Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Mold motion or position control
Reexamination Certificate
1998-04-28
2001-04-03
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Mold motion or position control
C425S451900, C425S589000, C425S595000
Reexamination Certificate
active
06210144
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a closing unit for an injection molding machine.
2. Related Art
The closing unit of an injection molding machine receives the injection mold. It carries out the movements necessary for the closing and opening of the injection mold and produces the forces necessary for the locking and opening of the injection mold. The main components of each closing unit are a stationary plate on the injection side (hereinafter referred to as the injection plate), a movable closure plate, as well as a locking device. One part of the injection mold is clamped on the stationary injection plate while the complementary part of the injection mold is clamped on the movable closure plate. By locking device there is to be understood the device which, upon the injection and further pressing, produces the necessary closing force for keeping the injection mold closed.
Both mechanical locking devices with lever mechanisms and hydraulic locking devices with hydraulic cylinders are known.
The present invention relates to a closing unit with hydraulic locking. In the book “Kunstsfoff-Maschinen-Führer,” 3rd edition, edited by Dr. Eng. Friedrich Johannabe, published by Carl Hanser Verlag (Munich, Vienna), 1992 various constructions of closing units with hydraulic locking are described.
In most closing units with hydraulic locking, a force cylinder is developed as a pressure cushion and is arranged on a support plate behind the movable closure plate.
From FIG. 56, page 110, of said book, a closing unit having four hydraulic cylinders on the stationary injection plate is, however, known. The pistons of these hydraulic cylinders are connected rigidly via connecting rods with the movable closure plate. The four hydraulic cylinders produce the required closing force but also, at the same time, carry out the opening and closing movements of the movable closure plate. Since the four hydraulic cylinders at the same time perform a locking function and a displacement function, they must be both of large cross section and have a large stroke and they therefore take up a relatively large amount of space. The four relatively large hydraulic cylinders accordingly substantially impede access to the injection unit and furthermore have a very high consumption of oil. The structural length of the closing unit is substantially greater than the greatest possible distance between the injection plate and the closure plate.
From FIG. 53B, page 108, of the same book, a more compact closing unit, also having four hydraulic cylinders on the stationary injection plate, is known. The four connecting rods are detachably connected by claws at their ends to the corresponding hydraulic cylinder. Opening and closing movements are produced, with connecting rods uncoupled, by high-speed cylinders arranged on the side. The stroke of the four hydraulic cylinders in this construction must accordingly correspond merely to the difference in length between the largest and smallest injection molds. This construction is primarily of interest when the injection molds used all have more or less the same length. If the closing unit, however, is to be used with injection molds of different length, the stroke of the hydraulic cylinders must be relatively large and the closing unit of FIG. 53B has substantially the same disadvantages as the aforementioned closing unit of FIG. 56.
The object of the present invention is to create a compact closing unit which is suitable for injection molds of different length. The object is achieved by a closing unit in accordance with claim
1
.
SUMMARY OF THE INVENTION
The closing unit of the invention comprises, in known manner, a fixed injection plate with injection opening and a movable closure plate, these plates forming, for instance, clamping plates for an injection mold. A displacement device for the movable closure plate produces the opening and closing movements and makes it possible to position the movable closure plate relative to the fixed injection plate. Several hydraulic force cylinders, preferably four, are arranged on the stationary injection plate and produce the closing force. This closing force is transmitted by connecting rods, each of which is connected mechanically with the piston of a force cylinder to the movable closure plate. The closing unit of the invention differs from the known closing unit, which has the features indicated above, primarily by the fact that the connecting rods are turnable around their longitudinal axes into a first and a second angular position, first locking means being arranged along a rod section A on the connecting rods and second locking means being arranged on the movable closure plate, and these first and second locking means being developed complementary to each other in such a manner that in the first angular position of the connecting rods they make and axial displacement of the movable closure plate relative to the connecting rods possible and that in the second angular position of the connecting rods the first locking means in the rod section A on the connecting rods cooperate with the second locking means on the movable closure plate to transmit the necessary closing force.
The closing unit of the invention permits an extremely compact, space-saving construction. The required stroke of the force cylinders and thus their outside dimensions are minimum. As compared with known closing units, the closing unit of the invention is characterized by a very small structural length. The structural length of the closing unit need in fact not be substantially larger than the greatest possible distance between the injection plate and the closure plate. The hydraulic connections for the force cylinders and the displacement device of the closure plate can be arranged on the fixed injection plate. Flexible hydraulic connections are, accordingly, not required. Therefore the closing unit is excellently suited for receiving injection molds of different length. The range of length of the injection molds is limited here solely and exclusively by the length of the rod section A having the first locking means.
The first locking means advantageously comprise an outer toothing on the connecting rod, and the second locking means comprise a locking bushing which is fastened fixed for rotation on the movable closure plate and has an inner toothing. Inner toothing and outer toothing are divided by longitudinal grooves into at least two rows of teeth. In the first angular position, the rows of teeth of the outer toothing can be passed through axially by longitudinal grooves of the inner toothing and the rows of teeth of the inner toothing can be passed through axially by the longitudinal grooves of the other toothing, so that an axial displacement of the movable closure plate relative to the connecting rods can take place. In the second angular position, the teeth of the inner toothing, on the other hand, can engage behind the teeth of the outer toothing for the transmission of a pulling force.
The teeth of the inner and outer toothings can be arranged annularly or helically. In order to assure a dependable engagement of the outer toothing in the inner toothing, a substantially axial flank clearance should be developed between inner and outer toothings. A large flank clearance, however, also has substantial disadvantages. Thus, for example, the operating stroke of the force cylinders is increased thereby, and thus the consumption of energy by the closing unit. The flows through the force cylinders are considerably greater so that the hydraulic system of the closing unit must also be made larger. Furthermore, the unlocked connecting rods are relatively strongly accelerated upon overcoming a large flank clearance, so that the teeth of the inner toothing strike with great force against the teeth Of the outer toothing.
Within the scope of this invention, however, there is proposed an extremely simple and inexpensive solution which completely eliminates the disadvantages of a large axial flank clearance. This so
Mailliet Marc
Mailliet Monique
Mailliet Pierre
Fitzpatrick ,Cella, Harper & Scinto
Husky Injection Molding Systems Ltd.
Mackey James P.
Mailliet Marc
Mailliet Monique
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