the preamble to claim 1. The invention relates in particular to injection moulding machines with very high closing pressures.

[0004] Description of the Prior Art

[0005] Injection moulding machines of this kind are known from the applicant's own earlier International Patent Application no. PCT/DK95/00339. With the configuration disclosed herein, it is possible to maintain a large, open, freely accessible area between the planes in the same manner as is known from machines without tie rods, and still maintain full parallelism between the planes at very high closing pressures, which is very difficult with machines without tie rods. This is achieved without using complicated mechanisms and thus without increasing the costs of the machine to any significant degree. The possibility of adjustment which enables the planes to remain parallel, even at high closing pressures, is achieved by means of tie rods or the like between a mounting plane and the stationary plane, and with at least one swivel joint in the plane's opposite side in relation to that to which the tie rods are secured. These auxiliary tie rods are disposed in such a manner that they do not hinder access to the area between the planes. The pivot links are, for example, rounded projections or the like which rest against a rounded surface.

[0006] A similar construction is known from German Utility Model Publication No. 9421299, but wherein bearings are used where the planes and the tie bars are coupled together. This has several disadvantages, among these being that the bearings get worn by the high pressures and, moreover, have to be adjusted and lubricated, which is very difficult because of the effects of the great pressure.

[0007] A desired function and parallelism is achieved between the halves of the mould completely without any mechanically moving parts, in that the possible turning of the planes is achieved by the resilience of the elastic machine part.

[0008] In the present description, an elastic machine part is to be understood to be a joint-like element without mutually moving parts, i.e. the movement arises solely as a consequence of the machine part's own resilience or possible elastic deformation.

[0009] The machine part according to the invention can withstand even very high pressures without any deformation in the direction of pressure.

[0010] The machine part itself can be configured either as an independent unit or as an integrated unit, where the part is integrated with one of the parts which serve to effect the actual coupling together. Both configurations offer advantages of a practical nature as well as from the point of view of production technique, depending among other things on the construction etc. of the rest of the injection moulding machine.

[0011] The injection moulding machine according to the invention achieves a uniform construction at both sides of the machine, which among other things makes the preceding calculation and construction work more simple.

[0012] An elastic machine has a desired resilience or elasticity and at the same time the possibility is provided of being able to provide securing elements, e.g. threaded holes, in the areas which are not deformed.

[0013] The part is hereby configured as an independent unit which has a practical shape and is simple to produce. It is possible for its configuration to be symmetrical, so that it does not need to be turned in a certain way when being mounted.

[0014] The invention also relates to a specially-configured injection moulding machine with optimized characteristics, having a so-called C-frame self-supporting machine frame as disclosed in claim 9. With the combination of such an injection moulding machine frame configured with tie bars at the bottom of the planes as described above, and an elastic machine part similarly as described above, as far as the parts which must maintain the parallelism between the two halves of the moulding tool are concerned, the resulting injection moulding machine is one without mechanical parts which move in relation to one another during the moulding process. In such a machine according to the invention, the relevant parts, i.e. the C-frame, the tie bars between the planes and the elastic machine part(s), will all be elastic and will yield slightly due to the injection pressure. The individual parts can be dimensioned in such a manner that the elastic expansions, the outward bending etc., completely compensate for each other, and the two halves of the mould remain parallel, even at very high injection pressures. Since the parts do not move mechanically but only elastically in relation to each other, there are no bearings or the like which need to be lubricated or maintained in any way, which is a very great advantage.

[0015] The invention will now be described in more detail with reference to the drawings, in that

[0016] FIG. 1 shows an injection moulding machine with an elastic machine part according to the invention,

[0017] FIG. 1ashows on a larger scale a detail in FIG. 1 regarding the elastic machine part,

[0018] FIG. 2 shows a plane section in the direction II—II in FIG. 1,

[0019] FIG. 3 shows a plane section in the direction III—III in FIG. 1, and

[0020] FIG. 4 shows an example of an elastic machine part according to the invention configured as an independent unit and on the same scale as in FIG. 1a.

[0021] FIGS. 1-3 show a fully-hydraulic injection molding machine 1 comprising a machine frame 2 with a so-called C-frame 3 which carries and supports the two planes 5, 6 on which the mold parts 7, 8 for an injection mold are secured. The plane 5 with the mold part 7 is stationary during the actual molding cycle, and is suspended at the top in an elastic machine part 30 which will be explained in more detail later. During the molding cycle, which starts when the mold parts are closed, the mold material is introduced into the mould through a central opening 13. The part of the machine which effects the actual heating and melting of the molding material, the introduction hereof under pressure etc., is not shown in the drawing and will not be explained in the present application, in that the technique used here is commonly known.

[0022] The second plane 6 is movable, in that it is supported in a known manner by one or more slide planes 4 provided on the machine frame. Behind the movable plane is provided a stationary mounting plane 9 for the mounting of the conveying device in the form of a large, hydraulic cylinder 10 with a piston 10′, which is secured to the movable plane 6. In a manner corresponding to that of the stationary plane 5, the mounting plane 9 is suspended at the top by means of an elastic machine part 30′ in the C-frame of the machine.

[0023] At the foot of the planes 5, 9, i.e. at that side of the planes which faces down towards the machine frame and the slide planes 4, two tie rods 17 are provided, one on each side, said tie rods being in firm but adjustable engagement with the planes 5 and 9. 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.

[0024] Although the conveying mechanism in the present case is a hydraulic cylinder 10, other conveying mechanisms will be able to be used, e.g. knee-joint mechanisms and the like.

[0025] The injection molding machine described above corresponds essentially to that which is described in the applicant's earlier International Patent Application no. PCT/DK95/00339, except for the configuration of the elastic machine part 30, 30′. This part makes it possible for the planes 5, 9 to move in the directions shown by the arrows 22, 23. Together with the tie rods 17, the part 30, 30′ serves to ensure that the planes 5, 9 remain completely parallel, the result being that the mould parts 7, 8 do not open during the moulding cycle, regardless of the degree of pressure used.

[0026] The novel aspect according to the invention lies in the configuration of the elastic machine part 30, 30′, which can for example be configured as shown in the drawing, i.e. with the part as an independent unit as shown in FIG. 4. However, it will be obvious to a person skilled in the art that the elastic machine part will be able to have many other configurations, and will also be able to be configured as a one-piece unit with, e.g. the planes 5, 9, on which they are arranged to be secured.

[0027] The elastic machine part 30, 30′ is made of steel, e.g. as a rectangular rail as shown in FIG. 4, with a central part 34 which is solid, and a longitudinal groove 35 in each side with threaded holes 31 for securing by means of bolts 32, 33, e.g. countersunk bolts as shown in FIG. 1a. The part 30, 30′ must have such a configuration and be of a material, e.g. steel, so that from the strength point of view it is strong enough to withstand the high tensile forces which arise, but at the same time be able to yield slightly if the planes 5, 9 move as shown by the arrows 22, 23. FIG. 4 shows an example of a usable configuration.

[0028] It will be obvious to a person skilled in the art that although the elastic machine part 30, 30′ is configured as an independent unit, the central part 34 will be able to be configured with openings or grooves other than those which are shown in order to increase the possibilities of the part's movement. With the embodiment shown, the movement arises solely as a consequence of the part's own resilience in the form of elastic deformation, without the occurrence of any compression of the part.