Plastic article or earthenware shaping or treating: apparatus – Mold opening and closing means and segmented female mold – Articulated link
Reexamination Certificate
1999-01-29
2001-05-01
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Mold opening and closing means and segmented female mold
Articulated link
C425S451700, C425S451900, C425S541000
Reexamination Certificate
active
06224367
ABSTRACT:
FIELD OF THE INVENTION
My present invention relates to a mold closer for an apparatus producing articles from thermoplastic synthetic resins and especially for blow molds capable of producing hollow articles of thermoplastic materials and for use in a blow-molding machine. More particularly, the invention relates to a mold closer of the type in which two mold halves are brought together by linear shifting and especially where the mold closer is capable of synchronously displacing the two mold halves toward and away from one another.
BACKGROUND OF THE INVENTION
A mold closer is described in German patent document DE-A1 37 22 340 for synchronously displacing the two mold halves toward and away from one another for the production of articles from thermoplastic synthetic resins. The apparatus described in this publication has at least one draw rod and a pressure rod, between the ends of which respective yokes are connected, the yokes forming a frame. The draw rod and the pressure rod are mutually parallel and extend in the displacement direction while the yokes extend transversely to this direction and mounting plates are provided to carry the respective mold halves which are displaceable by this mechanism toward and away from each other.
One of the yokes has a cantilever arm which directly engages one of the mold-mounting plates while the other yoke acts upon the second mold-mounting plate through a force-transmitting mechanism. The force-transmitting mechanism is provided on a frame which is suspended from a spatially-fixed housing formed with guide beams separate from the frames and enabling separate movements of the frames. As a consequence the mechanism generating the closing force and the guides for the mold-mounting plates can be decoupled from one another and hence the frame which is affected by the force-transmitting mechanism or carries the latter can be free to deform without affecting the guidance of the mold-mounting plates.
However with this system a precisely synchronous displacement of the mold-mounting plates may not be guaranteed since the mechanism generating the closing force may not act exactly symmetrically on both of the mold-mounting parts.
The synchronous action, moreover, is generated by a hydraulic or pneumatic piston-and-cylinder arrangement which frequently permits a shift in the predetermined calibration position at which mold closing is to occur.
The mold-closing apparatus can, of course, be mounted on a carriage or like transporter which enables the entire mold assembly to shift between, for example, an extrusion station at which a parison can be produced and the blowing station.
As a general matter, moreover, the earlier mold-closing mechanisms, to the extent that they have attempted to ensure synchronous displacement of the mold halves and a precise mold-closing position, have been relatively massive and complex. Moreover, in mold-closing systems of this type it has been difficult to ensure that the mounting plate for a mold half which is relatively distal to the force-generating unit is acted upon symmetrically to the mold-carrying plate which is proximal to that unit. As a result, either deformation of the guiding or guided members could not be entirely avoided or significant structure was required to minimize such deformation.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide a mold-closing system in which the aforementioned drawbacks are avoided and, more specifically, wherein the mold closing apparatus has a relatively simple construction and can exclude asymmetric closing forces which tend to undesirable deformation.
Another object of this invention is to provide a low-cost mold-closing apparatus which ensures not only synchronous displacement of the two mold-carrying members but also precludes deformation of the guides or guided portions resulting from asymmetrical closing forces.
Still another object of the invention is to provide an improved mold closer, especially for blow molds, whereby the mold closing is carried out with greater precision, uniformity and force symmetry than heretofore.
SUMMARY OF THE INVENTION
These objects are attained in accordance with the invention in a mold-closing system in which each of the two mold halves is mounted on a respective yoke and both of the yokes are directly operated upon by the force-generating unit. More particularly, the mold-closing apparatus can comprise:
two linearly shiftable mutually juxtaposed yokes;
respective halves of a mold for shaping thermoplastic articles each mounted on one of the yokes; and
a linear force generator acting directly on each of the yokes in line with a direction of shifting movement thereof for selectively drawing the yokes together and displacing the yokes apart to close and open the mold.
With the system of the invention, there is no lever effect at the side of the system remote from the force-generating unit, i.e. the rear yoke, and no tendency toward deformation of the guide or guided member. The closing force is applied symmetrically to the two yokes directly in the guide plane and the guide ways themselves remain unloaded by the mold-closing force. The symmetrical force transmission to the two yokes simultaneously precludes any meandering of the mold halves from their calibrated positions and the fixed closed position since any closing force deformations act equally upon both yokes and are fully symmetrically in the synchronization of the movements of the two yokes.
Since lever-type force-transmission mechanisms are completely eliminated, the construction of the closing unit is substantially simpler than conventional mold closers of the type described. The entire assembly is significantly lighter since the masses of the tension or draw rods and the pressure rods which hitherto were required to couple the yokes can be eliminated.
Still another advantage of this system is that the reduction in the mass which must be moved, by comparison with earlier mold closers, enables the moving parts to be accelerated and decelerated more uniformly and rapidly, thereby reducing the inertia effect upon the synchronization of the mold closer.
According to a feature of the invention a guide beam is provided which traverses the two yokes and through which a tension or traction rod extends which, at one end bears directly upon the distal yoke while the force-generating units, which engage the other end of the traction rod, is received in a slide which acts directly on the proximal yoke, the traction rod applying its force fully symmetrically to the rear yoke. The forces applied to the two yokes are identical and opposite along the aforementioned beam. When the force-generating unit or actuator is a hydraulic or pneumatic cylinder, the traction rod can form a piston rod of this cylinder.
In that case, the one end of the piston rod is fixed to one of the yokes and the slide bears upon the proximal yoke. The piston rod is concentrically surrounded by the guide beam which is carried by the slide. The cylinder is mounted on the slide.
According to a feature of the invention, the mold halves are carried on upwardly-extending projecting or cantilevered portions of the respective yoke, i.e. on respective upwardly extending yoke arms lying above the guide beam while each yoke is also provided with a downwardly-extending or lower cantilevered yoke arm. Between the downwardly-extending or lower yoke arm, an adjustable stop is provided which fixes the two yoke arms in the closed position of the mold. The stop is preferably provided on a further beam which is formed with a synchronizing rod which can be fixed in one of the lower yoke arms. The free end of the synchronizing rod, i.e. the end which is not fixed in one of the yoke arms, can engage a synchronizing drive, for example, a pinion which can mesh with a rack of the closing slide. The pinion may also mesh with a rack of the further or synchronizing rod.
The stop can be provided with adjustments enabling the setting of the closing position, e.g. via a screw thread connection. The adjusta
Davis Robert
Dubno Herbert
Fischer--W. Muller Blasformtechnik GmbH
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