(19)
(11)EP 3 797 966 A1

(12)EUROPEAN PATENT APPLICATION

(43)Date of publication:
31.03.2021 Bulletin 2021/13

(21)Application number: 20198818.5

(22)Date of filing:  28.09.2020
(51)Int. Cl.: 
B29C 45/38  (2006.01)
B29C 45/27  (2006.01)
(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
Designated Extension States:
BA ME
Designated Validation States:
KH MA MD TN

(30)Priority: 26.09.2019 PT 2019115798

(71)Applicant: Simoldes Plásticos, SA
Oliveira de Azeméis, 3721-902 Santiago de Riba-UL (PT)

(72)Inventor:
  • DE OLIVEIRA AZENHA, Manuel Joaquim
    3721-902 Oliveira de Azemeis (PT)

(74)Representative: Patentree 
Edificio Net Rua de Salazares, 842
4149-002 Porto
4149-002 Porto (PT)

  


(54)DEVICE FOR AUTOMATICALLY TRIMMING INJECTION GATES, OPERATING METHOD AND OBTAINED PRODUCT THEREOF


(57) A device for, operating method thereof and obtained product by automatically trimming an injection moulding gate of a moulded product being obtained by injection moulding in a mould, as a result of injecting melted injection material through an opening in said mould, comprising: a casing for attaching to the mould; a blade for trimming the gate, arranged to move perpendicularly to the direction of melted material injection of said opening; a feeding slider comprising a runner inlet forming a channel in said feeding slider; wherein the blade is movable from an injection position away from the opening to a cutting position, cutting the gate, and closing the opening; wherein the feeding slider is movable from an injection position, arranged against the mould opening such that the runner inlet establishes a fluid-tight channel into the mould, to a cutting position, arranged to hold the blade against the mould opening to maintain holding pressure by the blade.




Description

TECHNICAL FIELD



[0001] The present disclosure relates to the field of injection moulding, in particular to a device for trimming injection gates.

BACKGROUND



[0002] Injection moulding, specifically plastic injection moulding has been the preferred process for manufacturing plastic parts. Advantages include higher tolerance precision, lower labour costs and a lesser need to finish parts after moulding. Disadvantages of injection moulding are for example process limitations.

[0003] The injection moulding cycle usually involves injecting molten polymer through a channel, normally heated. The molten polymer flows through channels, called runners, and enters a mould cavity through a runner and gate inlet. The mould remains in the mould cavity at a set temperature to allow the polymer to solidify. Once the mould cavity is filled, a holding pressure is usually maintained to ensure adequate moulding and/or compensate for material shrinkage. This is referred to as the pack/hold phase of the cycle. Pressure must be maintained on the material until the gate solidifies to prevent material from flowing back out of the cavity. Once the mould is sufficiently cooled, the mould opens and the hardened moulded product is ejected.

[0004] Injection moulding processes are subject to material stress. When a polymer is melted, the molecular bonds are temporarily broken due to the heat and shear force of the extruder thus allowing the molecules to flow. As the polymer cools and the molecular bonds re-link the polymer into its rigid form, unequal distribution of stresses can cause warpage, sink marks, cracking, premature failure and other problems.

[0005] Each injection mould design has a gate that allows the molten polymer to be injected into the mould cavity. Gate type, design and location can affect part packing, gate removal or vestige, cosmetic appearance, dimensions and warping. There can be mentioned two current types of gates: manually trimmed gates and automatically trimmed gates.

[0006] Manually trimmed gates require an operator to separate the mould manually after each cycle. Manually trimmed gates have advantages for shear-sensitive materials which cannot be exposed to high shear rates. However, such gate designs are laborious and not cost effective.

[0007] Automatically trimmed gates incorporate tools for cutting or trimming the gates when the mould opens to eject the solidified mould. Automatically trimmed gates avoid the need for a secondary operation thus reducing cost. It also minimises gate scars.

[0008] Despite these advantages, there are disadvantages in the current automatically trimmed gates. Specifically, the prior art designs are complex, not easily reused on different moulds, all contributing to cost and practical complications, for example involving multiple movements, in the mould design, construction and operation.

[0009] Document CN101733904A discloses a mould inner gate arranged for automatically cutting off an injection mould. The automatic in-mould edge gate cutting injection mould wherein the gate cutting device comprises a plurality of cutters, a separation inhibiting device and a mould separating damper.

[0010] In document CN101733904A, the mould opening force of an injection machine is used for cutting off a gate runner in the process of mould opening. The cutters exhibit shearing movements opposite to the edge gate through the spring force at the bottom of the cutters.

[0011] Document CN203046155U discloses a cutoff-type injection mould. The cutoff-type injection mould comprises a top cover at upper end, a fixed die and a dynamic die at the lower end of the top cover, and a base structure at bottom, wherein the fixed die and the dynamic die are vertically arranged in correspondence; a groove is arranged in the lower end of the fixed die; a mould pressing groove is arranged in the groove; a mould pressing plate is arranged in the upper end of the dynamic die; the mould pressing groove and the mould pressing plate are oppositely arranged; a plurality of inclined ejector pins are connected at the lower end of the mould pressing plate, and the inclined ejector pins are connected onto a surface pin plate through a sliding wheel; and a plurality of cutters are arranged at two sides of the mould pressing groove.

[0012] Document DE4033297A1 discloses a mould for injection moulding of plastics, which has on one of the two halves of the mould a frame. This urges during the closure of the mould web of foil through a mask in the second half of the mould. The frame can slide from a protruding to a flush fitting position in the first half of the mould due to a spiral spring. Cutters to trim the web are fitted to the first half of the mould.

[0013] There is thus a need for a device for automatically trimming injection gates for which the design is not complex, easily reused on different moulds, reducing costs and practical complications (e.g. avoiding multiple movements) in the mould design, construction and operation.

[0014] These facts are disclosed in order to illustrate the technical problem addressed by the present disclosure.

GENERAL DESCRIPTION



[0015] The present disclosure relates to a device for trimming, i.e. cutting, injection mould gates, operating automatically, i.e. without manual operation.

[0016] Gate type, design and location can affect part packing, gate removal or vestige, cosmetic appearance, dimensions and warping. There are two types of gates which can be mentioned in the present context: manually trimmed gates and automatically trimmed gates.

[0017] Manually trimmed gates require a human operator to separate the moulded gate material manually from the moulded product after each cycle. Manually trimmed gates have advantages for shear-sensitive materials which cannot be exposed to high shear rates. However, such gate designs are laborious and not cost effective.

[0018] Automatically trimmed gates incorporate tools for cutting or trimming the gates when the mould opens to eject the solidified moulded product. Automatically trimmed gates avoid the need for a secondary operation thus reducing cost. It also minimises gate scars. Despite these advantages, there are disadvantages in the current automatically trimmed gates. Specifically, the designs are complex, not easily reused on different moulds and/or involve multiple movements, all contributing to cost and practical complications in the mould design, construction and operation.

[0019] The present disclosure describes a device for automatically trimming injection gates. The disclosure also describes a method for operating the device for automatically trimming injection gates. The obtained moulded product shows a gate trimming surface that is less strained or less scarred that prior art moulded products.

[0020] It is disclosed a device for automatically trimming an injection moulding gate of a moulded product being obtained by injection moulding in a mould, as a result of injecting melted injection material through an opening in said mould, comprising:

a casing for attaching to the mould;

a blade for trimming the gate, arranged to move substantially perpendicularly to the direction of melted material injection of said opening;

a feeding slider comprising a runner inlet forming a channel in said feeding slider;

wherein the blade is movable from an injection position away from the opening to a cutting position, cutting the gate, and closing the opening;

wherein the feeding slider is movable from an injection position, arranged against the mould opening such that the runner inlet establishes a fluid-tight channel into the mould, to a cutting position, arranged to hold the blade against the mould opening to maintain holding pressure by the blade.



[0021] In an embodiment, the feeding slider is arranged to move substantially in parallel to the direction of melted material injection of said opening.

[0022] In an embodiment, the blade and the feeding slider cooperate by way of respective cooperating sloped surfaces.

[0023] In an embodiment, the blade is arranged to move perpendicularly to the feeding slider.

[0024] An embodiment comprises a locking bar movable from an injection position, held as a wedge between the casing and the feeding slider to lock the feeding slider in position arranged against the mould opening such that the runner inlet establishes a fluid-tight channel into the mould, to a cutting position, unlocking the feeding slider to move away from the opening and holding feeding slider to hold the blade against the mould opening to maintain holding pressure by the blade.

[0025] In an embodiment, the feeding slider and the locking bar cooperate by way of respective cooperating sloped surfaces.

[0026] In an embodiment, the movable locking bar is arranged to arranged to move in parallel and in reciprocal motion to the blade.

[0027] An embodiment comprises an actuator for moving the blade from the injecting position into the cutting position.

[0028] An embodiment comprises a hydraulic cylinder and a piston for moving the blade from the injecting position into the cutting position.

[0029] In an embodiment, the hydraulic cylinder and a piston are further arranged for moving the blade from the injecting position into the cutting position.

[0030] An embodiment comprises a gear meshing with the blade and the feeding slider to synchronise movement of the blade and the feeding slider.

[0031] In an embodiment, the gear meshes with the blade, the feeding slider and the locking bar, to synchronise movement of the blade, the feeding slider and the locking bar.

[0032] An embodiment comprises a gear meshing with the blade and locking bar, but not the feeding slider, to synchronise movement of the blade and the locking bar.

[0033] An embodiment comprises a further hydraulic cylinder and a piston arranged to move the locking bar.

[0034] In an embodiment, its parts are arranged to be movable bi-directionally between the injecting position and the cutting position.

[0035] It is also disclosed a method of operating a device for automatically trimming an injection moulding gate according to any of the disclosed embodiments, comprising the steps of:

previously, arranging the device against a mould opening and arranging a feeding channel into the runner inlet of the feeding slider, wherein the blade is moved away from the mould opening, and simultaneously, or previously, the feeding slider is moved against the mould opening, such that the runner inlet establishes a fluid-tight channel from the feeding channel through the mould opening and into the mould;

injecting melted polymer into the mould cavity via the runner inlet of the feeding slider;

optionally, allowing injecting pressure to ease to a lower pressure than the injection pressure;

moving the blade into cutting position, and simultaneously, or previously, moving the feeding slider from the mould opening, such that the feeding slider holds the blade against the mould opening, and thus maintaining holding pressure until the moulded product solidifies;

optionally, returning to injection pressure, if the pressure was previously eased from the injection pressure;

allowing the mould to cool and the moulded product to solidify;

opening the mould and extracting the moulded product.



[0036] In an embodiment, the blade is moved into the cutting position when the product has partially solidified such that the blade movement is not impaired, but the melted material pressure has reduced due to the partial solidifying, such that the risk of leakage is reduced.

[0037] It is also disclosed a moulded product obtained by the method according to the disclosed embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS



[0038] The following figures provide preferred embodiments for illustrating the disclosure and should not be seen as limiting the scope of invention.

Figure 1: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates in (a) injecting position and (b) cutting position.

Figure 2: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates in (a) injecting position and (b) cutting position.

Figure 3: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates in (a) injecting position and (b) cutting position.

Figure 4: Schematic representation of a cross-section of two embodiments, in injecting position, of the device for automatically trimming injection gates.

Figure 5: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates in (a) injecting position and (b) cutting position.

Figure 6: Schematic representation of a cross-section of two embodiments, in injecting position, of the device for automatically trimming injection gates.

Figure 7: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould - injection position.

Figure 8: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould - the injection is closed, and the blade is the cutting position.

Figure 9: Schematic representation of a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould - the ejection of the part is done, and part and runner are separated.


DETAILED DESCRIPTION



[0039] This disclosure relates to a device for automatically trimming injection gates. This disclosure further relates to movement mechanisms for the device for automatically trimming injection gates.

[0040] One of the main limitations of the injection moulding process is due to material stress. When a polymer is melted, the molecular bonds are temporarily broken due to the heat and shear force of the extruder thus allowing the molecules to flow. As the polymer cools and the molecular bonds re-link the polymer into its rigid form, unequal distribution of stresses can cause warpage, sink marks, cracking, premature failure and other problems.

[0041] Each injection mould design has a gate that allows the molten polymer to be injected into the mould cavity. Gate type, design and location can affect part packing, gate removal or vestige, cosmetic appearance, dimensions and warping. There are currently two types of gates: manually trimmed gates and automatically trimmed gates.

[0042] Manually trimmed gates require an operator to separate the mould manually after each cycle. Manually trimmed gates are advantages for shear-sensitive materials which cannot be exposed to high shear rates. However, such gate designs are laborious and not cost effective.

[0043] Automatically trimmed gates incorporate tools for cutting or trimming the gates when the mould opens to eject the solidified moulded product. Automatically trimmed gates avoid the need for a secondary operation thus reducing cost. It also minimises gate scars. Despite these advantages, there are disadvantages in the current automatically trimmed gates. Specifically, the prior art designs are complex, not easily reused on different moulds, all contributing to cost and practical complications, for example involving multiple movements, in the mould design, construction and operation. Also, scars remain visible even when minimised with prior art methods.

[0044] The present disclosure describes an improved automatically trimmed gate system. This disclosed device is less complex, easily reused on different moulds, reducing cost and practical complications, involving a single movement.

[0045] Figure 1(a) illustrates the cross-section of an embodiment of the injection gate trimming device comprising a casing 1 which encloses a blade 2 for trimming the gate, a movable feeding slider 3 and a runner inlet 4 forming a channel in said feeding slider. The movable feeding slider 3 is arranged flush against the interior of the casing 1, proximal to the mould such that the runner inlet 4 establishes a fluid-tight channel into the mould. The blade 2 is elevated, arranged parallel to the interior of the casing and perpendicular to the movable feeding slider 3. Melted polymer can be injected into the moulding cavity via the runner inlet 4. When the cutting device is activated to cut the mould gate, the blade 2 is lowered, simultaneously cutting the gate and closing the mould opening, and the movable feeding slider 3 is shifted to its distant position as illustrated in Figure 1(b). The movable feeding slider 3, by way of cooperating sloped surfaces in the blade 2 and the slider 3, holds the blade 2 against the mould opening, and thus maintaining holding pressure until the moulded product solidifies. In particular, the feeding slider 3 is held against the blade 2 by the casing 1, as the casing 1 prevents the slider from moving further away from the mould opening, and thus maintaining holding pressure until the moulded product solidifies.

[0046] Figure 2(a) illustrates the cross-section of an embodiment of the injection gate trimming device comprising a casing 1 which encloses a blade 2 for trimming the gate, a movable feeding slider 3, a runner inlet 4 forming a channel in said slider, and a movable locking bar 5. The movable feeding slider 3 is arranged flush against the interior of the casing 1, proximal to the mould such that the runner inlet 4 establishes a fluid-tight channel into the mould. The blade 2 is elevated, arranged parallel to the interior of the casing and perpendicular to the movable feeding slider 3 movement. Melted polymer can be injected into the moulding cavity via the runner inlet 4. When the cutting device is activated to cut the mould gate, the blade 2 is lowered, simultaneously cutting the gate and closing the mould opening, and the movable feeding slider 3 is shifted to its distant position as illustrated in Figure 1(b).

[0047] The movable feeding slider 3, by way of as cooperating sloped surfaces in the blade 2 and the slider 3, holds the blade 2 against the mould opening. In particular, the feeding slider 3 is held against the blade 2 by the casing 1, as the casing 1 prevents the slider from moving further. The movable locking bar 5, functioning as a locking mechanism, can be lowered, parallel to the interior of the casing and perpendicular to the movable feeding slider 3. The movable locking bar 5 cooperates with the movable feeding slider 3 by way of respective cooperating sloped surfaces. In its lowered position, the movable locking bar 5 locks the movable feeding slider in its injecting position (a). When the cutting device is activated to cut the mould, the blade 2 is lowered, the movable feeding slider 3 is moved away from the mould opening and, the movable locking bar 5 is elevated as illustrated in Figure 2(b).

[0048] In this way, two locking mechanisms are obtained. A first locking mechanism, in the injecting position (a), is obtained by the locking bar 5 being held, as wedge, between the casing 1 and the feeding slider 3 to maintain holding pressure of the feeding slider 3 against the mould opening during injection. This is advantageous for higher injection pressures. A second locking mechanism, in the cutting position (b), is obtained by the feeding slider 3 when held against the blade 2 by the casing 1, as the casing 1 prevents the slider from moving further away from the mould opening and thus maintain holding pressure until the moulded product solidifies.

[0049] Figure 3 illustrates the cross-section of an embodiment of the injection gate trimming device in (a) injecting position and (b) cutting position. In this embodiment, a hydraulic cylinder 7 and a piston 8 are used to move the blade 2. The feeding slider 3 may be moved from the injecting position to the cutting position by way of the cooperating sloped surfaces of the blade 2 and the feeding slider 3. The locking bar 5 may also be moved from the injecting position to the cutting position by way of the cooperating sloped surfaces of the feeding slider 3 and the locking bar 5. This requires that the sloped surface angles are adjusted so that the mechanism moves adequately.

[0050] Preferably, a gear 6 may be used, i.e. a toothed wheel, meshing with corresponding holes in two or more of the blade 2, feeding slider 3 and locking bar 5 to facilitate simultaneous movement of the these parts. In particular, the gear 6 may comprise multiple teeth for meshing with the blade 2 or locking bar 5. In particular, the gear 6 may comprise a single curved tooth for meshing with the feeding slider 3. The gear 6 rotates anti-clockwise when moving from the (a) injecting position into the (b) cutting position, and vice-versa.

[0051] Figure 4(a) illustrates an alternative gear 9. The alternative gear 9 meshes with the blade 2 and locking bar 5, but not the feeding slider 3. This is advantageous in being a simpler mechanism, but requires the sloped surface angles to be adjusted so that the mechanism moves adequately.

[0052] Figure 4(b) illustrates the cross-section of an embodiment of the injection gate trimming device in (a) injecting position and (b) cutting position, with an alternative actuating mechanism. A second hydraulic cylinder 10 and a second piston 11 are arranged to move the locking bar 5. The feeding slider 3 may be moved from the injecting position to the cutting position by way of the cooperating sloped surfaces of the blade 2 and the feeding slider 3. The feeding slider 3 may also be moved from the cutting position to the injecting position by way of the cooperating sloped surfaces of the feeding slider 3 and the locking bar 5.

[0053] The disclosed embodiments can move bi-directionally between the (a) injecting position and the (b) cutting position.

[0054] In one embodiment, a method for operating the injection gate trimming device, comprises the following steps:
  1. 1. previously, arranging the device against a mould opening and arranging a feeding channel into the runner inlet 4 of the feeding slider 3;
  2. 2. moving the blade 2 away from the mould opening;
  3. 3. moving the feeding slider 3 against the mould opening, such that the runner inlet 4 establishes a fluid-tight channel from the feeding channel through the mould opening and into the mould;
  4. 4. injecting melted polymer into the mould cavity via the runner inlet 4 of the feeding slider 3;
  5. 5. optionally, allowing injecting pressure to ease to a lower pressure than the injection pressure;
  6. 6. moving the blade 2 into cutting position;
  7. 7. moving the feeding slider 3 from the mould opening, such that it holds the blade 2 against the mould opening, and thus maintaining holding pressure until the moulded product solidifies;
  8. 8. optionally, returning to injection pressure, if the pressure was previously eased from the injection pressure;
  9. 9. allowing the mould to cool and the moulded product to solidify;
  10. 10. opening the mould and extracting the moulded product.


[0055] Note that steps 2 and 3 are preferably carried out simultaneously by way of the disclosed mechanism. Note that steps 6 and 7 are preferably carried out simultaneously by way of the disclosed mechanism. Note that step 1 may be carried out before, during, or after steps 2 and 3.

[0056] Subsequently, the mould and the injection gate trimming device may be prepared for a new injection process. The movement is then reversed, which comprises moving the blade 2 away from the mould opening and moving the feeding slider 3 against the mould opening, such that the runner inlet 4 establishes a fluid-tight channel from the feeding channel through the mould opening and into the mould. This subsequent movement for device preparation for a new injection may be carried out between steps 9 and 10. Note that in step 9, the moulded product does need to be completely solidified before the reverse movement is carried out, what is necessary is that the gate has sufficiently solidified such that the blade 2 may be removed from the mould opening.

[0057] Figure 7 illustrates of a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould having a first mould half 21 and a second mould half 22. There is also a hot injection inlet 23. The device is in the injection position: the blade 2 is away from the opening, letting the injection material enter through the injection opening, and the feeding slider 3 is arranged against the mould opening such that the runner inlet 4 establishes a fluid-tight channel into the mould.

[0058] Figure 8 illustrates a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould - the injection is closed, and the device is in the injection position: the blade 3 is cutting the gate and closing the opening, and the feeding slider 3 is holding the blade 2 against the mould opening to maintain holding pressure by the blade 2.

[0059] Figure 9 illustrates a cross-section of an embodiment of the device for automatically trimming injection gates placed in an injection mould - the ejection of the part (referred as p) is done, and part and runner are separated. The injection material has been separated between part p and runner injection material 34 by a cut 32 performed by the blade 2.

[0060] Figures 7-9 also illustrate how the disclosed device is removable from the mould so that the device can be re-used in another mould.

[0061] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof. The above described embodiments are combinable. The following claims further set out particular embodiments of the disclosure.


Claims

1. A device for automatically trimming an injection moulding gate of a moulded product being obtained by injection moulding in a mould, as a result of injecting melted injection material through an opening in said mould, comprising:

a casing (1) for attaching to the mould;

a blade (2) for trimming the gate, arranged to move substantially perpendicularly to the direction of melted material injection of said opening;

a feeding slider (3) comprising a runner inlet (4) forming a channel in said feeding slider (3);

wherein the blade (2) is movable from an injection position (a) away from the opening to a cutting position (b), cutting the gate, and closing the opening;

wherein the feeding slider (3) is movable from an injection position, arranged against the mould opening such that the runner inlet (4) establishes a fluid-tight channel into the mould, to a cutting position, arranged to hold the blade (2) against the mould opening to maintain holding pressure by the blade (2).


 
2. The device for automatically trimming an injection moulding gate according to the previous claim, comprising a locking bar (5) movable from an injection position, held as a wedge between the casing (1) and the feeding slider (3) to lock the feeding slider (3) in position arranged against the mould opening such that the runner inlet (4) establishes a fluid-tight channel into the mould, to a cutting position, unlocking the feeding slider (3) to move away from the opening and holding feeding slider (3) to hold the blade (2) against the mould opening to maintain holding pressure by the blade (2).
 
3. The device for automatically trimming an injection moulding gate according to any of the previous claims, comprising a gear (6) meshing with the blade (2) and the feeding slider (3) to synchronise movement of the blade (2) and the feeding slider (3).
 
4. The device for automatically trimming an injection moulding gate according to any of the previous claims, wherein the feeding slider (3) is arranged to move substantially in parallel to the direction of melted material injection of said opening.
 
5. The device for automatically trimming an injection moulding gate according to any of the previous claims, wherein the blade (2) and the feeding slider (3) cooperate by way of respective cooperating sloped surfaces.
 
6. The device for automatically trimming an injection moulding gate according to the previous claim, wherein the blade (2) is arranged to move perpendicularly to the feeding slider (3).
 
7. The device for automatically trimming an injection moulding gate according to claim 2 or any of the claims 3-6 when dependent on claim 2, wherein the feeding slider (3) and the locking bar (5) cooperate by way of respective cooperating sloped surfaces.
 
8. The device for automatically trimming an injection moulding gate according to the previous claim, wherein the movable locking bar (5) is arranged to arranged to move in parallel and in reciprocal motion to the blade (2).
 
9. The device for automatically trimming an injection moulding gate according to any of the previous claims, wherein the runner inlet (4) is a recess in a surface of the feeding slider (3) such that it forms a fluid-tight channel in said feeding slider (3) when a feeding channel is connected to said recess.
 
10. The device for automatically trimming an injection moulding gate according to any of the previous claims, wherein the feeding slider (3) is movable from an injection position, arranged against the mould opening such that the runner inlet (4) establishes a fluid-tight channel into the mould, to a cutting position, arranged to hold the blade (2) against the mould opening to maintain holding pressure by the blade (2).
 
11. The device for automatically trimming an injection moulding gate according to any of the previous claims, comprising an actuator for moving the blade (2) from the injecting position into the cutting position.
 
12. The device for automatically trimming an injection moulding gate according to any of the previous claims, comprising a gear (9) meshing with the blade (2) and locking bar (5), but not the feeding slider (3), to synchronise movement of the blade (2) and the locking bar (5).
 
13. The device for automatically trimming an injection moulding gate according to any of the claims 5 - 7, comprising a further hydraulic cylinder (10) and a piston (11) arranged to move the locking bar (5).
 
14. Method of operating a device for automatically trimming an injection moulding gate according to any of the previous claims, comprising the steps of:

previously, arranging the device against a mould opening and arranging a feeding channel into the runner inlet (4) of the feeding slider (3), wherein the blade (2) is moved away from the mould opening, and simultaneously, or previously, the feeding slider (3) is moved against the mould opening, such that the runner inlet (4) establishes a fluid-tight channel from the feeding channel through the mould opening and into the mould;

injecting melted polymer into the mould cavity via the runner inlet 4 of the feeding slider (3);

optionally, allowing injecting pressure to ease to a lower pressure than the injection pressure;

moving the blade (2) into cutting position, and simultaneously, or previously,

moving the feeding slider (3) from the mould opening, such that the feeding slider (3) holds the blade (2) against the mould opening, and thus maintaining holding pressure until the moulded product solidifies;

optionally, returning to injection pressure, if the pressure was previously eased from the injection pressure;

allowing the mould to cool and the moulded product to solidify;

opening the mould and extracting the moulded product.


 
15. Moulded product obtained by the method according to the previous claim.
 




Drawing


























REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description