WO2017129190A1

WO2017129190A1 - Injection moulding system and injection nozzle

Info

Publication number: WO2017129190A1
Application number: PCT/DK2017/050008
Authority: WO
Inventors: Eduard FLYGENRING; Peter Vest FLYGENRING
Original assignee: Flygenring Eduard
Priority date: 2016-01-25
Filing date: 2017-01-17
Publication date: 2017-08-03

Abstract

Injection nozzle for an injection moulding system, the injection nozzle comprising a flange part (33) and an injection nozzle pipe part (34) attached to the flange in one end and with an injection nozzle outlet provided in the distal end of the nozzle pipe part, wherein the flange part and the nozzle pipe part are provided as separate items, which are connected by a threaded connection provided as an external thread on the pipe part (34) and corresponding thread provided in relation to the internal surface of the axially extending bore provided in the in the flange part (33) wherein the corresponding thread is provided by a number of threaded bolts or screws, such as at least one, two, or three or more bolts or screws, having an engaging thread in relation to the thread on the nozzle pipe part, and where said screws (39) or bolts are arranged in the circumference of the axially extending bore of the flange part for engagement of their thread with the thread on the nozzle pipe part (34).

Description

INJECTION MOULDING SYSTEM AND INJECTION NOZZLE

Field of the Invention

The present invention relates to an injection moulding system comprising a hot runner panel and valve means for controlling the injection of molten material from the hot runner panel and into one or more dies.

The present invention also relates to a needle valve as well as nozzle means for a hot runner injection moulding system.

Background of the Invention

It is common practice by injection molding of thermoplastics or like material to provide the discharge orifice to the dies with a needle-valve to avoid formation of a sprue on the article to be produced. The needle-valves are arranged to open and close the discharge orifice when starting or ending of the injection, respectively.

For example, US 4088271 A discloses a needle valve for hot runner injection molding. When starting the injection the needle is retracted from the discharge orifice by the pressure of the molten material against the action of spring means. The spring means will automatically return the needle to the closing position when the pressure ceases. The entire needle valve unit may be inserted, removed and/or adjusted from the backside of the hot runner panel without disassembling the same from the dies or the molding machine. JP-H-07-148176 A describes discloses an injection moulding system comprising a hot runner manifold and, at least one injection nozzle arranged at one side of the manifold. A needle valve assembly comprising a valve housing is arranged at the opposite side of the manifold (compared to the injection nozzle). A valve pin extends out of the valve housing and through the manifold and the injection nozzle. The valve housing comprises a bottom cover having an axial bore for the valve needle, and said bottom cover is held in place in the valve housing from the exterior front end of the valve housing on its periphery by the side wall of the valve housing.

Object of the Invention

Accordingly a broad object of the present invention is to overcome the aforemen- tioned prior art shortcomings by providing an improved needle-valve for hot runner injection molding which as a complete unit may be easily inserted, removed as well as adjusted from the backside of the hot runner panel without disassembling the same from the dies or the molding machine. Another object of the present invention is to provide a needle- valve of the kind referred to which is of a simple and reliable construction.

Another object of the present invention is to provide easy disassembly and/or (re)assembly of a needle valve unit, e.g. during maintenance or repair.

A further object of the invention is to effectively prevent ingress of molten material into the interior of a needle-valve unit and thus preventing that the needle position is stuck in the valve housing when the molten material solidifies. A further object of the invention is to effectively prevent ingress of any molten material flow into the interior moveable parts of a needle-valve unit and thus preventing that solidified particles of the molten material may dislocate the selected end positions of the moveable needle. Yet a further aspect of the present invention is to reduce manufacturing costs of injection nozzles for a needle valve operated injection molding system.

Further, another aspect of the present invention is to reduce the amount of waste materials during production of injection nozzles for a needle valve operated injection molding system. Description of the Invention

To achieve the foregoing and other obvious objects of the invention, both stated and unstated hereinafter, the invention provides an injection moulding system comprising a hot runner panel and valve means for controlling the injection of molten material from the hot runner panel and into one or more dies, wherein the valve system comprises one or more needle valves each having one or more needles, where each said needle extends through one or more distribution channels in the hot runner and through an injection nozzle, which comprises a flange part to which a nozzle pipe part is attached, and said injection nozzle comprises one or more axially extending bores through which one or more needles extend, said injection nozzle extending between a front surface of the hot runner panel and one or more orifices through which molten material is injected into a mould, said injection nozzle being mounted on the opposite side of the hot runner panel in relation to the needle valve,. The system is special in that the injection nozzle has a flange part and a separate nozzle pipe part with an ex- ternal thread, which is connectable to the flange by a threaded connection, and where the threaded connection comprises a number of bolts or screws, such as at least one, two, or three or more bolts or screws, having an opposite thread direction in relation to the thread on the nozzle pipe part, said screws are arranged in the circumference of an axially through going bore of the flange for engagement of their thread with the thread on the nozzle pipe.

The injection nozzle is mounted on the opposite side of the hot runner in relation to the valve housing. The central bore in the flange part is not passing through the flange part. At least one small bore with a reduced radius extends from the rear side of the flange part to the bottom of the axial bore to allow the needle or needles to extend through the axially extending bore(s) of the flange part and corresponding bore(s) in the pipe part. The central bore is thus provided with a bottom which acts as a stop for the pipe part when inserting it into the central bore.

Likewise, the screws are inserted into the flange part in blind ending screw bores extending into the flange from the rear surface thereof. This allows for the nozzle pipe to be attached and securely fastened to the flange part. The central bore as well as the screw bores do preferably not comprise any threading.

Hereby the flange and the pipe part of the nozzle unit can be made from separate piec- es, whereby the amount of waste metal from the production of the injection nozzle can be reduced, which in turn reduces the manufacturing costs of injection nozzles for a needle valve operated injection moulding system.

In addition, this construction ensures that the nozzle pipe is securely mounted in the flange part and the risk of the nozzle pipe loosening grip in the flange part is eliminated or at least significantly reduced.

This also further reduces the risk of leaks of molten material in the connection between the nozzle pipe part and the flange part.

When producing an injection nozzle in one piece, the metal item from which the injection nozzle is produced, e.g. in a cutting operation, such as spin cutting, must be as large as the flange diameter in order to provide the injection nozzle in one piece. This would result in large amounts of waste metal chips, because the diameter of the metal item needs to be reduced significantly on the pipe part in relation to the flange part. This amount of waste chipped metal is reduced to nearly nothing, because the start metal items for the flange as well as for the nozzle pipe part can be provided in dimensions close to the final size used in the injection nozzle.

In addition man-hours and/or machine production time for producing the injection nozzle are reduced significantly.

In addition, the flange part and the nozzle pipe part is preferably manufactured of dif- ferent metallic materials.

For example the nozzle pipe part transfers heat from a heating coil to the molten material flowing inside the injection nozzle. Thus, the pipe part of the injection nozzle would optimally be produced by a metal or a metal alloy with good thermal conductivity, such as copper, or copper alloys, e.g. Amaloy, AMPCO. Alternatively, beryllium copper alloys, acid proof steel, stainless steel or tool steel may be used. Alternatively, the materials used for the flange part mentioned below may be used for the nozzle pipe part as well.

The flange part of the injection requires a certain strength, e.g. because it is used to fastening of the nozzle to the hot runner. Thus, the flange part of the injection nozzle would optimally be produced by a metal or a metal alloy with high strength, preferably having a hardness of at least 25 HRC, such as steel alloys, in particular stainless steel, e.g. stainless steel 316 types, 34CrNiMo6 steel, steel ETG100. Preferably, the needle valve of the system comprises a valve housing part comprising means for opening or closing the valve by moving the needle or needles in axial direction in backward or forward direction, respectively, and wherein said valve housing comprises a bushing provided in the front end of the valve housing part with a front surface of the bushing against the rear surface of the hot runner panel, said bushing having one or more axial bores through which the needle or needles extend.

Hereby the axial bore or bores in the bushing and the pipe part of the injection nozzle acts as a guide for the needle or for each needle when it is moved in forward or backward direction in the needle valve housing.

Further, the bushing is attachable and detachable from the valve housing from the rear end, which allows the bushing to be removed from the valve housing through the rear end of the valve housing without having to detach the valve housing from the hot runner during this operation. This saves a lot of time during maintenance or repair, be- cause the valve housing does not need to be demounted from the hot runner and subsequently re-mounted during maintenance or repair. For example in case the needle(s) are stuck in the bores through which they extend out of the valve housing, i.e. they are stuck in the bore(s) of the bushing. Then the bushing including any stuck needle are simply detached from the valve housing from the rear end, i.e. via, the valve housing interior. A new bushing may also be mounted in the valve housing from the valve housing rear end.

The injection moulding system comprises a hot runner panel with a supply channel for the molten material and one or more distributing channels arranged within the body of the hot runner panel.

Each hot runner panel is provided with one or more nozzle and valve arrangements for controlling the injection of the molten material into one or more dies.

The injection moulding system comprises one or more needle-valves comprising a needle valve housing. The needle valve housing is preferably provided in at least two parts. A valve housing front part is releasibly attachable to a valve housing rear part. The front end valve housing part is arranged between the hot runner panel and a rear panel arranged parallel to the hot runner panel and is inserted from the front side into the rear panel through a bore. The rear end valve housing part may be inserted into the rear panel through the bore from the rear side of the rear panel. The front end and the rear end valve housing parts are attached to each other, e.g. by a threaded connection or a locking ring or similar attachment means.

The rear end valve housing part is provided with a rear end flange, which provides a closure of the valve housing. The front end valve housing part preferably comprises an outer flange arranged at a defined distance from the front end surface. The flange provides a stop, which prevents the front end valve housing part from being retracted through the bore in the rear panel. The front end surface of the valve housing thus rests against the hot runner panel without being attached thereto.

A valve piston is mounted in the valve housing interior co-axially with the first and second valve housing parts. The valve piston is movable in axial direction by means of actuating means to allow for axially moving the needle from a retracted position to an advanced position or vice versa. The movement of the valve piston is preferably actuated by pneumatic actuation means, e.g. by applying pressurized air to selected areas in the valve housing, i.e. in front of the valve piston to retract the needle, i.e. opening the nozzle orifice for injection of molten material into the die, or by applying pressurized air behind the valve piston to advance piston and the needle, i.e. closing the nozzle.

The rear end of the front end valve housing part preferably provides a stop for the valve piston in forward direction.

The needle is arranged in an axial, threaded bore in the valve piston, which extends axially through the valve piston. The needle can thus be inserted into the valve piston from the rear end of the valve housing and is easily exchanged, e.g. in case the needle is defective. The needle is provided with a polygonal bore, in the rear end for adjusting of its position in relation to the piston by insertion of a tool, e.g. an unbraco key/Allen key, with a corresponding polygonal shape. The polygonal bore is e.g. triangular, square, pentagonal or hexagonal in cross section. Hereby the position of the end of the needle is adjustable in relation to the orifice at the front end of the injection nozzle, which provides the valve seat for the needle. The position of the needle after adjusting thereof may be locked by inserting a needle positioning screw in the bore.

Alternatively, a spring may actuate the valve piston to control the opening and closing of the needle valve. A helical spring is then provided in the valve housing interior and surrounds the valve piston as described in US 4088271 A.

The bushing provided in the needle valve housing is thus not attached to the hot runner, e.g. by insertion in a bore provided in the hot runner and attached thereto e.g. by a threaded connection. Instead the bushing is mounted in the valve housing front part only, preferably by means of a thread on the outer surface of the bushing and a corresponding thread in an axial bore in the valve housing front part.

The front end bushing is inserted into the valve housing front part while the valve housing is in position in relation to the hot runner panel as described below. This ensures that the front end bushing is preloaded or prestressed and is firmly positioned in relation to the hot runner panel. This reduces the risk of subsequently bending the needle, in particular during cooling of the hot runner panel. When heating the hot runner panel after having arranged the valve housing and inserting the needle through a cold hot runner, the thermal expansion of the hot runner panel causes a dislocation of the valve housing in relation to the hot runner. When the valve housing is attached to the hot runner panel, e.g. by means of a screw connection, as e.g. in US 4088271 A, this may cause that the needle becomes bended when heating the hot runner panel. This may in turn lead to dislocation of the needle tip, which may rub against the nozzle opening at the nozzle pipe or the opening to the die, which causes wear on the metal around the nozzle opening and a resulting defective closure of the needle valve.

In addition, heating the hot runner panel after mounting of the valve housing, the bushing etc. may result in different thermal expansion of the parts, whereby the front end bushing and the valve housing are no longer flush against each other. This may cause leak of molten material onto the rear surface of the hot runner panel, which leads to loss of molten material and increased production costs. In addition this may lead to increased down time for maintenance, e.g. cleaning, of the hot runner injection moulding system. This is elegantly avoided in the present system.

In addition, air inside the valve housing will cool the front end bushing from the rear end. This will cause an increased viscosity of any molten material present in the axial- ly extending bore(s) surrounding the needle(s) in the front end bushing which even further prevents or reduces ingress of molten material into the valve housing. The air may e.g. enter the valve housing interior through the axial bore(s) in the valve piston, i.e. the bore(s) in which a needle is mounted.

When more than one needle is provided in the valve to simultaneously actuate one or more nozzle orifices injecting molten material into the die or dies, the needles are mounted in the valve piston as described above. Each needle is preferably cooperating with a corresponding axial bore in the bushing. Similarly, each needle may extend through the distribution channel through the hot runner panel or each needle may extend through a corresponding distribution channel. Similarly, the pipe part of the in- jection nozzle may be provided with a single bore surrounding all needles or with an axially extending bore. For each needle, a cooperating orifice into the die is then provided for each needle. The bushing provided in the front end of the valve housing comprises a back flow drainage channel for draining molten material entering the valve housing through the axial bore towards the front surface of the valve housing.

Usually the molten material is supplied to the injection nozzles under pressure by ap- plying a pressure to the molten material before its passage through the hot runner. This results in a risk of a back-flow of molten material, which may enter the valve housing through the central bore, in particular in an interspace between the surface of the needle and the central bore of the bushing. This will result in the needle becoming stuck, when the molten material solidifies in the axial bore and "glues" the needle in a stuck position in the valve housing. This situation results in production stop and the need for clearing the valve housing from any solidified material before production may be resumed.

The back flow drainage channel allows the molten material to escape from the valve housing which effectively eliminates or reduces the risk of the needle becoming stuck in the valve housing.

Preferably, the drainage channel comprises a groove extending in at least a part of the circumference of the axial bore, said groove being in fluid connection with a radially extending bore, and where the outer end of said radially extending bore is in fluid connection with a groove provided in the outer surface of the bushing between the radially extending bore and an opening in the valve housing front end provided in the bushing. Hereby the drainage channel guides any ingress of molten material to the front end of the valve housing. Since the front end of the valve housing is in direct contact with the hot runner the molten material is subjected to temperatures which will burn off the molten material on the hot runner surface. When more than one axial bore is provided a drainage channel may be provided for each axial bore as described above resulting in an opening in the front end of the valve housing for each drainage channel. Alternatively the circumferential groove in each axially extending bore may be in fluid connection with one or more common radially extending channels and one or more corresponding grooves provided in the outer surface of the bushing between the radially extending bore and the corresponding opening in the front end surface of the bushing.

Preferably, the front end of the needle valve housing further comprises one or more grooves and/or protrusions, so as to allow the molten material to be spread on a larger surface of the hot runner exterior surface for improved and fast elimination of the molten material by combustion. In addition, the protrusions and/or grooves ensure that combustion of the molten material does not take place in the isolated area around the opening in the front end of the bushing through which the molten material exits the drainage channel.

The protrusions and/or grooves may e.g. provide a pattern of connected grooves, e.g. as channels between protrusions, on the front end surface of the valve housing, which allows for fast distribution of the molten material over a large surface.

The radius of a rear end of the bushing is preferably reduced and provided in polygonal shape, such as triangular, square pentagonal or hexagonal shape.

Hereby it is possible to insert a tool, e.g. a wrench, a socket wrench or a similar tool, with a complementary shape to enable insertion or removal of the bushing from the valve housing without removing the valve housing from its position against the hot runner. Thus, it becomes possible to arrange the front end bushing from the rear end of the valve housing without removing the entire valve housing, i.e. while the valve housing is arranged in relation to the rear side of hot runner panel or to gain access to the front end bushing of the valve housing from the back end of the valve housing after removal of the valve piston.

In addition, it becomes possible to remove the front end bushing including any nee- dle(s), e.g. in case a needle is stuck in the bushing, e.g. because of the needle is "glued" to the bushing by solidified molten material in the gap between a needle and an axially extending bore in the front end bushing.

The front end bushing is preferably arranged in the valve housing while the hot runner panel is heated to a temperature close to the operating temperature. The front end bushing is tightened against the hot runner, e.g. with a force corresponding to 15-20 Nm. The front end bushing is thus inserted from the rear end of the valve housing before inserting the valve piston and the needle or needles. This ensures that the front end bushing is screwed into position in the valve housing to ensure that the front end surface of the bushing is flush with the rear surface of the hot runner panel. This reduces the risk of leaks and ensures good thermal contact between the valve housing, in particular the front end bushing, and the hot runner panel. This further reduces the risk of ingress of any molten material into the valve housing, which subsequently solidifies around the needle inside the valve housing and thus causes production stops or defec- tively moulded articles caused by a defective needle valve.

The objects of the present invention are also met by providing a needle valve, in particular for an injection moulding system.

The needle valve is generally already described above and comprises a valve housing part with means for opening or closing the valve by moving the needle or needles in axial direction in backward or forward direction, respectively. Said valve housing comprises a front end bushing provided in the front end of the valve housing with a front surface against the rear surface of the hot runner, said bushing having one or more axially extending bores through which the needle(s) extends, and where the front end bushing comprises one or more back flow bleed channels for draining molten material entering the valve housing through the axially extending bores towards the front surface of the valve housing.

As also described above, each drainage channel comprises a groove extending in at least a part of the circumference of the axially extending bore(s), said groove being in fluid connection with a radially extending bore, and where the outer end of said radially extending bore is in fluid connection with a groove provided in the outer surface of the bushing between the radially extending bore and an opening being provided in the front end of the bushing.

As is likewise discussed above, the radius of the rear end of the bushing in the needle valve is reduced and has a polygonal shape.

As also discussed above, the present invention also provides an injection nozzle, in particular for an injection moulding system, as generally discussed above. The injection nozzle comprises a flange part and an injection nozzle pipe part attached to the flange in one end and with an injection nozzle provided in the front end of the nozzle pipe part, wherein the flange part and the nozzle pipe part are provided as separate items, which are connected by a threaded connection provided as an external thread on the pipe part. A corresponding thread is provided in relation to the internal surface of the axially extending bore provided in the flange part.

As also discussed above, the threaded connection in the flange part preferably comprises a number of threaded bolts or screws, such as at least one, two, or three or more bolts or screws, having an engaging thread in relation to the thread on the nozzle pipe part, said screws or bolts are arranged in the circumference of the axially throughgo- ing bore of the flange part for engagement of their thread with the thread on the nozzle pipe part.

Preferably, said axially extending central bore is provided from the front end side of the flange part while said screws or bolts are arranged in blind ending bolt bores provided from the rear side of the flange part. In addition, the bolt bores are arranged to engage with the circumference of the central axially extending bore of the flange part for engagement of their thread with the external thread on the nozzle pipe part. As likewise discussed above the flange part and the nozzle pipe part of the injection nozzle are manufactured of similar or different metallic materials, such as pure metals or metal alloys The above described connection between the nozzle pipe and the flange part of the injection nozzle can be used for assembly of other items, where a rod-shaped item is connected to a plate-shaped member. The connection between the flange and the nozzle pipe is also applicable for assembly of an item comprising a rod-shaped member, such as a pipe element, and a plate or substantially plate-shaped member, such as a flange element for a pipe, wherein the plate-shaped member and the rod-shaped member are provided as separate discrete parts, said connection comprising a threaded connection provided as an external thread on one end area of the rod-shaped member and a thread provided in the internal surface of a bore provided to extend into, but not through the plate-shaped member, wherein the threaded connection in the internal surface of the bore comprises a number of threaded bolts or screws, such as at least one, two, or three or more bolts or screws, having an opposite thread direction in relation to the thread on the cylindrical element, said screws or bolts being arranged in bolt bores provided from the reverse side of the plate-shaped member and arranged to engage with the circumference of the bore of the plate-shaped member for engagement of their thread with the thread on the rod-shaped member.

Description of the Drawing

The present invention will be described in detail with reference to the drawings in which

Fig. 1 shows a cross sectional view of a hot runner in an injection moulding system comprising needle valves and injection nozzles according to the present invention

Fig. 2-3 show a perspective view and a cross sectional view, respectively, of a needle valve unit according to the present invention

Fig. 4-5 show a perspective view and a cross sectional view, respectively, of the front end bushing of a needle valve unit according to the present invention

Fig. 6-7 show a perspective view and a cross sectional view, respectively, of a hot runner injection nozzle according to the present invention

Fig. 8 shows an end view of a hot runner injection nozzle according to the present invention, and Fig. 9 shows an end view of the a needle valve unit according to the present invention

Detailed Description of the Invention

The present invention is illustrated generally in Fig. 1. A hot runner panel 1 is provid- ed with a supply channel 2 for the molten material and one or more distributing channels 3 arranged within the body of the hot runner panel 1.

Each hot runner panel 1 is provided with one or more nozzle and valve arrangements for controlling the injection of the molten material into a die 4.

In Fig. 1 four nozzle and needle valve arrangements are shown as an example. The left half of Fig. 1 illustrates one way of mounting the injection nozzles Sa, while the right half illustrates a second way of mounting injection nozzles 5b in a hot runner 1. A single nozzle and valve arrangement may be provided on the hot runner 1 for a single die or a number of nozzle and valve arrangements may be arranged in the hot runner 1 in connection with a die comprising one or more moulding cavities (not shown).

In Fig. 1 four nozzle and valve arrangements are illustrated, which may provide mol- ten material to one, two three or four dies or to the corresponding number of cavities in a single die. It is understood that he number of nozzle and valve arrangements may be adapted to the number of dies, die cavities and/or the size of the die(s) to provide optimized injection of the molten material in relation to the size, shape or similar properties of the object(s) produced in the die(s).

In a part of a die 4 there may be provided an orifice 9 for injection of the molten material into a cavity of the die 4. The molten material is supplied under high pressure through the supply pipe 2, the distributing channel 3 and an injection nozzle 5. Co-axially with the injection nozzle 5a-5b a needle-valve unit 8 is provided on the reverse side or the back side of the hot runner panel 1. The needle valve unit 8 rests with the front end against the hot runner panel 1. The needle valve unit 8 does not need to be attached to the hot runner panel 1 by any means. It is held in position by the valve housing being attached to a rear panel la of a hot runner assembly.

By adjustment of the needle 10 position in relation to the orifice 9, the forward end the needle 10 flushes with the orifice 9 of the die 4 when the injection nozzle is in the closed position. The needle valve unit 8 and parts thereof are shown in Figs. 1-5, see especially Figs. 2-3. The needle valve unit comprises the needle 10 which is arranged with the rear end in a valve piston 15 provided in the valve housing 11,13. The needle 10 is locked in the valve piston 15 with a needle positioning screw 24 as discussed further below. The front part valve housing 11 has a central bore 16 in which the needle 10 is arranged to extend through the front end of the valve housing 11 in order to extend through the hot runner panel 1 and the injection nozzle 5 to the orifice 9. The needle 10 thus extends through a part of that distributing channel 3 arranged within the body of the hot runner panel 1 , which distributes molten material to the injection nozzle 5.

The movement of the valve piston 15 is preferably actuated by pneumatic actuation means (not shown). The pneumatic actuation means provide pressurized air to selected areas in the valve housing, i.e. in the free space 16a and/or 16b in front of the valve piston 15 to retract the needle, i.e. opening the nozzle orifice for injection of molten material into the die, or by applying pressurized air behind the valve piston in free space 16c to advance the piston and the needle 10, i.e. closing the nozzle orifice 9.

The rear end of the front end valve housing part 11 preferably provides a stop for the valve piston 15 in forward direction when being pneumatically actuated to provide a forward movement in axial direction by applying pressurized air to free space 16c behind the valve piston 15.

Alternatively, the opening and closing of the needle valve is controlled by a helical spring (not shown) surrounding the valve piston 15 as described in US 4088271 A. The needle 10 comprises a thread 28 on the exterior surface of its rearward end. In the rearward surface of the needle a bore with polygonal cross-section is provided so that it may be operated by means of a polygonal key. The needle 10 is arranged for being attached to the valve piston 15 by being inserted into an axially extending bore 21 provided with a threading in the bore 21. The needle 10 is inserted into the bore 21 from the rear end of the valve piston 15. The rear end 10a of the needle 10 comprises an external threading 22, which engages with the threading provided in the bore 21 in the valve piston 15. A polygonal bore 23 is pro- vided in the rear end surface of the needle to allow the needle to be screwed into the desired position in axial position in relation to the valve piston 15.

The desired position of the needle 10 is determined by the needle tip position relative to the nozzle orifice 9 to ensure that the nozzle is properly closed when the needle valve 8 is in the closed position. The position of the needle 10 is adjusted by screwing the needle further into the central bore 21 or further out thereof by inserting a tool, e.g. an Alien key/unbraco key into the polygonal bore in the end of the needle 10. The rear side of the valve housing is shown in Fig. 9. To assist in positioning of the needle's 10 tip a scale 47 is provided. For example when rotating the needle one division on the scale, the needle may e.g. be forwarded or retracted 0.1 mm depending on the direction of rotation.

The needle position is preferably locked by a needle positioning screw 24, which may also be arranged in the axial bore 21 of the valve piston 15. The needle positioning screw 24 may also be screwed into the axial bore 21 by means of a polygonal key, e.g. an Allen key/unbraco key as described for the needle 10 above.

The front end bushing 20 provided in the front end of the valve housing front part 11 is best seen in Figs. 2-5. The front end bushing 20 comprises a back flow drainage channel for draining molten material entering the valve housing 8 through the axial bore 25 towards the front surface of the valve housing 8.

Preferably, the back flow drainage channel comprises a groove 29 extending in at least a part of the circumference of the axial bore 25, said groove 29 being in fluid connec- lion with a radially extending bore 28. The outer end of said radially extending bore 28 is in fluid connection with a groove 30 provided in the outer surface of the bushing 20 between the radially extending bore 28 and an opening 31 in the valve housing front end provided in the bushing.

Preferably, the front end of the needle valve housing further comprises one or more grooves and/or protrusions 32, so as to allow the molten material to be spread on a larger surface of the hot runner exterior surface for improved and fast elimination of the molten material by combustion.

The protrusions and/or grooves 32 may e.g. provide a pattern of connected grooves, e.g. as channels between protrusions, on the end front end surface of the valve housing, which allows for fast distribution of the molten material over a large surface, see e.g. Fig. 2, where a number of circular and radial channels are provided.

The radius of a rear end of the front end bushing 20 is preferably reduced and provided in polygonal shape, such as triangular, square pentagonal or hexagonal shape in order to be able to insert a tool, e.g. a wrench, a socket wrench or a similar tool (not shown), with a complementary shape through the rear end of the valve housing to en- able insertion or removal of the bushing 20 from the valve housing without removing the valve housing from its position against the hot runner.

In case a backflow of molten material results in that the needle 10 is stuck inside the bushing 20, the needle 10 and the bushing 20 is easily removed from the rear end of the valve part after removing the rear flange 17 and the valve piston 15. The bushing 20 can be taken out of the valve housing by screwing by using a polygonal wrench, e.g. a pipe shaped polygonal wrench, which grips the polygonal rear end of the bushing. Similarly, a new bushing 20 is easily inserted (as described above) into the needle valve housing 8 without needing to disassemble the needle valve housing part 8 from the hot runner panel 1.

The injection nozzle 5 is shown in Figs. 6-8. The injection nozzle 5 is mounted on the front side, i.e. the opposite side of the hot runner 1 in relation to the valve unit 8. The injection nozzle 5 is attached as an axial extension of the needle valve unit 8 to allow the needle 10 to extend through a central bore 36 in the injection nozzle. The orifice 9 in the front of the nozzle valve is intended to act as a valve seat for the tip of the needle 10 to allow opening and closing of the needle valve. The injection nozzle 5 comprises a flange part 33 provided with an axial central bore 36a. At least a part of the central bore 36a is optionally provided with an internal thread 37. The central bore 36 in the flange part is not passing through the flange part. A small bore 36b with a reduced radius extends from the rear side of the flange part 3 to the bottom of the central bore 36a to allow the needle to extend through the central bores 36, 36a of the flange part 33 and the pipe part 34. The central bore 36a is thus provided with shoulders which act as a stop for the pipe part when inserting it into the central bore.

A separate nozzle pipe part 34 is provided with an orifice 9 in the front end and exter- nal thread 38 at a rear end of the pipe part 34. The external thread 38 is provided to grip into the optional internal thread 37 in the central bore 36a of the flange part 33.

The threaded connection between the flange and the pipe parts comprises a number of mounting bolts or screws 39, such as at least one, two, or three or more bolts or screws 39. The bolts or screws 39 (also just mentioned as screws) are provided with a polygonal bore in the end surface which is visible, when the screws 39 are mounted in the injection nozzle to allow for easy turning thereof. The mounting screws' threads 41 are provided to engage with the thread 38 on the nozzle pipe part 34. Thus, the depth and the pitch of the thread 41 on the screws 39 correspond to the depth and the pitch of the thread 38 on the nozzle pipe part 34. The screws 39 are arranged in the circumference of the axially throughgoing bore of the flange for engagement of their thread with the thread 38 on the nozzle pipe 34 by providing blind ending screw bores from the rear side of the flange part 33. Hereby the flange part 33 and the pipe part 34 can be made from separate pieces and subsequently assembled into an injection nozzle as also described above.

When attaching the flange part 33 to the pipe part 34, the external thread 38 on the pipe part 34 is inserted into the central bore 36a of the flange part 33. The screws 39 are inserted into screw bores 43 from the rear end side of the flange part 33. The screw bores 43 are positioned in relation to the central bore 36a in the flange so as to allow the screw threads 41 to extend into the central bore 36a. This allows the screw thread 41 to engage with the external threading 38 on the pipe part 34. The pipe part is screwed into the flange while also operating at least one of the screws 39 in the reverse direction. This allows for fast and easy attachment of the pipe part 34 in the flange part 33.

The flange part 33 and the nozzle pipe part 34 are preferably manufactured of differ- ent metallic materials. For example the nozzle pipe part 34 transfers heat from a heating coil 35 to the molten material flowing inside the bore 36 of the injection nozzle 5. Therefore, the pipe part is preferably made of a metal or a metal alloy with good thermal conductivity, such as Amaloy or materials as mentioned above. The flange part 33 of the injection nozzle requires a certain strength, e.g. because it is used for fastening the nozzle to the hot runner 1. Thus, the flange part 33 of the injection nozzle 5 would optimally be produced by a metal or a metal alloy with high strength, typically having a hardness of at least 25 HRC, such as steel alloys, in particular stainless steel, e.g. stainless steel 316 types as also discussed above.

As seen in Fig. 1, the injection nozzle 5 is mounted between the hot runner panel 1 and the die 4. The flange part 33 comprises a shoulder 44 on the outer circumference thereof which rests against the rear surface of the dies as shown on the left half of Fig. 1. The nozzle pipe 34 is inserted into a bore 45 in the die 4 to provide the orifice 9 inlet to the molding cavity of the die 4.

Alternatively, as shown in the right half part of Fig 1, the shoulder 44 rests against a pipe bushing 46 arranged in the bore 45 of the die 4. An exchangeable nozzle bushing 47 is provided in the bore 45 to surround the front end of the nozzle pipe part 34 and provides the orifice 9 to the inlet to the molding cavity of the die 4. The exchangeable nozzle bushing 47 rests on a shoulder 48 provided in the circumference of the bore 45. In case the orifice 9 is defective, e.g. caused by a warped needle acting against the material surrounding the orifice 9. Then the exchangeable nozzle bushing 47 needs only to be removed and a new inserted. The pipe bushing 46 is arranged on the rear side of the exchangeable nozzle bushing 47 in the bore 45. Thus, a defective nozzle orifice 9 is easily repaired without needing to exchange the entire die 4.

As also mentioned above, the attachment means used to attach the pipe part to the flange part is also applicable for attaching a generally rod-shaped member to a generally plate-shaped member. The attachment method is mentioned above and may e.g. also be applicable for attaching legs of a chair to a chair seat. The central bore is then applied from a first side of the plate member and the screw bores are applied from the reverse side of the plate member.

The "front side", "front surface", "front end" is defined as the side which faces towards the die or dies 4 when seen in axial direction of the nozzle 5 and/or the needle valve unit 8. Similarly, the "rear side", "rear surface", "rear end" is defined as the side which faces away from the die or dies 4.

Further modifications and alternative embodiments of the invention will be evident to those skilled in the art in view of this description. Various changes may be made in the shape, size and arrangement of parts. The parts arranged for being operated by a polygonal key may be arranged for being operated by other forms of tools e.g. screwdrivers where applicable.

Claims

CLAIMS 1. Injection moulding system comprising a hot runner panel and valve means for controlling the injection of molten material from the hot runner panel and into one or more dies, wherein the valve system comprises one or more needle valves each having one or more needles, said needle(s) extending through one or more distribution channels in the hot runner panel and through an injection nozzle, which comprises a flange part to which a nozzle pipe part is attached, and said injection nozzle comprises one or more axially extending bore(s) through which the needle(s) extend, said injection noz- zle extending between a front surface of the hot runner panel and one or more orifices through which molten material is injected into a mould, said injection nozzle is mounted on the opposite side of the hot runner panel in relation to the needle valve, and wherein the injection nozzle has a flange part and a separate nozzle pipe part with an external thread, which is connectable to the flange by a threaded connection, and where the threaded connection comprises a number of bolts or screws, such as at least one, two, or three or more bolts or screws, having an opposite thread direction in relation to the thread on the nozzle pipe part, said screws are arranged in the circumference of an axially through going bore of the flange for engagement of their thread with the thread on the nozzle pipe part.

2. Injection moulding system according to claim 1, characterized in that the needle valve comprises a valve housing part comprising means for opening or closing the valve by moving the needle(s) in axial direction in backward or forward direction, respectively, and wherein said valve housing comprises a bushing provided in the front end of the valve housing with a front surface towards the rear surface of the hot runner panel, said bushing having one or more axial bores through which the needle or needles extend.

3. Injection moulding system according to claim 1 or 2, characterized in that the front end surface of the valve housing rests against the rear surface of the hot runner panel without being attached thereto.

4. Injection moulding system according to any of the claims 1-3, characterized in that the bushing comprises a back flow drainage channel for draining molten material en- lering the valve housing through the at least one axial bore(s) towards the front surface of the valve housing.

5. Injection moulding system according to claim 4, characterized in that the drainage channel comprises a groove extending in at least a part of the circumference of axial bore or bores, each groove being in fluid connection with a radially extending bore, and where the outer end of said radially extending bore is in fluid connection with a groove provided in the outer surface of the bushing between the radially extending bore and an opening in the valve housing front end provided in the bushing.

6. Injection moulding system according to any of the preceding claims, characterized in that the radius of a rear end of the bushing is reduced and has a polygonal shape.

7. Injection moulding system according to any of the preceding claims, characterized in that the injection nozzle has a flange part and a separate nozzle pipe part with an external thread, which is connectable to the flange by a threaded connection, and where the threaded connection comprises a number of bolts or screws, such as at least one, two, or three or more bolts or screws, having an opposite thread direction in relation to the thread on the nozzle pipe part, said screws are arranged in the circumfer- ence of an axially through going bore of the flange for engagement of their thread with the thread on the nozzle pipe.

8. Injection nozzle, for an injection moulding system according to any of claims 1-7, comprising a flange part and an injection nozzle pipe part attached to the flange in one end and with an injection nozzle outlet provided in the distal end of the nozzle pipe part, wherein the flange part and the nozzle pipe part are provided as separate items, which are connected by a threaded connection provided as an external thread on the pipe part and corresponding thread provided in relation to the internal surface of the axially extending bore provided in the in the flange part characterized in that the cor- responding thread is provided by a number of threaded bolts or screws, such as at least one, two, or three or more bolts or screws, having an engaging thread in relation to the thread on the nozzle pipe part, and where said screws or bolts are arranged in the circumference of the axially extending bore of the flange part for engagement of their thread with the thread on the nozzle pipe part.

9. Injection nozzle, according lo claim 8, characterized in that the flange part and the nozzle pipe part are manufactured of the similar or different metallic materials, such as pure metals or metal alloys.

10. Needle valve, in particular for an injection moulding system, comprising a valve housing part comprising means for opening or closing the valve by moving one or more needles in axial direction in backward or forward direction, respectively, and wherein said valve housing comprises a bushing provided in the front end of the valve housing with a front surface of the bushing against the rear surface of the hot runner, said bushing having one or more axial bores through which the needle(s) extend, and where the bushing comprises a back flow bleed channel for draining molten material entering the valve housing through the axial bore(s) towards the front surface of the valve housing.

11. Needle valve according to claim 10, characterized in that the drainage channel or each drainage channel comprises a groove extending in at least a part of the circumference of the axial bore(s), said groove(s) being in fluid connection with a radially extending bore, and where the outer end of said radially extending bore is in fluid connection with a groove provided in the outer surface of the bushing between the radially extending bore and an opening being provided in the front end of the bushing.

12. Needle valve according to claim 10 or 11, characterized in that the radius of a rear end of the bushing is reduced and has a polygonal shape.