Patent Description:
It is well known to control the flow of molten material exiting a nozzle towards a mold cavity via a stem (pin) that is linearly movable back and forth. However, the presence and alternating movement of the stem increases flow perturbations by creating areas of buildup and stagnation of material, so much so that, e.g., the operation of changing the color of the injected material requires multiple purge injections with substantial waste of material. Oblique stems as in <CIT> have the defect of pushing the material against the inner surface of the channel, further compressing it up to the outlet. This squeezing effect causes defects to appear on the final piece.

In an attempt to solve the problem, the stem shutter was replaced by a guillotine valve placed in the nozzle area. This solution, adopted for the simultaneous opening and closing control of multiple injectors placed in line and controlled by a single actuator, is e.g. disclosed in <CIT> (Fig. <NUM>). However, a single movable guillotine results in squashing of the material toward the nozzle perimeter, which is at a lower temperature, thus causing defects in the molded product.

A better solution, as in <CIT>, is to use two opposing guillotines that have the closing point at the center of the channel, because there the temperature is higher. <CIT>, however, envisages two planar guillotines driven by a single actuator located on the distant perimeter of the mold, with considerable complications in the actuation, and imprecise control, of the position of the guillotines.

<CIT>, <CIT>, document XP001248640 (ISSN: <NUM>-<NUM>) and <CIT> disclose actuation systems for a gate vale.

The main object of the invention, defined in the attached claims in which the dependent ones define advantageous variants, is to improve this state of the art.

Particular object is to improve the actuation of the movable obturating parts.

At least one object is achieved by an obturation valve for controlling a flow of molten material exiting a nozzle toward a mold cavity, comprising:.

The above valve has several advantages because it allows:.

The actuation system for the valve obturating members is irrespective of the number and configuration of obturating members, which advantageously can be more than one.

Said point inside the channel, which is the destination of the free end of the obturating member, may be a point at the center of the channel (i.e. near the axis of the channel), a point at the periphery of the channel (i.e. near the walls of the channel, offset from the axis of the channel), or a point intermediate to the previous two conditions.

In a compact preferred variant, the rotatable member extends around (and e.g. also surrounds) the first axis and the channel; specifically, the rotatable member comprises a ring that surrounds the first axis and the channel.

The rotatable member is rotatably mounted on a fixed (i.e. stationary) member that.

Thus the fixed member can be quickly inserted into a seat of a plate of the mold and easily removed for maintenance.

In a preferred variant, the rotatable member comprises a profile (e.g. eccentric or a cam) to which said portion of the obturating member is slidingly coupled, the profile having a development that converts a rotation of the rotatable member into a translation of the obturating member along the second axis. For example, the profile has.

In a preferred variation, the rotatable member comprises a ring or crown coaxial to the first axis (and e.g. also to said fixed member), and e.g. said profile is a groove or fin or cam formed in relief in the crown or ring. In order to move the obturating member, the groove or fin may have an increasing height or depth along its length, and/or a distance from the rotation axis of the rotatable member that varies along the length of the profile. The conformation of the groove or cam determines the width of the stroke of a or each obturating member.

In a preferred variant, the rotatable member has a rotation axis that is.

In a preferred variant, the valve comprises two or more obturating members whose respective second axes are coplanar and arranged.

In a preferred variant, the valve comprises only two obturating members movable along the sides of an angle with a vertex at said point, wherein the lying plane of the angle is orthogonal to, or passing through, the first axis.

In the case of two or more obturating members said point becomes a common convergence point, or a point of channel closure, for the translation of the obturating members (and for the second axes).

In a preferred variant, the valve comprises three or more obturating members and their respective second axes are arranged like the edges of an imaginary pyramid, said convergence point forming the apex of the pyramid. In a more preferred variant, said imaginary pyramid is arranged so that its base intersects the first axis and the channel, more specifically so that it is orthogonal to the first axis.

In a preferred variant, which improves the injector performance, the valve comprises two or more obturating members that are actuated by the rotatable member and mounted.

The above configuration of the obturating members (positioned obliquely to the axis of the injector) has several advantages:.

An improvement in the injector performance occurs when the valve comprises.

The use of three or more obturating members makes it possible to better balance the forces acting on them and/or the rotatable member, and to limit or avoid abnormal wear of the rotatable member. If e.g. an obturating member, due to excessive and unexpected stress, malfunctions, the residual stress is distributed over at least two other obturating members, reducing the possibility of an overall malfunction of the valve.

With three or more cooperating obturating members any temporary irregularity is therefore less likely to block the molding process, and the valve would continue to operate leading to a new equilibrium condition.

The use of three obturating members results in an excellent compromise.

In particular, it is advantageous for all the obturating members to be connected to the rotatable member. In this case, note that the rotatable member acts as a means for synchronizing the movement of the obturating members toward and from said point.

In particular, said acute angle is equal for all the second axes of the obturating members.

In a preferred variant, the valve comprises an elastic means adapted to generate a force to push a or each obturating member toward or away from said convergence point.

In a preferred variant, the valve comprises a drive adapted to rotate the rotatable member by a predetermined (and/or programmable) angle. In a more preferred variant, the drive comprises an actuator with a linearly translatable arm, the arm being connected to the rotatable member so as to convert a thrust and/or a pull of the arm into a rotation of the rotatable member.

In a preferred variant, the drive comprises an actuator with a rotary shaft, wherein the shaft is connected to the rotatable member so as to convert a rotation of the shaft into a rotation of the rotatable member, or
comprises a nut-screw that meshes with a toothing provided on the rotatable member, so that a rotation of the nut-screw is converted into a rotation of the rotatable member, or comprises a gear that meshes with a toothed crown of the rotatable member, so that a rotation of the shaft transfers rotary motion to the rotatable member.

In a preferred variant, the valve comprises a sensor (e.g. a rotary encoder or a potentiometer or a microswitch) adapted to detect an angular stroke of the rotatable member.

The valve in a preferred variant comprises an end-of-travel sensor (e.g. microswitches or linear/angular position encoders) to control the opening/closing position and/or intermediate positions of a or each obturating member. The end-of-travel sensor may be installed to detect the position of one or each obturating member and/or the angular position of the rotatable member and/or an actuating organ of the actuator or component thereof (e.g. said arm or said rotary shaft, or a gear or other).

In a more preferred variant, the valve comprises an electronic circuit that is connected to one or each of said sensor for reading a signal therefrom and connected to the drive to drive its operation. Specifically, the electronic circuit is configured (and/or programmed) to implement an angular position feedback control on the rotatable member via the sensor and the drive.

Another aspect of the invention relates to a system of two or more valves, each valve being defined as above, wherein the rotatable members of each valve are connected to each other so that they can be operated synchronously, particularly by a same single actuator.

Preferably, the rotatable members of two valves or all the valves form or make up a kinematic chain that connects the rotatable members. More preferably, the rotatable members of two valves are connected to each other by an idle gear, or the rotatable members of all the valves are connected to a common driving organ.

One or each obturating member may also roto-translate (or translate on itself) during its movement to and/or from said point. More particularly, a portion of the obturating member, or said coupled portion of the obturating member, is connected to the rotatable member so that a rotation of the rotatable member entails a translation of the obturating member along the second axis and also a rotation of the obturating member to and/or from said point. More specifically, the rotation of the obturating member occurs about said second axis.

The advantages of the invention will be even clearer from the following description of a preferred actuator, in which.

In the figures equal elements are indicated by equal numbers, and to avoid crowding the drawings sometimes only some elements are numbered.

<FIG> partially shows a mold MC comprising an injector <NUM> that is enclosed within mold plates <NUM>, <NUM> clamped against each other. The injector <NUM> is connected to a known manifold <NUM> to receive molten material and convey it via a channel <NUM> to a nozzle <NUM> from which it is injected inside a mold cavity <NUM>.

At the nozzle <NUM>, the channel <NUM> extends linearly along an X axis and can be throttled by an occlusion valve <NUM>.

The valve <NUM> comprises a cylinder or torus shaped body <NUM> that is fixed on the plate <NUM> and faces the cavity <NUM>. The body <NUM> has a central pass-through cavity <NUM> in which the nozzle tip <NUM> and the end of the injector <NUM> are located. The nozzle tip <NUM> abuts internally against the body <NUM>, which has a surface <NUM> that participates in making up the mold cavity. Optionally and advantageously, the surface <NUM> can be variously shaped or, at the bottom of the body <NUM>, a shaped plate or member can be added. The X axis coincides with the axis of the body <NUM>.

In seats provided inside the body <NUM>, are slidably mounted obturating members <NUM>, e.g. three. Specifically, the obturating members <NUM> are all equal and/or made e.g. as pins or lamellae (see also <FIG>) having circular or polygonal cross-sections, but not necessarily.

The obturating members <NUM> are arranged along the edges of an imaginary regular triangular-base pyramid and converge toward a convergence point P located along the X-axis and in the center of the channel <NUM> near the outlet of the channel <NUM> inside the cavity <NUM>. The imaginary pyramid has a base orthogonal to the X axis.

The arrangement of the obturating members <NUM> allows them to slide linearly toward the point P until their tips <NUM>, properly shaped, touch. As the obturating members <NUM> approach the convergence point P, they form a bulkhead that gradually closes the channel <NUM>. When the tips <NUM> join at the point P, the channel <NUM> is completely closed and the molten material can no longer pass through the nozzle <NUM> toward the cavity <NUM>.

An annular-shaped rotatable member <NUM> (see also <FIG>) is mounted coaxially on the body <NUM> so that it can rotate about the X axis with respect to the body <NUM>. The surface of the rotatable member <NUM> facing the cavity <NUM> (the surface opposite the plates <NUM>, <NUM>) has three profiles <NUM>, e.g. fins in relief, having a longitudinal development that follows a spiral arc converging toward the center of the rotatable member <NUM> (i.e. toward the X axis). The profiles <NUM> are arranged with polar symmetry around the X axis.

The obturating members <NUM> are arranged along radii originating from the center of the rotatable member <NUM>, such center coinciding with the point P. The end of each obturator <NUM> opposite the tip <NUM> has a recess <NUM>, e.g. a notch, complementary to the thickness or outline of the profiles <NUM>. Each recess <NUM> is snugly slidingly mounted astride a respective profile <NUM>. In the figures, as examples, the recesses <NUM> and the profiles <NUM> are rectangular in cross-section.

It follows that a rotation of the rotatable member <NUM> results in the progressive relative sliding of the profiles <NUM> within the recesses <NUM>, and the decreasing distance from the X axis of the edges of the profiles <NUM> progressively pushes the obturators <NUM> toward the point P, i.e. toward the center of the channel <NUM> (closure of the nozzle <NUM>). A rotation of the rotatable member <NUM> in the opposite direction results in the retrogression of the obturators <NUM> away from the point P (opening of the nozzle <NUM>).

Then the degree of occlusion of the channel <NUM> can be controlled by controlling the angular stroke of the rotatable member <NUM>.

Preferably, the profiles <NUM> are all equal so that each obturating member <NUM> is transmitted the same motion dynamics and the obturating members <NUM> can be moved synchronously. If necessary, the profiles may be different from each other.

Various means and actuators (electrical, pneumatic, or hydraulic types) can be used to set the rotatable member <NUM> into rotation.

A preferred embodiment envisages the rotatable member <NUM> having a radial slot <NUM> into which the head <NUM> of an arm <NUM> is insertable. The head <NUM> is pivoted in the radial slot <NUM> about an axis parallel to the X axis by a pin <NUM>, and the arm <NUM> is arranged approximately along a straight line tangent to the perimeter of the rotatable member <NUM>. The arm <NUM> is slidable back and forth (see arrow F in <FIG>), moved e.g. by an electric motor or a pneumatic or hydraulic actuator. The reciprocating movement of the arm <NUM> forces the rotation of the rotatable member <NUM> in two opposite directions.

A different preferred embodiment (<FIG>) envisages the rotatable member <NUM> having an outer toothing <NUM> on which is engaged a rack <NUM> provided on the arm <NUM>. Again, the reciprocating linear motion of the arm <NUM> imposes the rotation of the rotatable member <NUM> in two opposite directions.

A different preferred embodiment (<FIG>) involves the rotatable member <NUM> having an external toothing <NUM>, which meshes with a thread <NUM> provided on the head <NUM> of a rotating shaft <NUM>. The rotary motion of the shaft <NUM> forces the rotation of the rotatable member <NUM> in two opposite directions.

A different preferred embodiment (<FIG>) envisages the rotatable member <NUM> having the outer toothing <NUM> meshing with a gear/pinion <NUM> driven into rotation by, for example, an electric motor or a rack (analogous to the rack <NUM>). Then, the rotary motion of the pinion <NUM> can force the rotation of the rotatable member <NUM> in two opposite directions. The gear <NUM>, the thread <NUM> and the rack <NUM> make up a kinematic chain of transmission and transformation of the linear or rotary motion provided by the actuator. The kinematic chain can vary/modify the number of revolutions and torque supplied to the rotatable member <NUM>.

The shape of the obturating members <NUM> may vary from what is illustrated. In particular, the base of said imaginary pyramid may be any polygon, and the geometric choice of the pyramid defines the position and number of the obturating members <NUM>.

There can also be only two movable obturating members <NUM> along the sides of an angle with vertex at the point P, wherein the lying plane of the angle may be orthogonal to the X axis or passing through the X axis. There can also be only one obturating member <NUM>, in which case the point P does not lie along the X axis but is shifted to the perimeter edge of the channel <NUM>. The directions in which the obturators <NUM> move may also vary from what has been illustrated. In particular, a different preferred embodiment is that the obturators <NUM> all move along one and the same plane, that is, they are arranged to slide along the diagonals of a regular polygon (the point P then being the barycenter of the polygon); or, if there are two obturators <NUM>, along one and the same line.

In preferred variants, the valve <NUM> comprises:.

In a more preferred variant, one or each obturating member <NUM> comprises a local-heating device <NUM>.

In a preferred variant that favors compactness, two or more valves <NUM> may be controlled by a single drive. in <FIG> the gear <NUM> could be connected to several toothings <NUM> of different valves <NUM>. Or (<FIG>) between various toothings <NUM> of different members <NUM> an idle gear <NUM> could be placed to transfer rotary motion from one valve <NUM> to another, so as to form a kinematic chain comprising all members <NUM>. In <FIG> motion could be imparted to any of the gears <NUM> or to any of the members <NUM>.

The transmission of rotary motion through a cascade of gears instead of lever linkages improves the precision of the system.

The nozzle may be of the circular type or with different cross-section, such as rectangular or other polygonal shape.

Claim 1:
Obturation valve (<NUM>) for controlling a flow of molten material exiting a nozzle (<NUM>) towards a mold cavity (<NUM>), comprising:
• a channel (<NUM>), for the molten material, which extends along a first axis (X),
• an obturating member (<NUM>) mounted
- movably along a respective second axis, and
- so that a free end of the obturating member (<NUM>) can move towards, and reach, a point (P) inside the channel (<NUM>) to throttle the channel (<NUM>) thereby regulating said flow,
• a rotatable member (<NUM>) placed in proximity of the nozzle (<NUM>),
wherein a portion (<NUM>) of the obturating member (<NUM>) is coupled to the rotatable member (<NUM>) so that a rotation of the rotatable member entails a translation of the obturating member (<NUM>) along the second axis from and/or towards said point (P),
characterized in that
the rotatable member (<NUM>) is rotatably mounted on a stationary member (<NUM>) which
is mounted on a mold plate (<NUM>) having a seat, and
comprises a surface (<NUM>) that forms a portion of the mold cavity (<NUM>),
the stationary member (<NUM>) being inserted into the seat.