specific embodiments of the present invention are now described with reference to the figures , where like reference numbers indicate identical or functionally similar elements . referring now to fig1 , a first embodiment of the invention is described . an injection molding system 100 includes a manifold 102 and a plurality of nozzles , such as nozzle 104 . nozzle 104 is a valve - gated hot runner nozzle , with a heater 127 and a thermocouple 128 . a manifold melt channel 106 is disposed within manifold 102 and conveys melt to a plurality of nozzle channels , such as for example nozzle melt channel 107 , which further conveys the melt through a gate 108 into mold cavity 109 . in this embodiment , there are several mold cavities , such as for example mold cavity 109 , of equal or almost equal size and shape in communication with several nozzles ( not shown ), such as nozzle 104 . each cavity has a single mold gate 108 . the present invention allows multiple cavities of equal size to be filled in the same cycle or time period by “ balancing ” the melt flow through manifold 102 , as will be explained in further detail below . as gate 108 is a valve gate , the front portion of a valve pin 110 is disposed within nozzle melt channel 107 . valve pin 110 extends through a portion of manifold melt channel 106 to a valve pin actuation mechanism 112 , which is disposed longitudinally above manifold 102 . gate 108 allows the flow of melt into mold cavity 109 . in a first position , valve pin 110 is retracted from gate 108 by operation of valve pin actuation mechanism 112 to allow melt to flow through gate 108 into mold cavity 109 . in a second position , shown in fig3 and 4 , valve pin 110 is seated within gate 108 by operation of valve pin actuation mechanism 112 to prevent the flow of melt into mold cavity 109 . valve pin actuation mechanism 112 includes a piston 113 driven by any of the various actuation driving mechanisms known in the art , including but not limited to pneumatic , hydraulic , or cam and lever devices . a pneumatic driving system operates by linking an external air source to the piston driving mechanism with valves controlled by a timing circuit which applies and releases the pressure in a repetitive timed sequence in conjunction with the application of pressure to the melt from the molding system . a hydraulic driving system operates in the same manner as the pneumatic system , only hydraulic fluid is substituted for air . in an alternate embodiment , a bladder piston , as shown and described in the co - pending u . s . appl . no . 60 / 363 , 891 filed on mar . 14 , 2002 by the same assignee which is incorporated herein in its entirety by reference thereto , may be used . a bladder piston is an expandable and elongated bag which shortens in length when filled with a pressurized fluid like air , water , or oil . one end of the bladder is affixed to a valve pin such that , as the bladder is pressurized , it contracts in length and the valve pin is unseated from the mold gate orifice , which allows the melt to flow into the mold cavity . similarly , depressurizing the bladder causes the bladder to increase in length , which seats the valve pin in the mold gate orifice and stops the flow of the melt into the mold cavity . valve pin actuation mechanism 112 can be controlled in a variety of ways . preferably , one or more pressure transducers 125 are linked to servo valve 123 . servo valve 123 is linked to the driving mechanism ( not shown ). when the pressure inside the system , as measured by pressure transducers 125 , reaches a first level , servo valve 123 switches so that fluid or air from the driving mechanism can flow to valve pin actuation mechanism 112 , causing piston 113 to move valve pin 110 within gate 108 . when pressure in the system is measured by pressure transducers 125 to be a second level , servo valve 123 switches so that fluid or air from the driving mechanism is shut off , causing piston 113 to retract valve pin 110 from gate 108 . alternatively , valve pin actuation mechanism 112 may be controlled by mechanisms other than servo valve 123 . for example , in one embodiment , valve pin actuation mechanism 112 may be controlled by a computer that follows a pre - determined cycle . the computer signals circuitry connected to the driving mechanism according to the cycle , and the circuitry then triggers the driving mechanism , and piston 113 is driven up or down . accordingly , rather than controlling valve pin 110 by servo valve 123 movement based on pressure readings , the computer controlled arrangement is based on the timing of each cycle . disposed within nozzle melt channel 107 is a flow control pin 114 . as with valve pin 110 , flow control pin 114 extends through a portion of manifold melt channel 106 to a flow control pin actuation mechanism 117 . flow control pin actuation mechanism 117 is located between manifold 102 and valve pin actuation mechanism 112 , although the relative position of actuation mechanisms 112 , 117 could easily be reversed . flow control pin 114 is in one embodiment a sleeve which coaxially surrounds valve pin 110 , as shown in fig1 , although pins 110 and 114 could also simply run parallel to one another within a larger diameter nozzle melt channel 107 . flow control pin 114 enables control of the amount of melt passing through nozzle 104 independent of the functioning of valve pin 110 . to achieve this purpose , flow control pin 114 includes a flow control surface 116 , a head disposed at the terminal end of flow control pin 114 within nozzle 104 . in the embodiment of fig1 , flow control surface 116 has a larger diameter than that of the shaft of flow control pin 114 , and the distal end of flow control surface 116 has a tapered geometry . nozzle melt channel 107 has a complementary geometry at a flow control surface 120 . in a first position , shown in fig1 and 2 , flow control surface 116 is positioned at or near flow control surface 120 . due to the complementary geometry of surface 116 and nozzle melt channel 107 at surface 120 , surface 116 constricts the flow of melt through nozzle melt channel 107 to decrease the volume of melt thereby decreasing the flow of material to gate 108 . in a second position , shown in fig3 and 4 , flow control surface 116 is positioned away from flow control surface 120 so that the flow of melt through nozzle melt channel 107 is not constricted . intermediate positioning of flow control surface 116 , where the flow of melt through nozzle melt channel 107 is only partly constricted , is also possible . flow control pin actuation mechanism 117 , like valve pin actuation mechanism 112 , is a piston 118 driven by any of the actuation driving mechanisms known in the art , such as pneumatic , hydraulic , cam and lever devices , or bladder pistons . flow control actuation mechanism 117 is controlled as described above with respect to valve pin actuation mechanism 112 . flow control actuation mechanism 117 can be controlled in a variety of ways . preferably , one or more pressure transducers 124 are linked to servo valve 122 . servo valve 122 is linked to the driving mechanism ( not shown ). when the pressure inside the system , as measured by pressure transducers 124 , reaches a first level , servo valve 122 switches so that fluid or air from the driving mechanism can flow to flow control actuation mechanism 117 , causing piston 118 to move flow control pin 110 towards flow control surface 120 . when pressure in the system is measured by pressure transducers 124 to be a second level , servo valve 122 switches so that fluid or air from the driving mechanism is shut off , causing piston 118 to retract flow control pin 114 away from flow control surface 120 . alternatively , flow control actuation mechanism 117 may be controlled by mechanisms other than servo valve 122 . for example , in one embodiment , flow control actuation mechanism 117 may be controlled by a computer that follows a pre - determined cycle . the computer signals circuitry connected to the driving mechanism according to the cycle , and the circuitry then triggers the driving mechanism , and piston 118 is driven up or down . accordingly , rather than controlling flow control pin 114 by servo valve 122 movement based on pressure readings , the computer controlled arrangement is based on the timing of each cycle . in addition to pressure information controlling flow control pin 114 , in another embodiment of the present invention temperature information may also be used to control flow control pin 114 and therefore adjust the position of flow control pin 114 . further , in addition to thermocouple 128 , injection molding system 100 may include additional temperature sensors ( not shown ) to help control of melt flow . the geometry of nozzle melt channel 107 is shown in fig1 and 2 to have a slightly larger diameter in the region of flow control surface 116 , i . e ., the nozzle melt channel expands and then tapers back to the original diameter at a lower end of flow control surface 120 . this geometry allows flow control surface 116 , which has a larger diameter than the rest of flow control pin 114 , to move freely within nozzle melt channel 107 . however , many different geometries are contemplated by the present invention . for example , the nozzle melt channel 107 may have a first diameter which is greater than the diameter of the flow control surface 116 which tapers at flow control surface 120 to a second diameter . referring now to fig5 – 6 , a second embodiment of the present invention is shown . injection molding system 500 includes a manifold 502 and a nozzle 504 . nozzle 504 is a valve - gated hot runner nozzle . injection molding system 500 further includes a thermocouple 528 . a manifold melt channel 506 is disposed within manifold 502 and conveys melt to a nozzle melt channel 507 , which further conveys the melt through gate 508 into mold cavity 509 . the shaft of a valve pin 510 extends through a portion of manifold melt channel 506 to a valve pin actuation mechanism ( not shown ), which is disposed longitudinally above manifold 502 . gate 508 controls the flow of melt into mold cavity 509 . in a first position , valve pin 510 is unseated from gate 508 by operation of the valve pin actuation mechanism to allow melt to flow through gate 508 into mold cavity 509 . in a second position , shown in fig6 , valve pin 510 is seated within gate 508 by operation of the valve pin actuation mechanism to prevent the flow of melt into mold cavity 509 . the actuation of valve pin 510 and the functioning , variations , and control of the valve pin actuation mechanism may be any of the systems as described above with respect to the first embodiment , for example utilizing a transducer 524 and a servo valve 523 . disposed within manifold melt channel 506 is a flow control pin 514 . the shaft of flow control pin 514 extends through a portion of manifold melt channel 506 to a flow control pin actuation mechanism 517 . flow control actuation mechanism 517 is located between manifold 102 and the valve pin actuation mechanism ( not shown ), although their relative positions could easily be reversed . flow control pin 514 enables control of the flow of melt passing through nozzle 504 independent of the functioning of valve pin 510 . to achieve this purpose , flow control pin 514 includes a flow control surface 516 , a head disposed at the terminal end of flow control pin 514 within manifold 502 . flow control surface 516 has a larger diameter than that of the shaft of flow control pin 514 , and the distal end of flow control surface 516 has a tapered geometry . manifold melt channel 507 has a complementary geometry at a flow control surface 520 . in a first position , shown in fig5 , flow control surface 516 is positioned at or near flow control surface 520 . due to the complementary geometry of surface 516 and manifold melt channel 506 at surface 520 , surface 516 constricts the flow of melt through manifold melt channel 507 . in a second position , shown in fig6 , flow control surface 516 is positioned away from flow control surface 520 so that the flow of melt through manifold melt channel 506 is not constricted . intermediate positioning of flow control surface 516 , where the flow of melt through manifold melt channel 506 is only partially constricted , is also possible . as shown in fig5 , manifold melt channel 506 leads away from flow control surface 520 at an angle . this offset configuration allows for an optional second manifold melt channel 506 a to be added to the system so that a second nozzle ( 504 ) may be flow controlled simultaneously with nozzle 504 . however , the present invention is not limited to this geometry , and nozzle melt channel 507 may be disposed in a collinear arrangement with manifold melt channel 506 . with this arrangement , flow control pin 514 would have the sleeve - like configuration as described above with respect to the first embodiment . as described above with respect to the first embodiment , flow control pin actuation mechanism 517 , is a piston 518 driven by any of the actuation driving mechanisms known in the art , such as pneumatic , hydraulic , cam and lever devices , or bladder pistons . flow control actuation mechanism 517 is controlled as described above with respect to the first embodiment . fig7 and 8 show another embodiment of the present invention , depicting another possible arrangement of a valve pin 710 and an independently actuated flow control pin 714 within an injection molding system 700 . in this embodiment , valve pin 710 is laterally offset with respect to actuated flow control pin 714 and at an angle α therewith . fig7 shows valve pin 710 in a first position , unseated from gate 708 to allow melt to flow through gate 708 into mold cavity 709 . fig8 shows valve pin 710 seated within gate 708 to prevent the flow of melt into mold cavity 709 . system 700 functions similarly as described above with respect to the first and second embodiments , for example utilizing transducers 724 and 725 , a servo valve 722 , and a thermocouple 728 . fig9 and 10 show another embodiment of the present invention , depicting another possible arrangement of a valve pin 910 and an independently actuated flow control pin 914 within an injection molding system 900 . valve pin 910 and independently actuated flow control pin 914 are positioned in the same configuration as shown in fig1 , except that the servo valve ( 922 ) for controlling valve pin 910 has been eliminated . fig9 shows valve pin 910 in a first position , unseated from gate 908 by operation of valve pin actuation mechanism 912 to allow melt to flow through gate 908 into mold cavity 909 . fig1 shows valve pin 910 seated within gate 908 by operation of valve pin actuation mechanism 912 to prevent the flow of melt into mold cavity 909 . system 900 functions similarly as described above with respect to the first and second embodiments , for example utilizing a transducer 924 , a servo valve 922 , and a thermocouple 928 , except that valve pin actuation mechanism 912 is controlled by a method other than a servo valve . as previously mentioned , valve pin actuation mechanism 912 may be controlled by a computer that follows a pre - determined cycle . the computer would signal circuitry connected to the driving mechanism according to the cycle , and the circuitry would trigger the driving mechanism , and piston 913 would be driven up or down . alternatively , valve pin actuation mechanism 912 may be controlled by an operator who manually triggers the driving mechanism . fig1 a and 11b show an application of the present invention wherein multiple nozzles 1104 a and 1104 b are feeding one large mold cavity 1109 . valve pins 1110 a and 1110 b and independently actuated flow control pins 1114 a and 1114 b are positioned in the same configuration as shown in fig1 , and function similarly as described above with respect to the first and second embodiments . in this embodiment of the present invention , the positions of valve pins 1110 a and 1110 b and flow control pins 1114 a and 1114 b are controlled in such as manner to produce an acceptable knit line where the melt from each nozzle 1104 a and 1104 b meets within mold cavity 1109 . fig1 a shows valve pin 1110 a unseated from gate 1108 a to allow melt to flow through gate 1108 a into mold cavity 1109 , while valve pin 1110 b is seated within gate 1108 b to prevent flow of melt into mold cavity 1109 . in fig1 b , valve pin 1110 a is seated within gate 1108 a to prevent the flow of melt into mold cavity 1109 , while valve pin 1110 b is unseated from gate 1108 b to allow melt to flow through gate 1108 b into mold cavity 1109 . it would be understood to one of ordinary skill in the art that each valve pin and flow control pin are independently actuated to controllably regulate the flow of the melt to achieve optimal molding conditions within the mold cavity and thereby produce an improved molded part . fig1 a and 12b show another application of the present invention wherein a first nozzle 1204 a is feeding a first mold cavity 1209 a and a second nozzle 1204 b is simultaneously feeding a second cavity 1209 b of a different size than first cavity 1209 a . valve pins 1210 a and 1210 b and independently actuated flow control pins 1214 a and 1214 b are positioned in the same configuration as shown in fig1 , and function similarly as described above with respect to the first and second embodiments . multiple cavities of different sizes may be filled in the same cycle or time period due to the flow control provided by valve pins 1210 a and 1210 b and flow control pins 1214 a and 1214 b . each of the valve and flow control pins are independently actuatable to provide balancing of the melt flow from manifold 102 through each respective nozzle and into the respective mold cavities . fig1 a shows valve pin 1210 a unseated from gate 1208 a to allow melt to flow through gate 1208 a into first cavity 1209 a , while valve pin 1210 b is seated within gate 1208 b to prevent flow of melt into second cavity 1209 b . in fig1 b , valve pin 1210 a is seated within gate 1208 a to prevent the flow of melt into first cavity 1209 a , while valve pin 1210 b is unseated from gate 1208 b to allow melt to flow through gate 1208 b into second cavity 1209 b . while in fig1 a , 11 b , 12 a , and 12 b , one valve pin is shown seated and the other valve pin is shown unseated , it should be understood that both valve pins may simultaneously be seated or unseated dependent on the molding conditions , and that each valve pin is actuatable to control flow of melt from the nozzle channel to the mold cavity at various intermediate positions . while various embodiments of the present invention have been described above , it should be understood that they have been presented by way of example only , and not limitation . it will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention . thus , the breadth and scope of the present invention should not be limited by any of the above - described exemplary embodiments , but should be defined only in accordance with the following claims and their equivalents .