Device to adjust the linear position of a shutter

A device is described for adjusting the linear position of one or more shutters (20) in an injection moulding system. The device comprises a body, comprising a cavity in which there can axially slide a movable element, and an adjustment element for adjustment of the axial position of the body with respect to a plate. The adjustment element is rotatably mounted between the body and the plate and comprises a threaded portion on which a corresponding thread of the body and/or of the plate is engaged.

The invention relates to a device to adjust the linear position of a shutter in an injection molding system.

Known injection molding systems typically use a hydraulic, pneumatic or electric device to adjust one or more shutters regulating the flow of molten material towards one or more cavities of the mold. The device has for this purpose a piston movable inside an outer casing fixed to a hot runner, to a mold plate, or to another support element.

A recent device is described in EP 3003681.

It includes a fixed upper mounting plate and an adjustment screw or threaded ring to change the axial position of the shutter. The threaded ring is screwed inside the mounting plate and by screwing it clockwise and counter-clockwise it can be moved axially. Then with a screw an interconnection is created between the adjustment threaded ring and a body that contains a movable element connected to the shutter, thus determining an end stroke for the shutter itself.

This solution has disadvantages, because there may be adjustment errors due to the intrinsic need of screwing consecutively two threaded elements in series, which introduces tolerance and thermal expansion problems. Furthermore, the interconnection screw is small in size, and could give problems during maintenance (gripping).

The main object of the invention is to remedy one or more of the aforementioned problems. Another object is to propose a device of the aforementioned type which shows some improvement.

The device is defined in the appended claims, in which the dependent ones define advantageous variants.

The device works to adjust the linear position of one or more shutters in an injection molding system, wherein the shutter can open and/or close a molten-fluid supply channel to one or more mold cavities by translating along an axis. To adjust the shutter's end of stroke, the device comprises:a body comprising a cavity in which there can slide axially a movable element, to which the one or more shutters can be fixed;a fixed support plate,an adjustment element for adjustment of the axial position of the body, wherein the adjustment elementis rotatably mounted between the body and the plate,is connected to the body and to the plate so that it can be rotated clockwise and/or counter-clockwise so as to move linearly parallel to said axis in order to define the position of the body along said axis, andcomprises a threaded portion on which a corresponding thread of the body and/or of the support plate is engaged.

Thus, by turning the adjustment element more or less, one can translate the body along said axis, obtaining the adjustment of the end of stroke.

The adjustment element may be coupled to the body and to the support plate in different ways. E.g. the adjustment element may have only one threaded portion, which is engaged with a corresponding thread of the support plate or body. Or the adjustment element may have two threaded portions which are respectively engaged on a corresponding thread of the support plate and body.

In the first case (single thread), the adjustment element may have a (e.g. external) thread (such as thread62in the figures) while internally it has no thread; and the coupling between the body and the adjustment element is not of the threaded type, but for example by sliding interlocking or by abutting parts. In this variant there is no relative translation between the adjustment element and the body but only between the adjustment element and the support plate.

In another variant of the single thread, the adjustment element may have a (for example internal) thread (as for example the thread64of the figures) engaged on a thread of the body, while externally the adjustment element is devoid of any thread. When the adjustment element is rotated, the body translates with respect to the adjustment element, while the adjustment element rotates with respect to the support plate but remains in axial stationary position with respect to the support plate.

In the second case (double thread), the adjustment element is mounted screwably into the support plate, and can be screwed clockwise and/or counter-clockwise inside the support plate to move linearly and define an axial position of the body, and the body and the support plate comprise threaded portions on which the adjustment element is engaged simultaneously with corresponding threads of its own. Therefore, by screwing more or less the adjustment element into the plate one is able to translate the body along said axis, obtaining the adjustment of the end-of-stroke.

The device has e.g. a movable piston inside an outer casing fixed to the hot runner, or to a plate of the mold, or to another support element.

According to a preferred variant, the threaded portions of the body and of the support plate and the corresponding threads of the adjustment element are concentric to said axis. In this way the symmetry of the device simplifies the construction. A solution with threads non-concentric to the shutter axis is also possible.

According to a preferred variant, the body comprises a male portion, e.g. a central neck, which is externally threaded and protrudes along said axis from an end of the body, and on the male portion there is a thread engaged by a thread present in a corresponding female portion of the adjustment element. This solution facilitates the coupling between the body and the adjustment element, while ensuring at the same time symmetry of the structure and robustness. Or the adjustment element could comprise a male part that can be screwed into a complementary female part of the body (the male part in this case would be externally equipped with a thread).

According to a preferred variant the adjustment element comprises threads formed on one of its outer and inner side walls, in order to simplify the construction of the adjustment element. Said internal side wall can correspond to a pass-through or blind opening of the adjustment element.

To improve the efficiency and reliability of the system, preferably the device comprises blocking means or elements for blocking the adjustment element with respect to the plate and/or the body.

The blocking means or elements can be implemented in different ways.

In a variant, the blocking means or elements are mounted on the adjustment element. E.g. the adjustment element comprises deformable portions able to be pushed with pressure against the plate and/or the body to block the adjustment element with respect to the plate and/or the body. E.g. the adjustment element may comprise two concentric threaded rings that are axially spaced apart and able to be spread apart and pressed with pressure against a corresponding thread of the plate and/or body. The two concentric threaded rings are preferably equal and/or of equal diameter, for ease of construction.

In a different variant, the blocking means or elements are mounted on the fixing plate. E.g. the fixing plate comprises deformable portions able to be pushed with pressure against the adjustment element to block it. Or the fixing plate comprises blocking elements able to be pushed against the adjustment element to block it.

In the figures: identical numerical references indicate equal elements, and parts are described as in use.

A device10for adjusting the linear position of a shutter20in an injection molding system12(shown only partially) is illustrated altogether inFIG. 1. The shutter20in a known manner can open and/or close a molten fluid channel supplying a mold cavity (not shown) by moving forward and/or backward along a Z axis.

The device10comprises an outer body14which delimits (seeFIG. 2) an internal cavity16in which a piston18can slide axially and be directly or indirectly connected to the shutter20. The linear displacement of the piston18involves the linear displacement of the shutter20along the Z axis.

The outer body14is slidably mounted on columns22to be linearly translatable along Z with respect to the system12, and therefore define an adjustable end of stroke for the shutter20. The outer body14comprises an upper circular neck34which protrudes upwardly along Z and is externally equipped with a thread36.

On the top of the columns22there is mounted an upper support plate30, fixed with respect to the system12and lying on a plane orthogonal to the Z axis.

The plate30has in its center a circular pass-through opening on whose side walls there is a thread32. Such opening serves to house an adjustment ring nut60(see alsoFIG. 5), which is provided externally with a thread62and in turn comprises a pass-through or blind central circular cavity66on whose side walls there is a thread64(seeFIG. 5).

The ring nut60is sized and mounted so that the thread64is engaged on the thread36of the neck34and the thread62is engaged on the thread32of the plate30. In this way the ring nut60can be screwed clockwise and/or counter-clockwise inside the plate30to move linearly along the Z axis and simultaneously move the body14along the Z axis.

From the foregoing it is understood that the device10allows defining easily an axial position of the body14along Z, a condition that automatically establishes the upper stroke limit for the piston18. It is enough to screw more or less the ring nut60into the plate30so that the ring nut60, by reaction, moves the neck34up or down along the Z axis.

It is preferable to be able to lock the ring nut60in place after adjustment, to ensure precision and repeatability in the molding processes.

For this purpose, a preferred construction of the ring nut60(FIG. 5) provides for it to comprise two equal parallel threaded discs70,72axially separated by a diametral connection74, also equipped with a thread. A similar structure can e.g. be obtained by milling laterally a threaded cylinder. Disc70is the one on the opposite side with respect to the body14, and has pass-through, internally threaded holes76. By screwing a threaded dowel90(FIG. 3) into one or more holes76until the underlying disc72is touched by the dowel90, the two discs70,72can be slightly spread apart so as to press the threads62,32one against the other. The thus enhanced friction between the threads62,32achieves the locking of the ring nut60.

More generally, a preferred solution for the ring nut60provides that it has a deformable geometry or portion. The deformable portion is capable to cooperate with an external element, e.g. a screw, capable of deforming the/a thread of the ring nut to ensure blocking thereof.

Or, another preferred solution for the ring nut provides that in the ring nut there are made e.g. one or more holes inside which one or more threaded dowels can be inserted. The dowels are able to spread apart the upper and lower flaps of the ring nut thus achieving its locking.

Another variant for locking the ring nut is shown inFIG. 4. For the ring nut the splayable/deformable structure ofFIG. 5is no longer necessary, and it can be a simple full ring nut, indicated with60b. Through a hole in the plate30one or more dowels can be inserted to lock laterally the adjustment ring nut. Here a dowel blocks the position of the ring nut60bby exerting pressure on the external thread of the ring nut60b.

A further solution for locking the adjustment ring nut envisages the use of a further locking plate cooperating with one or more connection elements, for example plugs, able to lock the adjustment ring nut.

Or the plate30may have a splayable/deformable structure for locking a ring nut60b(FIG. 4). In particular, the plate30comprises an outermost lip92integral with a base plate94except for radials openings in which a dowel98can be inserted along a plane orthogonal to the Z axis. The dowel98can divaricate the lip92with respect to the base plate94, with the effect described above on the threads32,62, or interfere on/with the thread62to lock the ring nut60b.