Abstract:
In-line valve-gated nozzles for a single or multiple cavity applications wherein a valve-gated hot runner nozzle has a melt channel uniformly heated along the entire path. The valve pin is driven by an actuation device that is located adjacent to the nozzle to regulate the flow of melt. The actuation device has a linear motion and applies a uniform axial pressure on to the valve pin. This valve-gated nozzle can be linked directly to a machine nozzle, to an injection manifold or to a stack mold.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority under 35 U.S.C. § 119(e) to Provisional Application No. 60/363,891 filed Mar. 14, 2002, the contents of which are incorporated in their entirety by reference herein. 
     
    
     
       STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT  
         [0002]    Not applicable.  
         REFERENCE TO MICROFICHE APPENDIX/SEQUENCE LISTING/TABLE/COMPUTER PROGRAM LISTING APPENDIX (SUBMITTED ON A COMPACT DISC AND AN INCORPORATION-BY-REFERENCE OF THE MATERIAL ON THE COMPACT DISC)  
         [0003]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0004]    1. Field of the Invention  
           [0005]    This invention relates to valve-gated injection molding systems and, in particular, those systems in which an actuator is positioned laterally from an injection nozzle body.  
           [0006]    2. Related Art  
           [0007]    Valve-gated injection molding systems conventionally include a valve pin disposed in a nozzle melt channel. The valve pin extends through the manifold melt channel to a double acting air-operated piston which moves the valve pin into and out of a position that blocks the nozzle outlet. Such a conventional system can be seen, for example, in U.S. Pat. No. 4,173,448 to Rees et al. and in FIG. 8 of the drawings provided herewith. In this type of conventional system, the actuator is mounted in a plate upstream of the manifold. Such a conventional system has certain disadvantages. For example, the actuator located on top of the manifold increases the height of the overall system. Further, the valve pin is long, which increases the risk of breakage, bending, and/or misalignment within the melt channel. Still further, because the valve pin extends through the heated nozzle and the heated manifold, it is exposed to the expansion and contraction and relative movement of those parts. This further increases the risk that the valve pin may bend or become misaligned in the melt channel. Further, in systems with a large amount of mold cavities, there is greater risk of inconsistency between the different valve pins due to this bending or misalignment. Another problem with this type of valve-gated injection molding system is that melt from the manifold melt channel tends to leak up towards the piston assembly. Seals are required around the valve pin above the manifold to stop the leakage.  
           [0008]    Other conventional systems attempt to address some of these problems. For example, U.S. Pat. No. 4,919,606 to Gellert discloses a valve-gated injection molding system wherein a cylinder and piston assembly is located to a side of the manifold. The movement of the piston is translated to the valve pin through a rack and pinion arrangement. This type of arrangement addresses the height of the overall system and the length of the valve pins. However, this system is expensive to manufacture as it uses highly accurate components. Other similar systems also move the piston assembly adjacent to the manifold or the nozzle and translate the movement of the piston laterally to actuate the valve pin, such as in shown in U.S. Pat. Nos. 5,902,614; 5,916,605; and 5,984,661. These types of arrangements suffer from difficulty in transferring axially the necessary force from the piston assembly to the valve pin. They also include bends in the nozzle melt channel that are not heated in order to allow access to the valve pin from a lateral position.  
           [0009]    Another conventional system includes an annular slidable piston member which surrounds the nozzle and is known as an “in-line annular piston valve gated nozzle”. Due to a connection between a slidable member and a valve pin, vertical motion of the slidable member causes the vertical motion of the valve pin. Such a system can be seen in U.S. Pat. Nos. 3,677,682 and 6,159,000, for example. In such systems, the slidable member is often too close to the nozzle body and is therefore subject to high temperatures which can degrade components thereof, such as annular sealing members (i.e. O-ring seals). Also, many of such systems are complicated and/or expensive to manufacture and require the use of special heat resistant materials. Furthermore, many of such systems do not have heaters or heater components for applying heat to that portion of the melt channel around which the slidable member is slidable. In those systems which do have heaters for heating such a portion of the melt channel, the heaters are often not evenly radially spaced from the melt channel, i.e. are asymmetrical relative to the melt channel, thereby resulting in either too much or too little heat being applied to melt flowing therethrough.  
         SUMMARY OF THE INVENTION  
         [0010]    Due to the disadvantages noted above, there is a need for a valve-gated injection molding system wherein the nozzle melt channel is uniformly heated along its entire path, the actuator assembly is located adjacent or below the manifold, and the actuator actuates the valve pin axially without a lateral translation of the force such that sufficient force can be applied to the valve pin. Further, a relatively short valve pin that does not extend through multiple parts of the molding system is desirable.  
           [0011]    The present invention addresses the above-noted disadvantages of conventional systems by providing an injection molding system including a nozzle body, an actuator, and a valve pin coupled to the actuator. The nozzle body includes an inlet, an outlet, and a melt channel extending from the inlet to the outlet. The outlet of the nozzle body is disposed about a first axis. The melt channel of the nozzle body includes an end portion located adjacent to the outlet and disposed about the first axis. The nozzle body also includes an offset body portion located between the inlet and the end portion that is laterally offset relative to the first axis. The actuator is disposed external to and positioned laterally from the offset body portion of the nozzle body. The actuator is disposed in a housing and includes an axial translation member located and slidable in the housing co-axially with the first axis. The valve pin is coupled to the actuator and extends along the first axis. A tip portion of the valve pin is positioned in the end portion of the nozzle body and is movable under the influence of the axial translation member between a first position in which the tip portion is clear of the outlet and a second position in which the tip portion is blocking the outlet to stop the flow of melt therethrough. The system further includes a heater disposed around the offset body portion and the end portion of the nozzle body.  
           [0012]    Embodiments according to the present invention address the disadvantages in the prior art discussed above. Because the actuating member of the valve pin is located adjacent to the nozzle body, the overall height of the system and the length of the valve pin are minimized. The reduced length of the valve pin minimizes the risk that the valve pin will break, bend, or become misaligned during use. Further, the valve pin travels through fewer independent parts of the molding machine which, in turn, minimizes the problems associated with thermal expansion of those parts and the consequent misalignment thereof. Further, application of a force on the valve pin evenly distributed about the valve pin axis also reduces the chance that the valve pin will deviate from movement along that axis. Such deviation may lead to lateral forces on the pin which may increase the risk of breakage and leak of molten material. In one embodiment the actuation means delivers only a translation movement which is directly and coaxially transmitted to the valve pin.  
           [0013]    Further, the actuating member of the present invention is separate from the nozzle body, which reduces exposure of the piston seals to heat. The present invention also includes a nozzle heater that is disposed symmetrically relative to the melt channel, thereby resulting in an even heat distribution. Any suitable heater can be used, however preferably embedded or film heaters are used to reduce the size of the nozzle.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES  
       [0014]    To better understand the invention, preferred embodiments will now be described with reference to the following drawings.  
         [0015]    [0015]FIG. 1 is a schematic sectional view of a valve-actuated injection molding system according to an embodiment of the invention having a single injection nozzle and a co-axial double piston actuator associated therewith.  
         [0016]    [0016]FIG. 1 a  is a cross-sectional view along line A-A of FIG. 1.  
         [0017]    [0017]FIG. 2 is a schematic sectional view of a valve-actuated injection molding system according to another embodiment having a single injection nozzle with an off-centre single piston actuator associated therewith.  
         [0018]    [0018]FIG. 3 is a schematic sectional view of a valve-actuated injection molding system according to another embodiment having a plurality of valve-gated injection nozzles and a corresponding plurality of co-axial single piston actuator components associated therewith.  
         [0019]    [0019]FIG. 4 is a schematic sectional view of a valve-actuated injection molding system according to another embodiment having a single bifurcated injection nozzle with a plurality of co-axial single piston actuator components associated therewith.  
         [0020]    [0020]FIG. 5 a  is a schematic sectional view of a valve-actuated injection molding system according to another embodiment having a plurality of injection nozzles and a single off-centre double piston actuator component carrying a plurality of valve pins associated therewith.  
         [0021]    [0021]FIG. 5 b  is a schematic axial view of a manifold melt passageway of the embodiment of FIG. 5 a.    
         [0022]    [0022]FIG. 6 a  is a schematic sectional view of a valve-actuated injection molding system according to another embodiment having a single injection nozzle and a bladder actuator associated therewith, the bladder actuator having a bladder shown in an expanded condition.  
         [0023]    [0023]FIG. 6 b  is a schematic sectional view of the valve-actuated injection molding system of FIG. 6 a  in which the bladder is in a collapsed condition.  
         [0024]    [0024]FIG. 6 c  is an enlarged view of the area designated by reference numeral  6   c  in FIG. 6 b.    
         [0025]    [0025]FIG. 7 is a schematic sectional view of a valve-actuated injection molding system according to another embodiment of the invention having a valve pin positionable in a melt channel of an injection nozzle adjacent to and upstream of an outlet of the nozzle to block the flow of melt through the outlet.  
         [0026]    [0026]FIG. 8 is a schematic sectional view of a prior art valve-actuated injection molding system in which pistons are mounted in a mounting plate upstream of the manifold. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    Preferred embodiments of the present invention are now described with reference to the figures where like reference numbers indicate identical or functionally similar elements. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention.  
         [0028]    [0028]FIG. 1 depicts a valve-gated injection molding system  20  according to an embodiment of the invention. FIG. 1 a  shows a cross-section along line A-A of FIG. 1. The system  20  includes an elongated hot runner injection nozzle designated generally by reference numeral  22  having an elongated nozzle body  24 . The nozzle body  24  has an inlet  26  coupled to machine nozzle  28  which discharges hot pressurized melt. Melt from the machine nozzle  28  travels through an inlet channel  30  defined by a hot runner nozzle head  32  into the inlet  26  of the nozzle body  24 . The nozzle body  24  further includes an outlet  34  and defines a melt channel  36  extending between the inlet  26  and the outlet  34  through which melt flows. The melt is discharged from the outlet  34  through a mold gate  38  and into a mold cavity  40  to form the molded product. Cooling channels  41  are provided in a mold platen (not shown) to dissipate heat transferred from the nozzle body  24  to the mold platen and to freeze the mold gate  38 , as is known in the art of injection molding.  
         [0029]    As can be seen in the drawing, the melt channel  36  has an end portion  42  for receiving a tip portion of a valve pin as will be described further below. The end portion  42  is located adjacent to the outlet  34  and disposed about a first axis  44  about which the machine nozzle  28  and outlet  34  are also disposed, according to one aspect of the invention. The nozzle body  24  has an offset portion  46  located between the inlet  26  and the end portion  32 . The nozzle body  24  further has an outlet or nozzle tip portion  48  defining the end portion  42  and a bridge portion  50  which connects the offset portion  46  to the outlet or nozzle tip portion  48 .  
         [0030]    The system  20  further includes a co-axial pneumatic double piston actuator, designated generally by reference numeral  52 , operable to move a valve pin  53  between a first position in which a tip portion  55  of the valve pin  53 , positioned in the end portion  42 , is clear of the outlet  34 , and a second position in which the tip portion  55  is blocking the outlet  34  to stop the flow of melt therethrough. According to another aspect of the invention, only one piston, such as  66 , can be used in certain molding conditions. The actuator  52  is external to and positioned laterally from the offset portion  46  of the nozzle body  24 , and has a closed cylindrical housing  54  secured to the nozzle head  32  by bolts  64 . The housing  54  includes a cylindrical wall  56  which has an inner cylindrical surface  58  defined about a second axis which, in this embodiment, is co-axial with the first axis  44 . The housing  54  further includes a pair of opposed, transversely-extending circular end walls  60 ,  62  at respective ends of the cylindrical wall  56  and a transversely-extending partition wall  72  between the end walls  60 ,  62  to divide the housing into two compartments  57 ,  59 .  
         [0031]    Located inside the housing  54  is a displaceable member which, in this embodiment, are slidable members in the form of first and second cylindrical pistons  66 ,  68  located one in each compartment  57 ,  59  and linked together by the valve pin  53  for movement in unison. The pistons  66 ,  68  have outer surfaces which mate with and slide within the inner cylindrical surface  58  coaxially with the first axis. Also inside the housing  54  is an axial translation member in the form of a connector pin  69  integrally formed and co-axial with the valve pin  53 . The connector pin  69  is co-axial with the first axis  44  and slidable with the pistons  66 ,  68  in the housing  54 . Seen in accordance with another aspect of the invention, the system  20  has an axial translation member having a portion  69  located and slidable in the housing  54  along the first axis  44  and a co-axial valve pin portion  53  extending into the nozzle body  24 . The following description, however, will be with reference to the first described aspect of the invention and the person skilled in the art will understand how the description may be modified to accord with said other aspect.  
         [0032]    The connector pin  69  extends through an opening in the partition wall  72  and then through a tubular valve pin guide  74  which is positioned around a central opening in the end wall  62 . The valve pin guide  74  is dimensioned to receive and guide the valve pin  53  out of the housing  54  along the first axis  44 . From there, the valve pin  53  enters a valve pin bushing  76  seated in an opening in the outlet portion  48  of the nozzle body  22 . The valve pin bushing  76  is positioned and dimensioned to slidably receive and guide the valve pin  53  axially into the end portion  42 .  
         [0033]    To move the pistons  66 ,  68 , and therefore the tip portion  55  into and out of the outlet  34 , pressurized fluid, which in this embodiment is pressurized air, is selectively and alternately discharged into the compartments  57 ,  59  inside the housing  54 . To do this, the actuator  52  includes first and second fluid inlets  80 ,  82  extending through the cylindrical wall  56  of the housing  54  into the compartment  57 , one to each side of the first piston  66 , and third and fourth inlets  84 ,  86  extending through the cylindrical wall  56  into the compartment  59 , one to each side of the second piston  68 . The first piston  66  is moveable between the first and second inlets  80 ,  82  and the second piston  68  is moveable between the third and fourth inlets  84 ,  86 . The inlets  80 ,  82 ,  84 ,  86  are coupled to a mechanism (as is known in the art and not shown) which alternately supplies the first and third inlets  80 ,  84  and the second and fourth inlets  82 ,  86  with pressurized air to alternately move the pistons  66 ,  68  in first and second directions designated by arrows  88 ,  90 , respectively. As the pistons  66 ,  68  move in the first direction  88 , the valve pin  53  is moved to the second position in which the tip portion  55  is blocking the outlet  34  thereby preventing melt to flow therethrough. When the pistons  66 ,  68  move in the second direction  90 , the tip portion  55  is moved to the first position in which it is clear of the outlet  34 .  
         [0034]    The system  20  has features for minimizing leakage of pressurized air and melt. Both the valve pin guide  74  and valve pin bushing  76  define cylindrical passageways large enough to permit the valve pin  53  to slide axially therethrough but not so large as to allow excessive leakage of air and melt from inside the housing  54  and nozzle body  24 , respectively. To minimize excessive gas leakage of air from one space into another space within each compartment  57 ,  59 , the pistons  66 ,  68  have circumferentially grooved surfaces in which are positioned heat-resistant O-ring seals  92 . Because the valve pin  53  and connector pin  69  extend along the axis of the cylindrical pistons  66 ,  68 , the actuator  52  is effective in applying a force to the valve pin  53  which is evenly distributed about the first axis  44 . This gives rise to advantages which will later be discussed.  
         [0035]    To maintain the temperature of the melt as it travels through the melt channel  36  in a molten state and within a predetermined desired temperature range, the system  20  has a coiled heater  94  embedded the nozzle body  24  and surrounding the melt channel  36 . Heater  94  provides heat energy to melt channel  36 , as represented by arrow  93  in FIG. 1 a.  In this embodiment, the heater  94  has a first end proximate the inlet  26  and a second end proximate the outlet  34 . Thus, the heater has a heater portion which is attached to the offset portion  46  of the nozzle body  24 , which heater portion is positioned coaxially relative to the portion of the melt channel  36  extending through the offset portion  36  about an axis  96 . Cartridge heaters or film heaters can be used for both sections, and if the space is not a concern, band or clamp heaters can also be used.  
         [0036]    Referring now to FIG. 2, a valve-gated injection molding system according to a second embodiment of the invention, designated generally by reference numeral  120 , is shown. The system  120  is similar to the system  20  in many respects. Thus, for the sake of clarity, like reference numerals have been used to refer to like parts. For the sake of convenience, only the differences relative to the first embodiment  20  will be discussed in detail.  
         [0037]    The system  120  utilizes an off-set single piston actuator  52   a  having a housing  54   a  with a larger lateral dimension than the housing  54  of the system  20 . Thus, the first described system  20  is preferred if lateral space is restricted. The present embodiment is slightly simpler in design and therefore preferred if space permits.  
         [0038]    Similar to the system  20 , the system  120  has a hot runner nozzle body  24  having an inlet  26  to be coupled to a source of pressurized melt discharged by a machine nozzle (not shown). The nozzle body  24  also has an outlet  34  disposed about a first axis  44 , the nozzle body  24  defining a melt channel  36  extending from the inlet  26  to the outlet  34 . The melt channel has an end portion  42  located adjacent to the outlet  34  and disposed about the first axis  44 . The nozzle body  24  also has an offset body portion  46  located between the inlet  26  and the end portion  42  and being laterally offset relative to the first axis  44 .  
         [0039]    The actuator  52   a  is external to and positioned laterally from the nozzle body  24  relative to the first axis  44 . The actuator has a closed cylindrical housing  54   a  attached to a hot runner nozzle head  32  by bolts  64  (only one being shown). Inside the housing is a displaceable member being a slidable member in the form of a single piston  66   a.  Attached to the piston  66   a  is an axial translation member in the form of a connector pin  69  which is similarly dimensioned, integrally formed and co-axial with a valve pin  53 . The connector pin  69  is slidable in the housing  54   a  coaxially with the first axis  44 . The valve pin  53  has a tip  55  positioned in the end portion  42  and moveable under the influence of the connector pin  69  between a first position in which the tip portion  55  is clear of the outlet  34  and a second position in which the tip portion  55  is blocking the outlet  34  to stop the flow of melt therethrough.  
         [0040]    The housing  54   a  defines a compartment  57   a,  and a pair of fluid inlets  80 ,  82  extend into the compartment  57   a,  one on either side of the piston  66   a.  The piston  66   a  is slidable between the inlets  80 ,  82  and the actuator  52   a  further includes a mechanism (not shown) for supplying pressurized air alternately to the inlets  80 ,  82  to displace the piston  66   a  within the housing  54   a.  When pressurized air is supplied to the inlet  80 , the piston  66   a  moves in a direction designated by arrow  88  and the tip portion  55  of the valve pin  53  is moved into the second position in which it blocks the outlet  34 . Conversely, when pressurized air is supplied to the inlet  82 , the piston  66   a  moves in the direction of arrow  90  and the tip portion  55  moves into the first position in which it is clear of the outlet  34 .  
         [0041]    The actuator is effective in applying a force on the valve pin  53  which is evenly distributed about the first axis  44 . This is achieved by providing a balancing guide pin  122  attached to the piston  66   a  on the same side as the valve pin  53 . As can be seen in the drawing, the housing has a cylindrical wall  56  having an inner cylindrical surface  58  defined about a second axis  124  about which the piston  66   a  is also defined. The guide pin  122  is disposed about a third axis  126  parallel to the first and second axes  44 ,  124 , the first and third axes  44 ,  126  being equidistantly radially spaced from the second axis  124  in opposite directions. The housing  54   a  has a first guide in the form of a cylindrical valve pin guide  74 , attached to an end wall  62  of the housing  54   a  which is configured, positioned and dimensioned to receive and guide the valve pin  53  out of the housing  54   a  along the first axis  44 . The housing  54   a  further includes a second guide  128  which is also attached to the end wall  62  and is positioned, configured and dimensioned to receive and guide the guide pin  122  along the third axis  126 . As the integral valve and connector pins  53 ,  69  are laterally spaced from the axis of the piston  66   a,  such being the second axis  124 , the presence of the guide pin  122  and second guide  128  promotes retention of the lateral orientation of the piston  66   a  as it slides within the housing  54   a.  This, in turn, helps to ensure that a force is applied to the valve pin  53  which is evenly distributed about the first axis  44 .  
         [0042]    The valve pin guide  74  also acts as a seal around the connector portion  69  to prevent excessive leaking of gas from the compartment  57   a.  Although not shown, the hot runner nozzle  22  also has a valve pin bushing seated in an opening leading into the outlet portion  48  and positioned, configured and dimensioned to receive the valve pin  53  and guide it into the end portion  42  along the first axis  44 . The valve pin bushing is dimensioned to act also as a seal to minimize leakage of melt out of the outlet portion  48  of the nozzle body  24 .  
         [0043]    To ensure that melt flowing through the melt channel  36  is maintained between a predetermined desired temperature range, the system  120  also includes a coiled heater  94  embedded in the nozzle body  24 . As in the case of the first embodiment, the heater  94  has one end proximate the inlet  26 , an opposite end proximate the outlet  34  and an intermediate portion surrounding the offset portion  46  coaxially relative to the portion of the melt channel  36  extending through the offset portion  46 .  
         [0044]    Referring now to FIG. 3, a valve-gated injection molding system according to a another embodiment of the invention, designated by reference numeral  220  is shown. Once again, like reference numerals have been used to refer to like parts and only the differences between this embodiment and the first preferred embodiment will be described in detail. The system  220  includes two hot runner nozzles  22   b  connected to a heated manifold  222  in which are embedded manifold heaters  224 . Hot pressurized melt is discharged from a machine nozzle  28  into a sprue bushing  226 . From there, the melt flow through a manifold melt channel  228 , into inlets  26  of the hot runner nozzles  22   b,  through melt channels  36  defined by nozzle bodies  24   b  of the hot runner nozzles  22   b,  and is discharged through outlets  34 . The melt then flows through channels in a mold plate  230  and into mold cavities  40 . Cooling channels  41  are disposed in the mold plate  230  to keep it cool.  
         [0045]    Once again, the outlets  34  are disposed about a first axis  44  and the nozzle bodies  24   b  have end portions  42  located adjacent to the respective outlets  34  and disposed about first axes  44 . The nozzle bodies  24   b  also have offset body portions  46   b  located between the inlets  26  and the end portions  42  and being laterally offset relative to the respective first axes  44 .  
         [0046]    The system  220  further includes an actuator  52   b  external to and positioned laterally from the nozzle bodies  24   b  relative to the first axis  44 . The actuator  52   b  has two closed cylindrical housings  54  and an axial translation member in the form of a connector pin  69  located and slidable in each housing  54  coaxially with the first axes  44 . Integrally connected with the connector pins  69  are respective valve pins  53  also extending along the first axis  44 . The valve pins  53  have respective tip portions  55  positioned in the end portions  42  and moveable under the influence of the connector pins  69  between a first position in which the tip portions  55  are clear of the outlets  34  and a second position in which the tip portions  55  are blocking the outlets  34  to stop the flow of melt therethrough.  
         [0047]    In this embodiment, the housings  54  are mounted to a central mounting member  231  which is coupled to the manifold  222 . Located in each housing  54  is a displaceable member which is a slidable member in the form of a single coaxial with and slidable along the first axis  44 . The pistons  66   b  are displaceable under the influence of pressurized air entering spaces on either side of the pistons through inlets (not shown). A mechanism (also not shown) is operatively coupled to the inlets to supply the inlets with pressurized air in alternating fashion.  
         [0048]    To heat melt flowing through the melt channels  36  a clamp heater  94   b  is mounted to each offset portion  46   b.  The claim heaters  94   b  are coaxial with the portions of the melt channels  36  flowing through the offset portions  46   b  and thereby apply balance heat to that portion.  
         [0049]    It will be appreciated that the system  220  may include additional injection nozzles and a corresponding number of pistons, housings, and valve pins to suit different manifold configurations and other molding parameters. For example, one can use a single manifold and two opposed arrays of nozzle to apply this valve gating arrangement to a stack mold injection molding machine.  
         [0050]    Referring now to FIG. 4, a valve-gated injection molding system according to another embodiment of the invention, designated generally by reference numeral  320 , is shown. Once again, like reference numerals have been used to denote like parts and only differences relative to the earlier described embodiments will be discussed in detail. The system  320  includes a single split nozzle body  24   c  having a single offset portion  46   c  and two end portions  42   c.  Each end portion  42   c  is defined about a first axis  44  along which a respective valve pin  53 , connector pin  69 , and piston  66  extends.  
         [0051]    In this embodiment, the melt channel  36  splits into two channels  232 ,  234 , downstream of the offset portion  46   c,  leading to respective outlets  34 . Thus, this is an example of a system having a single split nozzle body  24   c  defining a split melt channel  36  having a plurality of end portions  42   c  adjacent to a corresponding plurality of outlets  34 , the system also having a corresponding plurality of valve pins  53 , axial translation members in the form of integral connector pins  69 , and housings  54 .  
         [0052]    [0052]FIG. 5 a  depicts a valve-gated injection molding system according to another embodiment of the invention and designated generally by reference numeral  420 . The system  420  includes four nozzle bodies  24   d,  four valve pins  53  and four axial translation members in the form of integral connector pins  69  slidable in a single housing  54  (only two of each being shown). The same design is applicable to two, three or more valve gated outlets. Also shown are electrical wires  422 ,  424  which carry current to and from coiled heaters  94  embedded in the nozzle bodies  24   d,  as is known in the art. The nozzle bodies  24   d  are connected to a manifold  426  which carries melt from a machine nozzle (not shown) to inlets  26  of the nozzle bodies  24   d.  Like the earlier embodiments, the system  420  has a pneumatically-operated actuator which includes two pistons slidable in the housing  54 . The integral connector pins  69  are connected to both pistons for movement therewith in unison along respective first axes  44 . The first axes  44  are equidistantly laterally spaced from a second axis  428  about which the pistons  66 ,  68  and cylindrical wall  56  of the housing  54  are defined. Consequently each connector pin  69  or valve pine  53  serves to balance the other and the actuator is effective in applying forces on the valve pins  53  which are evenly distributed about the first axes  44 .  
         [0053]    In this embodiment, the pistons are moved in the direction of arrow  88  by pressurized air discharged through an inlet  80  extending into the housing  54 . Conversely, pistons  66 ,  68  are moved in the direction of arrow  90  by pressurized air discharged into the housing through an inlet  82 .  
         [0054]    The manifold  426  has four manifold melt channels leading from a central channel  430  to respective inlets  26  of the nozzle bodies  24   d.  This will be more readily understood with reference to FIG. 5 b  which is a schematic illustration of the manifold melt channels  432  from an axial perspective. Thus, the system  420  comprises a plurality of nozzle bodies  24   d  arranged laterally around a single housing  54  and a corresponding plurality of each of the axial translation members (i.e. connector pins  69 ) and the valve pins  53 .  
         [0055]    Referring now to FIG. 6 a,  a valve-gated injection molding system  520  according to another embodiment of the invention is shown. The system  520  is similar in every respect to the system  20  except that it employs a known bladder actuator  52   e  shown in this figure to be in a closed position. The actuator  52   e  has a cylindrical housing  54   e  bolted to the nozzle head  30  laterally from an offset body portion  46  of the nozzle body  24 . The system  520  comprises an elongate valve pin  53  extending along a first axis  44  and having a tip portion  55  positioned in the end portion  42 . The valve pin  53  is operatively coupled to a displaceable member in the form of a flexible bladder  521  located in the housing  54   e  and dividing the housing  54   e  into first and second spaces, the first space being inside the bladder  521 , the second space being outside of the bladder  521 . The actuator  52   e  further includes a pair of first and second inlets  80   e,    82   e,  extending through the housing and communicating with the first and second spaces, respectively, and a mechanism (not shown) operable to alternately supply pressurized fluid in the form of pressurized air to the first and second inlets  80   e,    82   e.  When pressurized air is supplied to the first space, the bladder  521  moves in a first direction, i.e. expands, as shown in this figure. When pressurized air is supplied to the second space, the bladder  521  moves in a second direction, i.e. collapses, as shown in FIG. 6 b.  The valve pin  53  is operatively coupled to the bladder and movable to a first position in which the tip portion  55  is clear of the outlet  34  when the bladder  521  collapses, and to a second position in which the tip portion  55  is blocking the outlet  34  to stop the flow of melt therethrough when the bladder  521  expands.  
         [0056]    Integrally and co-axially formed with the valve pin  53  is a connector pin  69  of the actuator  52   e.  In this embodiment, the actuator  52   e  has a pin attachment  522  is affixed to the connector pin  69  by the use of threads. A lock nut  524  is further threaded on the top of the connector pin  69  to secure the pin attachment  522  to the connector pin  69 . It will be appreciated that the use of threads in the foregoing description is for illustration purposes only. A multitude of attachment means could easily be employed by someone skilled in the art.  
         [0057]    The bladder  521  is fixedly attached to the pin attachment  522  through a wedging action by installation of a top plug  523 . The wedging action between the top plug  523  and the pin attachment  522  is sufficient to provide a reliable seal for containment of pressurized air in the bladder  521 . The bladder  521  is manufactured from flexible material like rubber including fiber reinforced rubber.  
         [0058]    The actuator  52   e  further comprises a fixed inner cylinder  530  which interfaces with a bottom wall of the housing  54   c.  The inner cylinder  530  is located inside the bladder  521  and surrounds the connector pin  69  thereby providing an annular conduit for the transmission of pressurized air to the inside of the bladder  521 . A bottom area of the bladder  521  is fixedly attached to the inner cylinder  30  also by a wedging action through the installation of a bottom plug  528 . The wedging action between the inner cylinder  530  and the bottom plug  528  is sufficient to provide a reliable seal for the containment of pressurized air inside the bladder  521 .  
         [0059]    The inner cylinder  530  further comprises at least one hole that aligns with the inlets  80   e  for the communication of pressurized air to the inside of the bladder  521 . In this embodiment the inner cylinder has a plurality of holes along the wall of the inner cylinder  530  which allow the communication of pressurized air to expand the walls of the bladder  521  thereby reducing the overall length of the bladder  521 .  
         [0060]    As the walls of the bladder  521  expand, and the overall length of the bladder  521  is reduced, the pin attachment  522  moves downwardly along an inner cylindrical surface of a cylindrical wall  56  of the housing  54   e.  This motion in turn moves the position of the valve pin  53  to the second position thereby blocking the outlet  34  and stopping the flow of melt therethrough.  
         [0061]    When the bladder  521  is fully expanded, the top surface of the inner cylinder  530  contacts a bottom surface of the pin attachment  522  thereby preventing continued motion. A top seal  532  and a bottom seal  534  are provided to prevent the leakage of the pressurized air. These seals are high temperature resistant O-rings; however, other suitable seals may be used as are known in the art.  
         [0062]    Referring to FIG. 6 b,  the bladder is collapsed by supplying pressurized air to the inlets  82   e  (as shown by arrows B′). As the bladder  521  is collapsed, any pressurized air inside the bladder  521  escapes as shown by arrows A, and the length of the bladder  521  increases. As the bladder  521  lengthens, it retracts the connector pin  69  integrally formed with the valve pin  53 , thereby moving the tip portion  55  of the valve pin  53  clear of the outlet  34 .  
         [0063]    [0063]FIG. 6 c  is an enlarged view of the area designated by reference numeral  6   c  in FIG. 6 b  and shows an alternative means for retracting the connector pin  69  and hence valve pin  53 . Instead of supplying pressurized gas to the inlet  82   e,  a spring  566  may be axially located between and contacting the pin attachment  522  and the inner cylinder  530  thereby applying a force on the pin attachment  522  to move it upwardly thereby collapsing the bladder  521 . As a further alternative, conditions may exist where one could rely on the resiliency of the bladder  521  itself to return to a collapsed state thereby moving the tip portion  55  of the valve pin  53  clear of the outlet  34 .  
         [0064]    [0064]FIG. 7 shows a valve-actuated injection molding system  620  according to a further aspect of the invention. This system is used for edge or side injection molding applications, where the mold gate  34  is located on any side of the cavity. The system  620  is similar in every respect to the system  20  except that it includes an end portion  42   f  located adjacent to an outlet  34  which end portion  42   f  and outlet  34  are not defined about a first axis  44  about which a valve pin  53  and integral connector pin  69  extend. In this embodiment, the end portion  42   f  and outlet  34  are disposed transversely to the first axis  44  and the outlet  34  leads into a mold cavity  40   f  disposed laterally from the first axis  44  rather than axially as in the case of the earlier embodiments. Thus, the valve pin  53  has a tip portion  55  positioned in the end portion and is movable under the influence of the axial translation member (i.e. connector pin  69 ) between a first position in which the tip portion is clear of the melt channel  36  and a second position in which it is blocking the melt channel to stop the flow of melt through the outlet.  
         [0065]    Numerous alternatives to the above described embodiments will become apparent to the person skilled in the art. For example, the actuators may be fluid operated including using different gases and liquids such as oil. Furthermore, a solenoid arrangement may be used instead of a pneumatic piston arrangement, such as that described in U.S. Pat. No. 5,288,225.  
         [0066]    It will further be appreciated that the invention provides valve-gated injection molding system which may be mounted to a manifold or directly to a machine nozzle. Also, while particularly useful in connection with in-line systems, the invention is not to be limited to such systems and may be for single cavity, multi-cavity and stack mold applications.  
         [0067]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that the invention is defined by the claims that follow.