TITLE OF THE INVENTION

IMPROVED SIDE GATE TYPE MOLD ARRANGEMENT WITH POINTED HEAT-GENERATING MODULE TECHNICAL FIELD The present invention relates to a new pointed intermittently heat-generating module having a heating tip for use in runnerless injection-molding of plastic material, which module is to be incorporated with a side gate of a mold cavity, and an improved mold arrangement defining the cavity with the side gate, wherein the new module is allowed to extend in a direction of a mold axis with the tip being received in the side gate. BACKGROUND ART

U.S. Patent NO..3,800,027 discloses an original pointed intermittently heat-generating module, and U.S. patent no. 4,643,664 discloses an improvement from the original one.

The disclosed modules are all directed to ones to be incorporated with a gate open to a mold cavity in a direction of a mold axis, a so called "axial gate", while the "side gate" is open to a corresponding cavity in a direction perpendicular to the mold axis.

The conventional module is very effective in heating a cold part of the plastic material at the axial gate temporarily and instantaneously to open the gate for the injection-molding. The cold material part is a part integrated with a molded article in the cavity but separated therefrom after the mold is opened for removal of the article, and is integrated with a hot remaining part of the material staying in a mold arrangement.

This is true because the module has a heating axial tip to be received in the axial gate with an annular space gap formed therebetween. The module has a longitudinal body forming a passage for the material therein with an outlet in the vicinity of the axial tip

for communicating a runner passage of a hot runner mold, which communicates with a nozzle of an injection machine, with the axial gate so that a hot material is allowed to flow from the nozzle to the mold cavity through the runner passage and the annular space gap formed in the axial gate. The cold material part fills the annular space gap, which is designed to have a small thickness relative to the axial gate or the axial tip. Therefore, the cold material part can be easily and quickly fused or melted by the instantaneous heating of the aixal tip.

A conventional mold arrangement involving an axial gate comprises a stationary cavity half block, which defines a cavity half with the axial gate and also forms by itself an axial through-hole for a module to be received therein and to which hole the axial gate is open.

If the axial tip were not allowed to be received in the axial gate in such a manner as above and thus were obliged to stay in front of the axial gate in use, the tip would be required to impart a relatively large amount of heat energy to the cold material part occupying the entire space of the axial gate. This assumed case would be ineffective in opening the gate instantaneously for injection-molding, or otherwise would require a larger heat energy or a longer time for an effective switching operation of opening the gate.

However, fortunately, the conventional mold arrangement involving such axial gate, as a nature of its construction, allows the conventional module having such axial tip to be received in the axial gate when incorporated with the module such that the module extends axially in the axial through-hole or recess of the mold arrangement.

In turn, a conventional mold arrangement involving a side gate comprises a stationary cavity half block, which defines a cavity half with the side gate and forms by itself an axial recess or through-hole for a module to be

received therein to which hole the side gate is open, and thus does allow a module having such axial tip to be disposed axially but without the axial tip being received in the side gate. Further, an assumed module having a non-axial tip to be received in such side gate would not be allowed to have the module per se disposed axially in the axial recess or through-hole of the conventional mold arrangement involving the side gate. That is the non-axial tip per se would prevent the assumed module from being disposed axially into the conventional mold arrangement.

In this regard, there has been no module having a non-axial tip provided in practice, and no module allowed to have its tip received in a side gate of a conventional mold arrangement.

DISCLOSURE OF THE INVENTION

An object of the present invention is to solve the above-mentioned problem involving the side gate incorporated with the module tip. That is, the object is to provide an improved mold arrangement involving such side gate allowing a new module having a non-axial tip to be disposed axially therein with the non-axial tip being received in the side gate in use.

Another object of the present invention is to provide a new module having a plurality of non-axial tips for use in an improved mold arrangement having a plurality of cavities with side gates.

According to the present invention, there is provided a mold arrangement for use in runnerless injection molding of plastic material, comprising: a cavity mold having an axis and being divided into a stationary cavity mold half and an axially movable cavity mold half; a hot runner mold mounted on the stationary cavity mold half in a thermally insulated manner; and at least a pointed intermittent heat-generating module mounted in and extending axially from the hot runner mold. The stationary mold half defines at least one

cavity half having at least one non-axial or side gate open thereto in a direction perpendicular to the mold axis. The module has a longitudinal bored body with at least one heating tip. The module body formes a material passage therein having an outlet in the vicinity of the tip for communicating a runner passage of the hot runner mold with the side gate. The module is axially incorporated in the stationary cavity mold half such that the module tip is located at a corresponding cavity side gate for heating a cold part of the material at the side gate instantaneously and temporarily to open the side gate for injection-molding.

In the above arrangement, the module tip projects outside of the module body over an outer circumferential surface thereof in an inclined or non-aixal direction relative to a module axis. The side gate is defined to partially receive the non-axial tip therein in the first mentioned perpendicular direction at a fixed relative axial position. The stationary cavity mold half comprises: a stationary frame block enclosing an axial space defined as an axial through-hole; and at least one combination of a cavity half block, and a wedge spacer block for at least one module, axially tapering toward the hot runner mold. The axial space is provided: to axially receive the module, the cavity half block and the wedge spacer block individually therein; to allow the cavity half block to move in the first perpendicular direction by a fixed distance without the wedge spacer block being received in the axial space; and to render the cavity half block to be fixed in the first perpendicular direction with the non-axial tip being received in the non-axial or side gate at the axial position, due to the wedge spacer block being additionally disposed toward the hot runner mold in the axial space.

The axial space is provided: to allow the module to be axially received therein at a first fixed relative

position in the first perpendicular direction; to allow the cavity half block to be received therein and move therein in the first perpendicular direction between a second fixed relative position near the first perpendicular position and a third fixed relative position farther away from the first perpendicular position; and to allow the wedge spacer block to be axially received in a first part of the axial space defined by the frame block and the cavity half block when the latter is located at both the axial position and the second perpendicular position, while the cavity half block and the wedge spacer block are fixed in a second direction perpendicular to both the mold or module axis and the first perpendicular direction. The axial space is free to axially receive the module with the non-axial tip facing the side gate when the cavity half block is located at the third perpendicular position, but preventing the module from being disposed axially therein at the first perpendicular position until the axial position when the cavity half block is located at both the aixal position and the second perpendicular position. The wedge spacer block is disposed axially in the first space part to urge the cavity half block toward the second perpendicular position in the first perpendicular direction against the frame block.

The axial space comprises at least one combination of the first space part for the wedge spacer block, a second space part for the cavity half block integrated therewith and a third space part for the module. The second space part is constricted in a cross-sectional view to form a pair of opposing shoulders defining an axially extending slit, so that the cavity half block abuts against the paired shoulders at the second perpendicular position. The third space part is integrated with the second space part at the axially slit. The axial slit having a width large enough to allow the non-axial tip to move axially at the first

perpendicular position. The perpendicular distance by which the cavity half block is movable in the first and second space part combination is larger than a perpendicular length by which the non-axial tip extends from the .axial slit into the second space part at the first perpendicular position.

The axial space may form only a combination of the first, second and third space parts, and the third space part for the module is provided to axially receive the module with an annular and axial space for thermal insulation among the module body, the cavity half block and the frame block at the first perpendicular position, and first and second thermal-insulating spacer means are provided so as to be located opposite each other in the annular and axial space. The first spacer means forms a sealing ring encircling the non-axial tip and the passage outlet and defining a chamber between the cavity half block and the module body through which the material passage of the module communicates with the side gate. Alternatively, the axial space may have a fourth space part integrated with the third space part, and a separate part of the cavity half block without any cavity half formed therein is provided to have it received axially in the fourth space part. The separate cavity block part acts as an additional part of the frame block with a second spacer means similar to the above mentioned one abutting thereagainst.

According to the present invention, there is further provided a mold arrangement having the above mentioned construction, but being modified as follows:

The axial space has a cross section substantially symmetrical to a first line parallel to the second perpendicular direction or substantially rotation-symmetrical about the module axis such that said stationary cavity mold half comprises a frame block, a pair of combinations, each consisting of a substantially symmetric cavity half block having a substantially

symmetric side gate and a substantially symmetric wedge space block. Each of the symmetrical wedge spacer blocks and each of the cavity half blocks are axially received in substantially symmetric first and second space parts of the axial space, respectively. The third space part has a cross-sectional substantially symmetrical to the first line. At least one module having at least one pair of substantially symmetric non-axial tips extending opposite each other, and at least one pair of substantially symmetric passage outlets are provided to have the module received axially in the third space part between the symmetric cavity half blocks arranged in the first perpendicular direction with the symmetric tips projecting into the symmetric second space parts through substantially symmetric axial slits, respectively.

Preferably, the axial space of the frame block is a basically rectangular cross section with each of the blocks, to be received in the axial space, having a basically rectangular cross section. in practice, the stationary mold half further comprises a back plate block to be fixed to the frame block at the side of the hot runner mold to cover the axial space of the frame block except for the third space part thereof. The back plate block has an axial through-hole through which the module extends axially from the hot runner mold into the third space part of the frame block. All the blocks received in the axial space abut against the back plate block with at least the wedge spacer block being detachably fixed thereto. With a preferably module, every tip extends in a direction perpendicular to the module axis and conically tapers toward a free end thereof. The module is provided with an axial covering protector in a tube form which receives the module axially from a free end thereof and is used temporarily while the module is being disposed in the mold arrangement.

Preferably, the tube protector has opened and closed

ends, and at least one U-shape portion of the wall thereof at the opened end cut away to form an axial recess in the wall for a corresponding tip. The recess completely receives the tip but with the free end thereof being positioned below an outer imaginary surface of the cut-off U shaped wall portion in the perpendicular direction.

It should be appreciated that the above mentioned improved mold arrangement having the side gate in combination with the pointed intermittently heat-generating module having the axial tip disposed in the side gate is very advantageous in not only ensuring an effective gate opening operation, but also providing a stationary cavity half block allowed to have an enlarged width of a mold wall defined between a cavity half and an axial side surface at the side of the side gate, in other words have a perpendicular elongated side gate extending from the side surface to the cavity through the wall, relative to a conventional mold arrangement having a side gate in combination with a module having a substantially axially extending tip. This ensures the stationary cavity half block to be strengthened or reinforced due to the enlarged wall thickness, compared with the conventional one. BRIEF DESCRIPTION OF DRAWINGS

Figures 1 to 8 show a pointed intermittently heat-generating module according to the present invention, wherein: Figs. 1 and 2 are front and side views of the module, respectively; Fig. 3 is a side view of a module body showing a lead arrangement of a tip heater; and Figs. 4 to 8 are cross-sectional views taken along lines IV-IV, V-V, VI-VI, VII-VII and VIII-VIII in Fig. 1 or Fig. 2, respectively.

Fig. 9 is a cross-sectional view showing a main part of a first embodied mold arrangement according to the present invention in combination with a module similar to that as shown in Figs. 1 to 8, but modified with one of

the opposing tips omitted,

Fig. 10 is a cross-sectional view showing a main part of a second embodied mold arrangement according to the present invention in combination with the module as shown in Figs. 1 to 8,

Figs. 11 to 17 in combination show a process of assembling the second embodied mold arrangement with the module as shown in Figs. 1 to 8,

Fig. 18 is an enlarged cross-sectional view of a cavity half block as shown in Figs. 14, 15, 16, and 17, Fig. 19 is a cross-sectional view of a third embodied mold arrangement with a module according to the present invention, which view corresponds to Fig. 10,

Fig. 20 is a cross-sectional view taken along lines XX-XX in Fig. 19,

Fig. 21 is a plan view at line XXI-XXI in Fig. 19, Fig. 22 is a plan view of the third embodiment as shown in Fig. 19,

Figs. 23 and 24 are bottom views of stationary mold halves of two embodied mold arrangements, each with a plurality of dual opposite tip type modules according to the present invention, respectively.

Figs. 25 and 26 are bottom views of hot runner molds in two embodied mold arrangements, each with a plurality of dual opposite tip type modules according to the present invention, respectively, and

Figs. 27 to 33 show another embodied pointed intermittently heat-generating module according to the present invention, wherein: Figs. 27 and 28 are front and side views of the module, respectively; Fig. 29 is a rear view of the module; Figs. 30 to 33 are cross-sectional views taken along lines XXX-XXX XXXI-XXXI and XXXII-XXXII in Figs. 27, 28 or 33.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to Figs. 1 to 8, a pointed intermittently heat-generating module 1 according to the present invention has a longitudinal bored body 2, which forms a

passage 12 therein for hot plastic material with an outlet 13 open to a circumferential surface 3 of the body 2. The module is of a dual opposite tip type and thus has symmetrical opposite heating tips 4, which extend radially in opposite directions perpendicular to a module axis. Each tip 4 has a tip heater 16 therein. The body 2 has a cartridge heater 14 for heating the body therein to have the plastic material kept hot. 15 denotes leads of the tip heater 16 disposed in the bored body 2. 5 denotes a pair of thermal electrodes for the tip heater 16. 7 denotes a tube protector for leads of the body heater 14. 17 denotes a connection of the tip heater 16 to the leads 15, and 18 denotes an earthed lead part of the tip heater 16 at the ground. According to other embodiments of a module according to the present invention, the module may be of a single tip type as shown in Fig. 9, or a plural tip type as shown in Fig. 22. As an example of such plural tip type, Fig. 22 shows two pairs of dual opposite tips 4 provided in the module.

In any embodiment of the module, each tip 4 projects from the circumferential body surface 3 in a direction perpendicular to the module axis, and is of a stepped conical form. Referring to Fig. 10, a mold arrangement according to the present invention comprises a stationary mold half, a movable mold half (not shown in the drawings) and a hot runner mold or manifold 24. The stationary mold half comprises axially bored block elements 19, 20, 21, 22, 36 and 37. The block elements 20, 21 and 22 form in combination an axially bored back plate block. The block element 19 is a frame block enclosing an axial space X therein defined as a through-hole. The block elements 36 are symmetrical cavity half blocks, each defining a cavity half 36A with a side or non-axial gate 36B. 35 denotes mold articles attached to the cavity halves 36A. The block elements 37 are symmetrical wedge

spacer blocks, which are to be connected to the back plate block element 20 by bolts 42 as shown in Figs. 10, 16 and 17. The cavity half blocks 36 are also connected to the block 20 by means of bolts 43 as shown in Figs. 16 and 17. .

The symmetrical wedge spacer blocks 37, the symmetrical cavity half blocks 36 and the dual opposite non-axial tip type module 1 as shown in Figs. 1 to 8 can be received in first symmetrical space parts, second symmetrical space parts, and third space part of the axial space X in the frame block 19, respectively. The axial space X has a rectangular cross section, and the wedge spacer blocks 37 and the cavity half blocks 36 also have rectangular cross sections, respectively. Each of the cavity half blocks 36 is only allowed to move in a direction perpendicular to a mold axis in a combination of corresponding first and second space parts, if each wedge spacer block 37 is out of the axial space X, particularly out of a corresponding first space part. A possible perpendicular movement of the cavity half block 36 in each space part combination (36, 37) must be allowed to be a distance at the shortest equal to or a little bit smaller than a wall thickness t of the cavity half block 37 at side of the side gate 36B. Each second space part is constricted to have the frame block 19 form opposite shoulders 36a as shown in Figs. 20 and 21 and communicates with the third space part having a width smaller than that of the second space part. When the combination of the wedge spacer block 37 and the cavity half block 36 is received in the axial space, the cavity half block 36 abuts against the shoulders 36a, that is the wedge spacer block 37 urges the cavity half block 36 against the frame block 19 at the shoulders 36a. The cavity half blocks have circumferential grooves surrounding the side gates 36B and integrated therewith for having ring thermal pad insulators 33 rest therein, respectively. The ring pad insulators 33 are preferably

of titanium alloy. The module body surface 3 has opposite flat surface portions from which the tips 4 project and at the which the outlets 13 are located. The ring pad insulators 33 are located on the flat surface portions. The module 1 abuts against the opposite cavity half blocks 36 via the ring insulators 33 in the third space part, when the cavity half blocks 36 abut against the shoulders 36a in the second space part. In this case, each ring pad insulator 33 encircles a corresponding tip 4 and outlet 13, to define a chamber between the cavity half block 36 and the module 1. The side gate 36B and said non-axial tip 4 define an annular gate space gap therebetween extending in a direction perpendicular to the module axis. The hot material is to flow into the cavity from the module passage 12 through the outlet 13, the chamber and the annular gate space gap.

The third space part of the axial space formed in the frame block 19 defines, in combination with the module 1, an annular space gap 19A extending in a direction of the module axis. The module 1 is thermally insulated from the stationary mold half due to this axial space gap 19A and the ring insulators 33. The back plate block element 20 has an stepped axial through-hole 20A forming a annular shoulder 20B at the side of the hot runner mold 24. The module 1 is disposed axially in both the hole 20A and the third axial space part of the frame block 19 communicating axially therewith, and its annular frange 1A abuts against the annular shoulder 2OB of the block 20. The module 1 is connected to the block 20 at an extension thereof IB by means of a bolt 1C via a positioning block 31. The back plate block element 22 is provided with a locating ring 23 for a nozzle of an injection machine to be incorporated with the mold arrangement. The runner mold 24 is provided with a sprue bush 28 extending axially toward the locating ring 23. 25 denotes a hole for a manifold heater, 26 denotes a

hole for a thermal electrode, and 32 denotes holes for cooling water or medium.

The hot runner mold 24 is disposed in an axial hole 21A of the block 21 and is in contact with the module 1 via a O-ring 11, which prevents leakage of the material, while it abuts against the block 22 via an annular spacer pad 27, so that the runner mold 24 is held within the hole 21A of the block 21 with an annular space gap 2IB formed between the block 21 and the runner mold 24. The runner mold 24 has an runner passage 30 for the hot material through which a nozzle passage and the module passage 12 communicate. 29 denotes a concave end of the runner passage formed in the sprue bush 28, where the nozzle is to be received at a free end thereof. The above mentioned side gate type mold arrangement is assembled with the non-axial tip type module as shown in Figs. 11 to 17 with Fig. 18. The molded article 35 is included in the drawings only to assist in the explanation of the mold cavity and of course is not present in the mold cavity during assembly in actual practice. The module 1 is provided with a casing protector 38, which has a U shaped slit 38A for each non-axial tip 4, as shown in Figs. 11 and 12. The slits 38A are formed by cutting off opposite U shaped wall portions of the casing. The module 1 is partially covered by the protector 38 with the opposite tips 4 being received in the U shaped slits 38A, and the protector 38 is connected to the module 1 by a bolt 39 at a free end thereof. The casing protector 38 is designed so that the non-axial tips 4 do not project from an outer imaginary surface of the cut-off U shaped wall portion.

At an initial stage of the assembling process, using a base 40, the back plate block element 20 resting on the base 40, and the frame block 19 placed thereon are connected to each other by bolts 41. The cavity half blocks 36 is provided with the ring insulator 36B attached thereto in the annular grooves in advance as

shown in Fig. 18. The arrangement of the blocks at this stage is turned so that it rests with the block 19 sitting on the base 40. The cavity half blocks 36 are then disposed in the axial space X of the frame block 19, each in a position farthest from the mold axis as shown in Fig. 14. At this stage, the protected module 1 is disposed in the axial hole of the block 20 and the third space part of the axial space X of the frame block 19 as shown in Fig. 15. Thereafter, the hot runner mold 24 is mounted on the module 1, and then the other back plate block elements 21 and 22 with the locating ring 22 are mounted to assemble the entire back plate block. The above arrangement is turned so that it rests with the block 22 sitting on the base 40 and then the casing protectors 38A are removed from the module 1. Then the opposite cavity half blocks 36 are forced to move toward the exposed module 1 by a distance S, so that they are located in the second space parts of the axial space X, where the non-axial tips 4 are received in the respective side gates 36B. The wedge spacer blocks 37 are forced to enter into the first space part of the axial space X, so that they urge or bias the cavity half blocks 36 against the module in opposite perpendicular directions via the ring insulators 33. Finally, the wedge spacer blocks 37 and the cavity half blocks 36 are connected to the back plate block element 20 by the bolts 42 and 43, respectively.

Referring to Fig. 9, in comparison with Fig. 10, a second embodiment of a mold arrangement with a non-symmetrical module according to the present invention will be explained. The second embodiment comprises a module substantially the same as that of Fig. 10 (the first embodiment) but different in that the module has a single non-axial tip 4, and a mold arrangement substantially the same as that of Fig. 10, but different in that the mold arrangement is of a non-symmetrical form. A corresponding axial space X of the frame

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block 19 has a first to third space parts corresponding to those of Fig. 10, and further a fourth space part where a separate part 34 of a single cavity half block 36 is received with a corresponding ring insulator 33 sandwiched by the module 1 and the separate part 34 therebetween. The separate part 34 acts as an additional part of the frame block 19 to define the third space part with the single cavity half block 36. In this connection, numerals in Fig. 9, the same as those of Fig. 10, denote the same elements of the module and the mold arrangement.

According to the present invention, a mold arrangement may be provided to have a module, having a plurality of tips 4 at one side of the module or both opposite sides thereof as shown in Figs. 19 to 22, incorporated therewith. The tips are arranged along two parallel lines between which the modules are arranged along a central line.

Alternatively, as shown in Fig. 23 a cavity mold half block 36 may have a plurality of cavity halves 36A with side gates 36B defined therein, or as shown in Fig. 24, a stationary mold half may comprise a frame block defining a plurality of axial spaces X. 36C denotes a part of the cavity mold half, which may be an integrated part of the frame block 19 or an extension of either one of the symmetrical cavity half blocks 36.

Figs. 25 and 26 show embodiments of a plurality of modules 1 arranged in line for a plurality of non-axial gates 36B, wherein there is a single runner passage 30 of a hot runner mold branched to communicate with respective module passages 12.

According to the present invention, any one of the above mentioned side gate type mold arrangements incorporated with the respective non-axial tip type modules may have the hot runner mold omitted with some modifications made, as needed.

A non-axial tip type module of the present invention

may be constituted as various embodiments. For example, another embodiment of the module is illustrated in Figs. 27 to 33. The same numerals as those of Figs. 1 to 8 denote substantially equivalent elements of the module. In this .embodiment, the same tip heater 16 as that of the first embodiment as shown in Fig. 6 is provided but omitted in the drawings involved.

A mold cavity with at least one side gate open thereto is necessary in injection-molding of, for example, half of an audio cassette case. According to the present invention, such article can be advantageously produced using the above mentioned side gate type mold arrangement incorporated with the non-axial tip type module. Preferably, the side gate 36B is of a tapered hollow form converging in a perpendicular direction toward the cavity 36A, and the tip 4 of the module 1 tapers toward the cavity as shown in drawings. The tapered tip 4 is preferably received in the tapered side gate 36B with its free end substantially reaching a cavity surface plane P, so that the tapered side gate and the tapered tip .in combination define a considerably small inner opening Y of an annular form at the cavity surface plane P through which opening Y the hot material is forced to flow into the cavity, as shown in an additional enlarged view in Fig. 9.