“GUILLOTINE SHUT-OFF VALVE FOR INJECTION MOULDING”

Description

DESCRIPTION The invention relates to a guillotine gate valve for controlling a flow of molten material during injection molding. It is known to control the flow of molten material exiting a gate into a mold cavity using a stem (pin or shutter) that moves linearly back and forth in unison with the flow of molten material. However, the presence and alternating movement of the stem increases flow disturbances, creating areas of material accumulation and stagnation. For example, changing the color of the injected material requires multiple purge injections, resulting in significant material waste. Oblique stems, such as those in EP520345, have the defect of pushing the material against the internal surface of the channel, compressing it further until it reaches the exit. This crushing effect causes defects to appear on the final part. To try to solve the problem, the stem shutter was replaced with a slide valve located near the material exit gate. This solution, adopted for the simultaneous opening and closing of multiple injectors placed in line and controlled by a single actuator, is shown, for example, in EP1409222 (fig. 13). However, a single moving slide valve causes the material to be crushed towards the perimeter of the gate, which is at a lower temperature, thus causing defects in the molded product. WQ2024095073 demonstrates a better solution, using a rotor to control the shutter elements. The system in WQ2024095073 can also be improved. The main purpose of the invention, defined in the attached claims where the dependent claims define advantageous variants, is to improve this state of the art. A particular aim is to improve the actuation of the moving shutter parts. At least one object is achieved by a shut-off valve for controlling a flow of molten material exiting an injection gate into a mold cavity, the valve comprising: • a channel for the molten material, which extends along a first axis up to the gate, • a shutter mounted movably and in such a way that a free end of the shutter can move towards, and reach, a point inside the channel to throttle and / or close the channel thus regulating said flow, • a rotating element placed in proximity to the gate, Ing. Massimiliano Citron (Registered in the Register 1215B) where a portion of the shutter is coupled, in particular directly, to the rotating element so that a rotation of the rotating element causes a movement of the shutter from and / or towards said point, in particular so that a rotation of the rotating element, even partial, causes a progressive movement, proportional to said rotation, of the shutter, where the rotating element comprises a profile (e.g. eccentric or a cam) to which said portion of the shutter is slidably coupled, and the profile has a development such as to convert a rotation of the rotating element of a certain angle into an alternating movement of the shutter in two opposite directions of translation. This structure allows for a specific multiplication or reduction ratio between the rotation of the swivel element and the movement of the shutter for each direction of shutter advance. Specifically, by appropriately designing this profile, it is possible to create independent and different shutter speed profiles during the gate closing and opening phases. By varying the multiplication / reduction ratio of the kinematics, by appropriately sizing the profile or the eccentric or the cam, it is possible to favour greater speed at the expense of force in a certain section of the shutter movement stroke, and in another section of the same stroke it is possible to exert greater force on the shutter at the expense of speed, for example in the gate closing phase. With the above solution, a self-locking mechanism can be implemented, meaning that with little effort applied to the rotating element, the shutter closes with high force, effectively counteracting the pressure of the plastic that tends to reopen the gate. In a preferred embodiment the shutter is movably mounted along a respective second axis (orthogonal or inclined at an acute or obtuse angle with respect to the first axis) and said movement is a translation along the second axis. In a preferred embodiment, said profile comprises a first and a second curved portion, which are for example adjacent, configured so that the first curved portion imposes a displacement or translation on the shutter in one direction and the second curved portion imposes a displacement or translation on the shutter in the opposite direction. Engineer Massimiliano Citron (registered in Roll 1215B) In a preferred embodiment, of simple structure, this profile belongs to a protruding element or fin of the rotatable element or to a recess or groove made in the rotatable element. In a more preferred embodiment, said element or fin protrudes from the perimeter of the rotatable element. In a more preferred embodiment, said recess or groove is formed in the perimeter of the rotatable element or in a peripheral annular zone of the rotatable element. In a preferred embodiment, the rotatable element has an axis of rotation parallel, and in particular coinciding, with the first axis. In a preferred embodiment, the shutter comprises a recess or pin slidably coupled with said profile. In a preferred embodiment, the shutter has the shape of a stem, e.g., linear. Specifically, the stem is free at one end and coupled to the actuator at the opposite end. The advantages of the invention will be made even clearer by the following description of a preferred actuator, in which • Fig. 1 shows a sectional view of a shut-off valve and an actuating device; • Fig. 2 shows a three-dimensional view of assembled valve components; • Fig. 3 shows a three-dimensional view of the components of fig. 2 in exploded view. In the figures, equal elements are indicated by equal numbers, and to avoid crowding the drawings, sometimes only some elements are numbered. Referring to Figure 1, the end 18 of a known injector 10 used to inject molten material into a mold cavity 12 is shown. The injector 10 is usually mounted inside one or more plates 500 that make up the mold and is attached to a known manifold for distributing the molten material (the so-called manifold, also mounted between the plates 500, not shown). The injector 10 includes – and defines – an axial cavity 16 that extends longitudinally along a central axis Y (which preferably is also the axis of polar symmetry for the injector 10). The end 18 of the injector 10 rests on a mold insert 20 with an orifice that defines a gate 98, and the molten material can flow into the cavity 16 up to the gate 98. Overall, the construction of the injector 10 is known and does not need to be repeated. Unlike the known injectors, there is no stem shutter in cavity 16 Ing. Massimiliano Citron (Registration 1215B) (valve pin) arranged in correspondence with the Y axis. The system for regulating the flow of molten material passing through gate 98 is illustrated in detail in fig. 2 and 3. In a tunnel 30 of the insert 20, or of another plate 22 connected to it, a shutter 32 is installed in the form of a linear stem 34 which at one end 36 is free and at the opposite end 38 is coupled to an actuator means 100, an example of which is shown in fig. 2 and 3. The tunnel 30 and the shutter 32 preferably have a complementary shape. The end 38 is engaged in a curved fin 50 formed in relief on the perimeter of a disk 52 rotatably mounted around the gate 98. The fin 50 is inserted in a corresponding notch 40 present at the end 38 and, like a cam, has the function of determining with its profile / shape the space / time trend (speed) for the shutter 32. A preferred embodiment for the fin 50 is shown in greater detail in Fig. 3. The fin 50 is formed by three curved and connected portions, namely a central portion 72 and two terminal portions 70, 74 (illustrated symmetrically but not necessarily). The central portion 72 has a concavity facing outwards from the disc 52 and determines the closed position of the shutter 32. The terminal portions 70, 74 have a concavity facing the Y2 axis and determine the open position of the shutter 32. The disc 52 preferably has an external toothing 54 that engages a toothing 56 on a shaft 58 that can be moved back and forth along an axis W2. By moving the shaft 58 (with any known drive), the disc 52 can be rotated around an axis Y2 parallel to - and preferably coinciding with - the Y axis, and consequently the fin 50 can be angularly moved with respect to the shutter 32. The fin 50 thus interacts with the groove 40 and pushes the shutter 32 back and forth. The profile shape of the fin 50 determines the movement dynamics for the shutter 32. By pushing the end 38 back and forth, a proportional sliding of the shutter 32 inside the tunnel 30 is obtained, which results in the greater or lesser protrusion of the end 36 inside the channel of the gate 98. This protrusion determines the degree of closure of the gate 98, from totally open to totally closed (or vice versa). Intermediate positions for the shutter 32 are possible. The particular shape of the fin 50 allows the shutter 32 to be moved back and forth without changing the direction of rotation of the disk 52. For example, when the notch 40 slides from the terminal portion 70 towards the central portion 72, the shutter 32 closes the gate 98, Ing. Massimiliano Citron (Registration 1215B) when the notch 40 slides from the central portion 72 towards the terminal portion 74 the shutter 32 opens the gate 98. The same happens if the disk 52 rotates in the opposite direction. The variant of fig. 2 and 3 shows a disk 52 with two fins 50 in diametrically opposed positions to drive two shutters 32 back and forth with the same function described above and along the same Z axis. It is also possible to drive a single shutter 32, or more than two by adding respective fins 50 to the disk 52. In the example, the angle between the Z axis and the Y axis is right, but not necessarily: it could be acute or obtuse. In fact, it is sufficient to orient the actuator means 100 or the Z axis differently to obtain inclined trajectories of a shutter 32. For example, three or more shutters 32 could be arranged like the edges of a regular pyramid having its axis coinciding with the Y axis. The raised lug 50 can be replaced by a corresponding groove on the disc 52, while the shutter 32 can engage it, for example, via a pin slidably inserted into it. To rotate the disk 50, other systems other than those illustrated can also be used.

Claims

1. Shut-off valve for controlling a flow of molten material exiting an injection gate towards a mold cavity, comprising: • a channel for the molten material extending along a first axis to the gate, • a shutter movably mounted so that a free end of the shutter can move to and reach a point within the channel to restrict and / or close the channel thereby regulating said flow, • a rotatable member located in proximity to the gate, where a portion of the shutter is coupled to the rotatable member so that a rotation of the rotatable member causes a movement of the shutter to and / or towards said point, so that a rotation of the rotatable member causes a progressive movement of the shutter proportional to said rotation, where the rotatable member comprises a profile to which said portion of the shutter is slidably coupled,and the profile has a development such as to convert a rotation of the rotating element of a certain angle into an alternating movement of the shutter in two opposite directions of movement.

2. Valve according to claim 1, wherein said profile comprises a first and a second curved portion configured so that the first curved portion imposes a displacement on the shutter in one direction and the second curved portion imposes a displacement on the shutter in the opposite direction.

3. A valve according to claim 2, wherein the first curved portion has a convexity facing the axis of rotation of the rotatable element and the second curved portion has a convexity facing in the opposite direction.

4. Valve according to claim 1 or 2 or 3, wherein said profile belongs to a fin protruding from the perimeter of the rotating element.

5. Valve according to claim 1 or 2 or 3 or 4, wherein said profile belongs to a recess or groove obtained in the perimeter of the rotating element.

6. Valve according to any preceding claim, wherein the rotatable element has an axis of rotation parallel to, and in particular coinciding with, the first axis.

7. Valve according to any preceding claim, wherein the shutter comprises a recess or pin slidably coupled with said profile.

8. Valve according to any preceding claim, wherein the shutter has the shape of a stem.

9. Valve according to claim 8, wherein the stem has a free end and at the opposite end is coupled to the profile.

10. Valve according to any preceding claim, wherein said 5 displacement is a linear translation of the valve along a second axis.