Abstract:
An injection molding apparatus comprising: an injection molding machine, a heated manifold, a nozzle, the downstream end of the nozzle comprising an inner tubular member having a central flow channel and an outer circumferential surface and an outer tubular member having an inner tubular surface, the outer tubular member forming a seal surrounding the gate, the inner and outer tubular members being adapted to form a sealed circumferential gap, the inner tubular member including one or apertures extending radially through the inner tubular member to route flow radially from the fluid flow channel into the circumferential gap.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims the benefit of priority to PCT/US16/022452 filed Mar. 15, 2016 which claims the benefit of priority to U.S. Provisional Application Ser. No. 62/133,589 filed Mar. 16, 2015, the disclosures of both of which are incorporated by reference in their entirety as if fully set forth herein. 
         [0002]    This application is a continuation of and claims the benefit of priority to International application serial no. PCT/US14/31000 filed Mar. 18, 2014 and is a continuation of and claims the benefit of priority to International application serial no. PCT/US14/52639 filed Aug. 26, 2014. 
         [0003]    The disclosures of all of the following are incorporated by reference in their entirety as if fully set forth herein: U.S. Pat. No. 5,894,025, U.S. Pat. No. 6,062,840, U.S. Pat. No. 6,294,122, U.S. Pat. No. 6,309,208, U.S. Pat. No. 6,287,107, U.S. Pat. No. 6,343,921, U.S. Pat. No. 6,343,922, U.S. Pat. No. 6,254,377, U.S. Pat. No. 6,261,075, U.S. Pat. No. 6,361,300 (7006), U.S. Pat. No. 6,419,870, U.S. Pat. No. 6,464,909 (7031), U.S. Pat. No. 6,599,116, U.S. Pat. No. 7,234,929 (7075US1), U.S. Pat. No. 7,419,625 (7075US2), U.S. Pat. No. 7,569,169 (7075US3), U.S. patent application Ser. No. 10/214,118, filed Aug. 8, 2002 (7006), U.S. Pat. No. 7,029,268 (7077US1), U.S. Pat. No. 7,270,537 (7077US2), U.S. Pat. No. 7,597,828 (7077US3), U.S. patent application Ser. No. 09/699,856 filed Oct. 30, 2000 (7056), U.S. patent application Ser. No. 10/269,927 filed Oct. 11, 2002 (7031), U.S. application Ser. No. 09/503,832 filed Feb. 15, 2000 (7053), U.S. application Ser. No. 09/656,846 filed Sep. 7, 2000 (7060), U.S. application Ser. No. 10/006,504 filed Dec. 3, 2001, (7068), U.S. application Ser. No. 10/101,278 filed Mar. 19, 2002 (7070) and international applications PCT/US2011/062099 and PCT/US2011/062096 and PCT/US2015/10270 
     
    
     BACKGROUND OF THE INVENTION 
       [0004]    Injection molding systems having nozzle inserts and configurations that form circumferential gaps and pockets with the flow channel of the nozzle have been used in systems such as shown in PCT/US15/10270. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the invention there is provided an injection molding apparatus comprising: 
         [0006]    an injection molding machine  20 , 
         [0007]    a heated manifold  30  that receives an injection fluid material  23  from the injection molding machine  20 , 
         [0008]    a nozzle  50  having a fluid flow channel  300  having a longitudinal axis A and an upstream end  50   u  that receives the injection fluid material  23  from the heated manifold  30  and delivers the injection fluid to a downstream end  50   d  that sealably delivers the injection fluid  23  to a gate  85  of a cavity  80  of a mold body  88 , 
         [0009]    the downstream end  50   d  of the nozzle  50  comprising an inner tubular member  55  having an outer circumferential surface  55   es  and an outer tubular member  56  having an inner tubular surface  56   is , the outer tubular member  56  forming a seal  57 ,  86 ,  54 ,  58  surrounding the gate  85 , 
         [0010]    the inner  55  and outer  56  tubular members being adapted to form a sealed circumferential gap G between the outer circumferential surface  55   es  of the inner tubular member  55  and the inner circumferential surface  56   is  of the outer tubular member  56 , the circumferential gap G circumferentially surrounding the fluid flow channel  300 , 
         [0011]    the inner tubular member  55  including one or apertures  500  extending radially R through the inner tubular member  55  between the fluid flow channel  300  and the circumferential gap G to enable flow of injection fluid  23  that is injected in an upstream to downstream path of flow through the fluid flow channel  300  to flow radially R from the fluid flow channel  300  into the circumferential gap G. The circumferential gap G is preferably adapted to route the flow of injection fluid downstream to the mold cavity  80 . 
         [0012]    The circumferential gap G and the fluid flow channel  300  are preferably adapted to communicate with each other downstream to form a common stream of flow  23   c  and route the injection fluid material  23  to the gate  85 . 
         [0013]    The one or more apertures  500  are preferably configured to direct or route injection fluid  23  that is injected from the upstream end of the nozzle downstream through the fluid flow channel  300  and radially R and longitudinally A through the circumferential gap G. 
         [0014]    The apparatus typically further comprises a controller  16  having a program that contains instructions that control axial positioning of an outer surface  90   tcs ,  90   mds  of the valve pin  90  relative to an inner surface  55   is  of the inner tubular member  55  to form a flow restriction UG through the nozzle channel  300  for one or more predetermined amounts of time during the course of an injection cycle sufficient to cause flow of fluid material  23  to be routed through an aperture  500  at an elevated rate of flow (GF) through the purge apertures ( 500 ) and the gap (G). 
         [0015]    The one or more apertures  500  typically have a flow axis AA that is configured and disposed at an acute angle X to the longitudinal axis A of the fluid flow channel  300  of the nozzle  50  that is adapted to route the injection fluid  23  radially R in a downstream axial A direction through the gap G toward the gate  85 . 
         [0016]    The inner tubular member  55  is preferably mounted within and circumferentially surrounded by the outer tubular member  56  at the distal end of the nozzle  50   d , the inner tubular member having an outer circumferential mating surface  54  that is sealably engaged against an inner seal surface  58  of the outer tubular member  56  to seal against upstream flow of the injection fluid material  23  through the gap G. 
         [0017]    The outer tubular member  56  preferably has an exterior seal surface  57  sealably engaged against a mold body seal surface  86  to seal against upstream flow the injection fluid material through the gap G. 
         [0018]    The inner tubular member  55  preferably mounted and nested within the outer tubular member  56  in an arrangement that seals injection fluid material against upstream flow through the gap G. 
         [0019]    The apparatus can further comprise a controller  16  containing instructions that direct withdrawal of the valve pin  90  upstream from a gate closed position at one or more reduced rates of travel relative to a maximum rate of travel upstream to one or more partially gate open positions. 
         [0020]    And the controller  16  can contain instructions that direct withdrawal of the valve pin  90  from a gate closed position upstream to one or more partially gate open positions that restrict fluid material  23  flow to a rate less than a maximum rate for one or more predetermined periods of time and subsequently upstream to a fully gate open position. 
         [0021]    In another aspect of the invention there is provided a method of purging the injection nozzle of an apparatus as described above comprising: 
         [0022]    injecting a first injection fluid material through the nozzle of the apparatus, 
         [0023]    injecting a second injection fluid material through the nozzle of the apparatus. 
         [0024]    In another aspect of the invention there is provided a method of purging an injection nozzle employing an injection molding apparatus ( 10 ) comprised of an injection molding machine ( 20 ), a heated manifold ( 30 ) that receives an injection fluid material ( 23 ) from the injection molding machine ( 20 ), a nozzle ( 50 ) having a fluid flow channel ( 300 ) having a longitudinal axis A and an upstream end ( 50   u ) that receives the injection fluid material ( 23 ) from the heated manifold ( 30 ) and delivers the injection fluid to a downstream end ( 50   d ) that sealably delivers the injection fluid ( 23 ) to a gate ( 85 ) of a cavity ( 80 ) of a mold body ( 88 ), wherein the downstream end ( 50   d ) of the nozzle ( 50 ) comprises an inner tubular member ( 55 ) having an outer circumferential surface ( 55   es ) and an outer tubular member ( 56 ) having an inner tubular surface ( 56   is ), the outer tubular member ( 56 ) forming a seal ( 57 ,  86 ,  54 ,  58 ) surrounding the gate ( 85 ), 
         [0025]    wherein the inner ( 55 ) and outer ( 56 ) tubular members are adapted to form a sealed circumferential gap (G) between the outer circumferential surface ( 55   es ) of the inner tubular member ( 55 ) and the inner circumferential surface ( 56   is ) of the outer tubular member ( 56 ), the circumferential gap (G) circumferentially surrounding the fluid flow channel ( 300 ), 
         [0026]    wherein the inner tubular member ( 55 ) is adapted to include one or more apertures ( 500 ) extending radially (R) through the inner tubular member ( 55 ) between the fluid flow channel ( 300 ) and the circumferential gap (G) to enable flow of injection fluid ( 23 ) that is injected in an upstream to downstream direction or path of flow through the fluid flow channel ( 300 ) to flow radially (R) from the fluid flow channel ( 300 ) into the circumferential gap (G), 
         [0027]    wherein the circumferential gap (G) and the fluid flow channel ( 300 ) are adapted to communicate with each other downstream to form a common stream of flow ( 23   c ) of injection fluid material ( 23 ) that is routed to the gate ( 85 ), 
         [0028]    the method comprising: 
         [0029]    controlling axial positioning of an outer surface ( 90   tcs ,  90   mds ) of the valve pin ( 90 ) relative to an inner surface ( 55   is ) of the inner tubular member ( 55 ) during the course of an injection cycle to form a flow restriction (UG) through the nozzle channel ( 300 ) for one or more predetermined amounts of time during the injection cycle sufficient to cause flow of fluid material ( 23 ) to be routed through an aperture ( 500 ) at an elevated rate of flow (GF) through the purge apertures ( 500 ) and the gap (G). 
         [0030]    In another aspect of the invention there is provided a part or product formed by carrying out an injection cycle according to the methods described above. 
         [0031]    In another aspect of the invention there is provided in an injection molding apparatus comprised of an injection molding machine  20  that injects an injection fluid material  23  into a heated manifold  30 , 
         [0032]    a nozzle having a fluid flow channel  300  having a longitudinal axis A and an upstream end  56   u  that receives the injection fluid material  23  from the heated manifold  30  and delivers the injection fluid to a downstream end  50   d  that sealably delivers the injection fluid  23  to a gate  85  of a cavity  80  of a mold body  88 , 
         [0033]    the downstream end  50   d  of the nozzle  50  comprising an inner tubular member  55  having an outer circumferential surface  55 ES and an outer tubular member  56  having an inner tubular surface  56 IS, the outer tubular member  56  sealably surrounding  57 ,  86 ,  54 ,  58  the gate  85 , 
         [0000]    the inner  55  and outer  56  tubular members being arranged relative to each other such that a circumferential gap G is formed between the outer circumferential surface  55 ES of the inner tubular member  55  and the inner circumferential surface  56 IS of the outer tubular member  56 , the circumferential gap G circumferentially surrounding the fluid flow channel  300 , 
         [0034]    the inner tubular member  55  having one or apertures  500  extending radially R through the inner tubular member  55  between the fluid flow channel  300  and the circumferential gap G to enable flow of injection fluid  23  that is injected upstream to downstream through the fluid flow channel  300  to flow radially R from the fluid flow channel  300  into the circumferential gap G. The circumferential gap G is preferably adapted to route the flow of injection fluid downstream to the mold cavity  80 . 
         [0035]    The circumferential gap G and the fluid flow channel  300  are preferably adapted to communicate with each other downstream to form a common stream of flow  23   c  and route the injection fluid material  23  to the gate  85 . 
         [0036]    Preferably the one or more apertures  500  are configured to direct or route injection fluid  23  that is injected from the upstream end of the nozzle downstream through the fluid flow channel  300  and radially R and longitudinally A through the circumferential gap G 
         [0037]    The one or more apertures  500  typically have a flow axis AA that is configured and disposed at an acute angle X to the longitudinal axis A of the fluid flow channel  300  of the nozzle  50  that is adapted to route the fluid material  23  radially R in a downstream axial A direction through the gap G toward the gate  85 . 
         [0038]    The apparatus typically further comprises a controller  16  having a program that contains instructions that control axial positioning of an outer surface  90   tcs ,  90   mds  of the valve pin  90  relative to an inner surface  55   is  of the inner tubular member  55  to form a flow restriction UG through the nozzle channel  300  for one or more predetermined amounts of time during the course of an injection cycle sufficient to cause flow of fluid material  23  to be routed through an aperture  500 . 
         [0039]    The inner tubular member  55  is preferably mounted within and circumferentially surrounded by the outer tubular member  56  at the distal end of the nozzle  50   d , the inner tubular member  55  having an outer circumferential mating surface  54  that is sealably engaged against an inner seal surface  58  of the outer tubular member  56  to seal against upstream flow of the injection fluid material  23  through the gap G. 
         [0040]    The outer tubular member  56  typically has an exterior seal surface  57  sealably engaged against a mold body seal surface  86  to seal against upstream flow the injection fluid material through the gap G. 
         [0041]    The inner tubular member  55  is mounted and nested within the outer tubular member  56  in an arrangement that seals injection fluid material against upstream flow through the gap G. 
         [0042]    The apparatus can further comprise a controller  16  containing instructions that direct withdrawal of the valve pin  90  upstream from a gate closed position at one or more reduced rates of travel relative to a maximum rate of travel upstream to one or more partially gate open positions. 
         [0043]    And the controller  16  can contain instructions that direct withdrawal of the valve pin  90  from a gate closed position upstream to one or more partially gate open positions that restrict fluid material  23  flow to a rate less than a maximum rate for one or more predetermined periods of time and subsequently upstream to a fully gate open position. 
         [0044]    In another aspect of the invention there is provided a method of purging the injection nozzle  50  of an apparatus  10  described immediately above comprising: 
         [0045]    injecting a first injection fluid material through the nozzle of the apparatus, 
         [0046]    injecting a second injection fluid material through the nozzle of the apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]    The above and further advantages of the invention may be better understood by referring to the following description in conjunction with the accompanying drawings in which: 
           [0048]      FIG. 1  is a cross-sectional view of an injection molding machine, hotrunner or heated manifold, nozzle and mold body according to one embodiment of the invention. 
           [0049]      FIG. 2  is a schematic cross-sectional view of the distal end of a preferred embodiment of nozzle insert and valve pin. 
           [0050]      FIG. 2A  is a schematic cross-section view of the nozzle insert and valve pin of  FIG. 2  in a fully closed position. 
           [0051]      FIG. 2B  is a schematic cross-sectional view similar to  FIG. 2A  but showing the valve pin in an initially upstream partially open position 
           [0052]      FIG. 2C  is a schematic cross-sectional view similar to  FIG. 2B  but showing the valve pin in a fully open position. 
           [0053]      FIG. 3  is an enlarged detail view of a portion of  FIG. 2B  showing the relative size of the gaps between the valve pin the nozzle insert and the nozzle part and mold body the valve pin is at 3 mm open. 
           [0054]      FIG. 4  is a schematic cross-sectional view of an alternate embodiment where the outer tubular member extends longitudinally toward and into engagement with the mold body. 
           [0055]      FIG. 5  is a schematic cross-sectional view of an alternate embodiment similar to  FIG. 1  but with an elongated insert. 
           [0056]      FIG. 6  is a schematic cross-sectional view of an alternate embodiment of a nozzle which extends longitudinally toward and in engagement with the mold body. 
       
    
    
     DETAILED DESCRIPTION 
       [0057]      FIGS. 1-6  show various embodiments of an apparatus  10  and nozzle  50  according to the invention. The apparatus typically comprises a top clamp plate  13 , an actuator  15  that reciprocally drive an interconnected valve pin  90  in an upstream-downstream path UD between gate open positions such as shown in  FIGS. 1, 2, 2B, 2C  and gate closed positions such as shown in  FIGS. 2A, 5 . The valve pin  90  is preferably arranged such that the valve pin is mounted within a guide aperture  90   a  that extends through a hotrunner or heated manifold  30  and further extends through a fluid material  23  flow channel  30   c  that is disposed within the heated manifold  30 . The nozzle  50  sealably interconnects the manifold flow channel  30   c  with a central nozzle flow channel  300 . The apparatus  10  typically includes a controller  16  that controls the upstream-downstream UD movement of the valve pin  90  during the course of an injection cycle according to a predetermined algorithm or program. 
         [0058]    The injection machine  20  injects fluid material  23  under pressure in a downstream direction D into the fluid distribution channels  30   d  of the heated manifold  30 . The fluid material  23  is routed further downstream through downstream manifold channel  30   c  and further downstream into and through the nozzle channel  300  eventually to and through gate  85  into mold cavity  80 . As described below, some portion of the fluid material  23  travelling downstream through nozzle channel  300  is routed through lateral nozzle apertures  50  and gap G during the course of downstream flow to and through the gate  85 . 
         [0059]    The apparatus  10  includes a mold body  88  having a gate  85  with which the travel or drive axis A of the nozzle  50  is typically coaxially aligned. The distal end  50   d  of the nozzle  55  includes an inner tubular member or insert  55  typically comprised of a highly heat conductive material. The insert  55  is typically mounted and nested within an outer tubular member  56  that radially surrounds the gate  85  and forms a fluid seal via compression between an outer circumferential mating surface  57  that mates with a complementary inner mating surface  86  of the mold body  88  to prevent injection fluid from flowing upstream around the outside surface of the outer tubular body  56 . 
         [0060]    The outer tubular member  56  is mounted against the mold body  88  via the mating surfaces  57 ,  86  and the inner tubular member or insert  55  is mounted and arranged via mating of an outer circumferential surface  54  against an inner mating surface  58  of the outer tubular member such that a gap G is formed between the outer circumferential surface  55   es  of the inner tubular member  55  and the inner surface  56 IS of the outer tubular member. In the embodiments shown in  FIGS. 1-6 , the distal end surface  55   ds  of the inner tubular member  55  is spaced apart from the mold body  88  such that the member  55  does not engage or contact the mold body  88  in a manner that results in heat conductive contact. As shown in  FIGS. 3, 5  the distal end surface  55   ds  is spaced a selected gap distance GT of typically between about 0.04 mm and about 0.1 mm from the upstream facing surface  88   us  of the mold body. The gap G that is disposed between the outer surface  55   es  and the inner surface  56   is  communicates with the gap G disposed between the distal tip end surface  55   ds  and the mold surface  88   us  such that injection fluid  23  that flows downstream through the nozzle channel  300  to the gate  85  during any given injection cycle can seep through the distal-most portion of the gap G upstream into the larger portion of the gap G that is disposed between the outer surface  55   es  and the inner surface  56   is.    
         [0061]    Residual injection fluid  23  that has seeped into gap G can be flushed or purged out of the gap G by running one or more additional or subsequent purge injection cycles that are separate from normal operational injection cycles. On running such additional or subsequent cycles the injection fluid will travel though apertures  500  along both a lateral or radial R and along a longitudinal A direction on account of the configuration of the apertures  500  having both a lateral R and longitudinal profile with an axis AA that is disposed at an acute angle X to the longitudinal axis A of the nozzle channel  300  that is adapted to route the injection fluid radially R and in a downstream axial A direction through the gap G toward the gate  85 . 
         [0062]    In one embodiment of the invention, the valve pin  90  can be controllably withdrawn upstream beginning from a gate closed position to a position of upstream travel UT such as shown in  FIGS. 2B, 3  where the outside surface of the pin  90  restricts UG flow of injection fluid through the main nozzle channel  300  but better enables a higher volume and rate of injection flow through the purge apertures  500 . When the pin  90  is disposed in such a position such as in  FIGS. 2B, 3  where the pin forms a restriction gap UG (typically between about 0.05 and about 0.5 mm) fluid flow RR longitudinally through the interior of the channel  300  is restricted to a rate that is substantially less than the unrestricted flow rate, velocity or volume that would normally occur under full system pressure when the pin  90  is not restricting flow through channel  300 . The injection fluid  23  that is injected into the channel  300  is still injected under the same pressure and although flow is restricted longitudinally RR through the channel  300 , flow of fluid GF is diverted radially R under a higher rate through purge apertures  500  and downstream GF through gap G. Thus when running a purge cycle of injection fluid subsequent to a prior cycle, the valve pin  90  is preferably withdrawn from a fully gate closed position upstream at a rate of upstream travel that disposes the selectively formed distal portion  90   p  of the pin  90  at an upstream position of travel UT for a preselected period of time that causes the flow of injection fluid to be restricted through channel  300  and to be diverted radially R at an elevated rate of flow GF through the purge apertures  500  and the gap G. 
         [0063]    In the gate closed position shown in  FIGS. 2A, 5 , the outer surface  90   tcs  of the pin  90  engages with the inner surface  88   is  of the gate area to completely surround and seal the gate such that flow R, RR of injection fluid is completely stopped. The pin  90  can be controllably withdrawn upstream beginning from the gate closed position as shown in  FIGS. 2B, 3  to any selected one or more axial upstream-downstream positions UT at which the interior surface  88   is  of the gate forms a flow restriction gap downstream at the gate between the surface  88   is  and the outer surface  90   tcs  of the pin  90 . 
         [0064]    Similarly the pin  90  can be controllably withdrawn upstream beginning from a position as shown in  FIGS. 2B, 3  to any selected one or more axial upstream-downstream positions UT at which the interior surface  55   is ,  55   ms  of the inner tubular member  55  and the complementary outer circumferential surface  90   tcs  form an upstream restriction gap UG for any desired period of time. 
         [0065]    In one embodiment, the pin  90  can be withdrawn and held stationary at one or more axial positions UT along the axial A up and down UD course of travel of the pin  90  such that the pin  90  is disposed in one or more upstream restriction positions UG for some selected period of time such as from about 0.1 to about 10 seconds depending on the normal length of the injection cycle. 
         [0066]    In one embodiment the valve pin  90  can be provided with a maximum downstream diameter section  90   s  that has an outer circumferential surface  90   mds  that is complementary to and mates with a complementary interior mating surface  55   ms  of the inner member  55  such that fluid material  23  flow through channel  300  is stopped or substantially reduced when the surfaces are axially aligned along axis UTM thus forcing downstream flow D of fluid material  23  to flow through apertures  500  and gap G thus flushing out gap G. Such a flushing is typically carried out at the beginning or at the end of an injection cycle via running a separate flush cycle, or can be carried out during the course of an injection cycle for a selected period of time. Alternatively, the diameter of the maximum diameter surface  90   mds  can be selected to be less than the diameter of the complementary surface  55   ms  such that the two surfaces do not mate, but rather are closely similar in size such that a restriction flow gap UG is formed of such a size that downstream flow through the gap UG is substantially restricted when the surfaces are axially aligned along axis UTM or approach becoming axially aligned along axis UTM. 
         [0067]    As the valve pin  90  is driven either downstream or upstream to a position where the maximum diameter surface  90   mds  is approaching axial alignment with the complementary surface  55   ms , the flow restriction gap UG begins to form thus causing the flow of fluid  23  to be restricted in its volume and rate of flow downstream D through channel  300  thus also causing pressurized downstream flowing fluid  23  to be routed through apertures  500 . Such restricted rate or volume of flow during the course of an injection cycle, can be predetermined and controlled so as to adjustably control the rate and volume of flow of injection fluid  23  to and through the gate and into the mold cavity  80 . 
         [0068]    The controller  16  can be provided with a program that contains instructions that control the axial positioning of the surfaces  55   is  and  90   mds  relative to each other during the course of travel of the valve pin  90  such that a flow restriction UG is formed for any predetermined amount of time during the course of an injection cycle sufficient to cause fluid material  23  flow to be directed or routed through apertures  500  at a selected degree of flow. 
         [0069]    The controller  16  can be provided with a program containing instructions that control the precise axial positioning of the valve pin  90  so as to control the size of a restriction gap between surfaces  88   is  and  90   tcs  at the gate. By controlling the size of the restriction gap, the rate and volume of flow of injection fluid to and through the gate  85  can be controlled during the course of an injection cycle. 
         [0070]    Typically the rate of withdrawal of the valve pin  90  beginning from the fully closed position at the beginning of an injection cycle toward a fully gate open flow unrestricted position is carried out such that the valve pin is initially withdrawn at a reduced rate of withdrawal relative to a maximum rate of withdrawal at which the actuator is capable of driving the valve pin for a selected period of time so as to effect a rate of injection fluid flow at the beginning of an injection cycle that is less than the maximum flow rate which occurs when the valve pin is withdrawn to a position where fluid flow is unrestricted and at a maximum. Such initial reduced rate of pin withdrawal is typically selected to be at a rate and for a period of time sufficient to avoid, remove, obviate, reduce or lessen the occurrence of a blemish, artifact, overload or overpressure of injection fluid passing through the gate area at the beginning of an injection cycle. Thus the apparatus can further comprise a controller  16  containing instructions that direct withdrawal of the valve pin  90  upstream from a gate closed position at one or more reduced rates of travel relative to a maximum rate of travel upstream to one or more partially gate open positions. And the controller  16  can contain instructions that direct withdrawal of the valve pin  90  from a gate closed position upstream to one or more partially gate open positions for one or more predetermined periods of time and subsequently upstream to a fully gate open position. 
         [0071]    Alternatively the pin  90  can be controllably withdrawn upstream at a series of variable rates or positions that follow a predetermined profile of pin positions or pin velocities versus time of withdrawal. 
         [0072]    In the embodiments shown in  FIGS. 1-6 , the apparatus  5  can include a heater sleeve HS disposed around and in heat conductive engagement with the outside surface of the nozzle  50 , the sleeve including heater coils  60  typically disposed within the body of the sleeve HS.