Die closing device of an injection molding machine

Details Die closing device of an injection molding machine Die closing device of an injection molding machine

1997-10-03

2001-11-06

Mackey, James P. (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

Female mold and charger to supply fluent stock under...

With means to close mold

C100S281000, C425S451500

Reexamination Certificate

active

06312249

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to injection molding machines and, more particularly, to a die closing device which has a stationary die backplate or clamping plate and a movable die clamping plate driven by a toggle lever.
2. Discussion
Injection molding machines generally have a movable die clamping plate and at least one stationary die clamping plate. Depending on the driving means, such so-called two-platen machines can be used, although the driving means may itself be supported on a third auxiliary plate.
When two-platen machines without tie bars are employed, an important consideration is the parallelism of the mold, i.e. the correspondence or coordination of the die clamping plates. German patent publication DE 43 08 962 A1 discloses an injection molding machine wherein force transmission elements are constructed as separate deformation elements in the form of stirrups. The support plate is mounted at the machine base for movement in the closing direction.
Due to repeated deformations in normal use, the elements of these machines are subject to extensive wear and thus have a short service life. Furthermore, the deformation is force-dependent and the parallelism of the mold is, accordingly, not always provided.
European Publication 0 554 068 discloses an injection molding machine with a closing device wherein the stationary and movable die clamping plates are connected to each other through stirrups or clips and the force is imparted through the principal axis of the machine.
When a toggle lever drive is used for the closing device, a support plate is used as a third plate.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a low-wear and reliable mold or die closing device which includes a mechanism to ensure that the die clamping plates of the device maintain a high degree of parallelism.
In a presently preferred embodiment, the die closing device of a mold injection machine comprises a stationary die clamping plate and a movable die clamping plate driven by a toggle lever assembly. The toggle lever assembly includes first and second connecting rods. The first connecting rod is pivotally connected to the stationary die clamping plate, and the second connecting rod is pivotally connected to the first connecting rod at one end and to the movable die clamping plate at another end. A drive unit is connected to the first and/or second connecting rods for operatively opening and closing the mold by controlling the motion of the movable die clamping plate.
In another embodiment, the die closing device has at least one toggle lever pair or assembly which includes a first connecting rod that is pivotally connected with the stationary die clamping plate and a second connecting rod that is pivotally connected with the movable die clamping plate. A drive unit is coupled to at least a portion of the toggle lever pair for operatively opening and closing the die or mold. The toggle lever drive is connected, as by a connecting rod, at both ends to the closing device and directly connects the stationary die clamping plate with the movable die clamping plate in a frictional engagement. The connecting rod may be constructed as a cross-beam or substantially C-shaped member.
In still another embodiment, a rotary drive or a linear force unit is provided as the driving means for moving the toggle lever pair. This drive unit can be arranged between one of the connecting rods and the machine bed or die clamping plate or between the two connecting rods.
When a rotary drive is used, the rotary drive acts on one of the shafts connected with the connecting rods and can be supported on a die clamping plate—preferably at the movable die clamping plate—or may alternatively be provided between the two connecting rods of the toggle lever pair.
In yet another embodiment, the shaft is constructed as an eccentric member. In this manner, the closing device can be operated with a rotary drive or a linear drive unit using only a small force so that the closing force is applied by way of simple rotation of the eccentric.
In still another embodiment, the eccentric is arranged so that the closing operation of the closing device, including the application of the closing force, is carried out in a pivotal movement of a connecting rod. In both of the aforementioned embodiments, the eccentric may be driven by an electric drive.
The eccentricity e is dependent upon the total stroke or lift H and is in the range of e=0.005 H to 0.02 H.
In accordance with another advantageous construction, a spacer or distancer may be arranged between the die clamping plate and the toggle lever drive. The spacer may be constructed as a piston-cylinder unit, e.g. a short-stroke cylinder, and serves substantially to apply the closing force. The closing force can be monitored in a particularly simple manner such, for example, as through a closed loop control mechanism. Thus, with respect to the required closing force, the system is free from such changes in the mechanical system as those results, by way of example, from wear or longitudinal deformations of the connecting rods, particularly of the cross-beam or of the longer C-shaped connecting rod or toggle lever member.
In addition to the spacer, a stroke-adjusting device may be provided for adjusting the die stroke. The spacer may also be constructed for use in adjusting the die stroke and, in addition, in applying the closing force.
In a still further embodiment, one of the connecting rods is constructed as a linear force unit; the toggle lever pair may be connected to a rotary drive or a linear drive for this purpose. The structural connection between the connecting rod and the die clamping plate can be constructed in a particularly simple manner.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not drawn to scale and, as such, are merely conceptual in disclosing the preferred embodiments of the invention.


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patent: 295 13 862 (1996-02-01), None
patent: 0 554 068 (1993-08-01), None
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