“VALVE AND GUILLOTINE SHUTTERING METHOD FOR INJECTION MOULDING”

Description

“Valve and guillotine shut-off method for injection molding” on behalf of INglass Spa with headquarters in S. Polo di Piave (TV) Designated Inventors: Massimo Rossi, Alessandro Dario DESCRIPTION 5 The invention relates to a valve and guillotine closing method for control a flow of molten material during injection molding. It is known to control the flow of molten material exiting a gate into a cavity. mold by means of a stem (pin or shutter) which is linearly movable back and forth with movement consistent with the flow of the molten material. The presence and movement 10 alternating of the stem however increases the disturbances on the flow creating accumulation zones and stagnation of the material, so much so that for example the operation of changing the color of the material injected requires multiple purge injections with significant waste of material. Oblique stems as in EP520345 have the defect of pushing the material against the internal surface of the canal, compressing it further until the exit. This effect 15 of crushing causes the appearance of defects on the final piece. To try to solve the problem, the stem shutter has been replaced by a slide valve placed at the material output gate. This solution, adopted for the simultaneous control of opening and closing of multiple injectors placed in line and controlled by a single actuator, is e.g. shown in EP1409222 (fig. 13). However, a single movable guillotine involves the 20 crushing of the material towards the perimeter of the gate orifice, which is located at a lower temperature, thus causing defects in the printed product. A better solution, as in EP1064138, is to use two opposing guillotines which have the closing point in the centre of the channel, because the temperature is higher there. EP1064138 however provides two planar guillotines operated by a single actuator 25 placed on the far perimeter of the mold, with considerable complications in the movement and imprecise control of the position of the guillotines. Complex and installation is also expensive due to the proximity of the guillotines to the gate (orifice of exit of the plastic material) and therefore to the cavity of the mould, requires small thicknesses of containment of the same therefore very resistant and expensive materials. However, despite 30 efforts, the impossibility of eliminating the witness (small protuberance in the shape of a cylinder) that this solution leaves on the printed piece. Main object of the invention, defined in the attached claims where those employees define advantageous variants, is to improve this state of the art. A particular aim is to improve the actuation of the moving shutter parts. Another particular purpose is to improve the performance and / or characteristics of an injector (or nozzle) for injection molding. At least one purpose is achieved by a method of moving a shutter element mounted in a shut-off valve designed to control a flow of molten material 5 exiting from the gate of an injector towards a mold cavity, the valve comprising a channel for the molten material extending along a first axis to the gate, where the shutter element has a first free end and is mounted movably for move along a second axis so as to get closer to the first axis so that the first 10 free end can move and reach a point inside the channel to strangle the channel and limit said flow, where the shutter element is coupled to a portion of material having volume deformable by the piezoelectric effect, and the said portion of material is electrically stimulated to make it shrink and / or dilate 15 so as to transfer translational movement to the shutter element. Another aspect of the invention relates to a shut-off valve for controlling a flow of molten material exiting the gate of an injector towards a mold cavity, the valve including: - a channel for the molten material that extends along a first axis to the gate, 20 - a shutter element having a first free end and movably mounted for move along a second axis so as to get closer to the first axis so that the first free end can move and reach a point inside the canal to strangle the channel and limit said flow, - an actuator to translate the shutter element along the second axis, 25 where the actuator includes a portion of material that has a volume deformable by the piezoelectric effect, and It can be electrically stimulated to increase and / or decrease its own dimensions, 30 the shutter being coupled to said portion to receive movement therefrom translation along the second axis. The advantage of the invention lies in the fact that the mechanism can be constructed in very compact way and then arranged near the gate, without further delays mechanical with external actuators. Furthermore, the shutter movement can be extremely fast, or at least variously controlled e.g. by an electronic control unit, with all the advantages of a software programming. Furthermore, the force applied to the shutter can be considerable and concentrated in a small space. 5 Another advantage is that the shut-off valve is of mechanical construction simple, low maintenance, long lasting and not very sensitive to environmental contamination (dust, etc.) Below are some favorite variations, to be used alone or in combination. The valve preferably includes an electrical power supply system for 10 electrically stimulate said portion of material to make it shrink and / or expand. Preferably two or more shutter elements are connected to the same actuator. Preferably the valve comprises two or more said actuators, each coupled to at least one shutter element. Preferably the said actuator is configured to impart linear motion 15 to the shutter element, but also curvilinear motion. Preferably, between the material portion and the shutter element are interposed means of multiplying displacement, e.g. levers, hinges, leverage. In a variant, useful for increasing the stroke of the shutter element, the valve filling comprises a plurality of said portions of material arranged in series, e.g. 20 linearly or in a curve / spiral, to save space on the mold. So the overall displacement imposed on the shutter element is the sum of the individual deformations of each portion of material. In one variant the shutter element is connected to the said portion of material directly so as to obtain a displacement corresponding to that generated by 25 said portion of material. In one variant the displacement imposed on the shutter element by the said portion of material is only in one sense / direction, and preferably in the opposite direction the element shutter is pushed by an elastic element. In one variant the displacement imposed on the shutter element by said portion of 30 material is in two directions, opposite to each other. In one variant the shutter element is installed in a cavity of a plate of the die. In one variant, the shutter element has the shape of a stem, e.g. straight. In particular the shutter element has a free end and the opposite end coupled to a actuator. The actuator is preferably installed in a mold cavity, e.g. a cavity obtained in a plate containing an insert on which the injector rests. In one variant the angle between the sliding axis of the shutter element and the axis of 5 dimensional change of said portion is right. In one variant the same actuator is coupled to two or more shutter elements for move them simultaneously. The advantages of the invention will be made even clearer by the following description of a preferred actuator, in which 10  Fig. 1 shows a cross-sectional diagram of the end of an injector (nozzle);  Fig. 2 shows a partial three-dimensional view of a valve actuator. filling;  Fig. 3 shows a cross-sectional diagram of a second valve actuator. filling; 15  Fig. 4 shows a partial three-dimensional view of a second drive for shut-off valve. In the figure equal elements are indicated by equal numbers, and in order not to crowd the drawings sometimes only some numbers are reported. Referring to figure 1, the end 18 of a known injector 10 used for 20 inject molten material into a mold cavity 12. The injector 10 is usually mounted inside one or more plates 500 that make up the mold and is fixed to a known distribution manifold of the molten material (the so-called manifold, also mounted inside said plates, not shown). The injector 10 comprises an innermost hollow body 14 which defines an axial cavity 16 which is 25 extends longitudinally along a central Y-axis. The Y-axis preferably is also a polar symmetry axis for injector 10. The end 18 of injector 10 rests on a mold insert 20 with an orifice that determines a gate 98, and the molten material can slide into cavity 16 to gate 98. Overall, the injector construction 10 is well known, and there is no need to repeat it. 30 Unlike the known injectors, there is no stem shutter in cavity 16 (valve pin) arranged parallel to the Y-axis. The system for regulating the flow of molten material passing through gate 98 is illustrated in detail in Fig. 2 and following. In a tunnel 30 of the insert 20, or of another plate connected to it, a shutter 32 in the form of a straight stem 34 which is free at one end 36 and at the opposite end 38 is coupled to an actuator 100, an example of which is shown in fig. 2. The tunnel 30 and the shutter 32 preferably have a complementary shape. The actuator 100 is preferably installed in a cavity obtained in a plate which 5 contains insert 20. The actuator 100 is capable of moving the stem 34 by deformation of a material 102 (e.g. a block) having a volume deformable by the piezoelectric effect. The end 38 is connected to a bridge structure 104 integral with the ends of the material 102. 10 By electrically powering the material 102 in an appropriate (and known) way with a electrical tension, it is possible to lengthen or shorten the material 102 along an axis W. This dimensional variation acts at the base of the bridge 104 and is converted into a movement along the Z axis. You can then push end 38 back and forth along the Z axis to get a 15 proportional sliding of the shutter 32 inside the tunnel 30, resulting in the greater or lesser protrusion of the end 36 inside the gate channel 98. This protrusion determines the degree of closure of gate 98. In the example the angle between the Z-axis and the W-axis is right, but not necessarily: it could be sharp or dull. 20 Another example of actuation for the shutter 32 is shown in fig. 3 and 4. Here it is illustrated a variant of the system that allows more than one shutter to be moved at a time, in the example two 32-inch opposing shutters that can move along the same Z-axis. Each shutter 32 is coupled with a respective actuator 100 to be moved independently of the other shutter 32. 25 However, it is possible to move more than two shutters simultaneously. installing more actuators 100. It is also possible to couple more than one shutter 32 to the same actuator 100 so as to move more than one shutter 32 simultaneously. In the examples the angle between the Z-axis and the Y-axis is right, but not necessarily: 30 could be sharp or blunt. In fact, it is sufficient to orient the actuators differently. 100 to obtain inclined trajectories of a shutter 32. E.g. three or more shutters 32 they could be arranged like the edges of a regular pyramid having an axis coinciding with the Y axis. * * *

Claims

1. A method of moving a shut-off element mounted in a shut-off valve for controlling a flow of molten material exiting an injector gate toward a mold cavity, the valve comprising a channel for the molten material extending along a first axis to the gate, the shut-off element having a first free end and being movably mounted to move along a second axis so as to approach the first axis so that the first free end can move and reach a point inside the channel to restrict the channel and limit said flow, the shut-off element being coupled to a portion of material having a volume deformable by the piezoelectric effect, and said portion of material is electrically stimulated to cause it to shrink and / or expand so as to transfer translational motion to the shut-off element.

2. A shut-off valve for controlling a flow of molten material exiting the gate of an injector into a mold cavity, the valve comprising: - a channel for the molten material extending along a first axis to the gate, - a shut-off element having a first free end and movably mounted to move along a second axis so as to approach the first axis so that the first free end can move and reach a point within the channel to restrict the channel and limit said flow, - an actuator for translating the shut-off element along the second axis, the actuator comprising a portion of material having a volume deformable by the piezoelectric effect, and which can be electrically stimulated to increase and / or decrease its size, the shut-off being coupled to said portion to receive translational motion therefrom along the second axis.

3. A valve according to claim 2, comprising an electrical power system for electrically stimulating said portion of material to shrink and / or expand.

4. Valve according to any preceding claim, comprising two or more shutter elements connected to the same actuator. Eng. Massimiliano Citron (Registration 1215B) 5. Valve according to any preceding claim, comprising two or more said actuators, each coupled to at least one shutter element.

6. Valve according to any preceding claim, wherein displacement multiplication means are interposed between the material portion and the shutter element.

7. Valve according to any preceding claim, comprising a plurality of said portions of material arranged in series so that the overall displacement imposed on the shutter element is the sum of the individual deformations of each portion of material.

8. A valve according to any preceding claim, wherein the displacement imposed on the shutter element by said portion of material is only in one direction, the valve comprising an elastic element for moving the shutter element in the opposite direction.

9. A valve according to any preceding claim, wherein each or the shutter element is installed in a cavity of a mold plate.

10. A valve according to any preceding claim, wherein the or each actuator is installed in a mold cavity.