Patent Publication Number: US-2012034332-A1

Title: Hot-runner system having bladder assembly

Description:
TECHNICAL FIELD 
     Embodiments of the present invention generally relate to hot-runner system used in an injection molding system. 
     BACKGROUND OF THE INVENTION 
     Examples of known molding systems are (amongst others): (i) the HyPET (TRADEMARK) Molding System, (ii) the Quadloc (TRADEMARK) Molding System, (iii) the Hylectric (TRADEMARK) Molding System, and (iv) the HyMet (TRADEMARK) Molding System, all manufactured by Husky Injection Molding Systems Limited (Location: Bolton, Ontario, Canada; www.husky.ca). 
     SUMMARY OF THE INVENTION 
     The invention is set forth and characterized in the main claim(s), while the dependent claims describe other characteristics of the invention. 
     More and more, customers doing precision molding are calling for “synchronous” valve pin actuation for their valve gated hot runners. The valve pins move together as they are attached to a single plate that moves back and forth. Plate actuated systems are commercially available that use either hydraulics or electric motors to move the plate. While these methods of actuation may work well for some applications, some molding shops may still be best suited for pneumatic plate actuation. 
     The purpose of the present invention is to provide a means for pneumatically actuating an actuation plate that drives valve pin(s) stroke, opening and closing flow path(s) to a mold assembly. Both hydraulics and electric motors have been used as a means for actuation. Systems with hydraulic actuation use a number of piston assemblies that push or pull the plate. These hydraulic piston assemblies can consume a lot of space in the hot runner, apply uneven loads to the plate (could cause binding) and may also require unwanted maintenance. Systems using an electric motor to actuate the plate typically have belt, gear or ball screw drives that move the plate using some form of cam mechanisms. These systems are costly and can be prone to premature wear/failure. 
     In sharp contrast, the aspects of the present invention may use an inflatable actuator device (also called a “bladder” or “bladder unit”) to move the actuation plate, which provides a simple, cost effective and robust solution to valve pin plate actuation. 
     Therefore, a general aspect of the invention is to provide a hot-runner system ( 100 ), including: a support structure ( 102 ); an actuation plate ( 106 ) being movable relative to the support structure ( 102 ); and a bladder assembly ( 108 ) being installed between the actuation plate ( 106 ) and the support structure ( 102 ). 
     These and other aspects and features of non-limiting embodiments of the present invention will now become apparent to those skilled in the art upon review of the following description of specific non-limiting embodiments of the invention in conjunction with the accompanying drawings. 
    
    
     
       DETAILED DESCRIPTION OF THE DRAWINGS 
       The invention and its embodiments will be more fully appreciated by reference to the following detailed description of illustrative (non-limiting) embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  depicts a schematic representation of a cross section of a hot-runner system  100 ; and 
         FIG. 2  depicts a perspective view of the hot-runner system  100  of  FIG. 1 . 
     
    
    
     The drawings are not necessarily to scale and may be illustrated by phantom lines, diagrammatic representations and fragmentary views. In certain instances, details that are not necessary for an understanding of the embodiments or that render other details difficult to perceive may have been omitted. 
     DETAILED DESCRIPTION OF THE NON-LIMITING EMBODIMENT(S) 
     Reference will now be made in detail to the non-limiting embodiment(s) of the present invention. The hot-runner system  100  may include components that are known to persons skilled in the art, and these known components will not be described here; these known components are described, at least in part, in the following reference books, for example: (i) “Injection Molding Handbook” authored by OSSWALD/TURNG/GRAMANN (ISBN: 3-446-21669-2), (ii) “Injection Molding Handbook” authored by ROSATO AND ROSATO (ISBN: 0-412-99381-3), (iii) “Injection Molding Machines” 3rd Edition 3rd Edition authored by JOHANNABER (ISBN 3-446-17733-7) and/or (iv) “Runner and Gating Design Handbook” authored by BEAUMONT (ISBN 1-446-22672-9). 
       FIG. 1  depicts the schematic representation of the cross section of the hot-runner system  100 . The hot-runner system  100  includes (but is not limited to): (i) a support structure  102 , (ii) a valve pin  104 , (iii) an actuation plate  106 , and (iv) a bladder assembly  108 . The valve pin  104  is movable relative to the support structure  102 . The actuation plate  106  is movable relative to the support structure  102 . The actuation plate  106  is connected with the valve pin  104  (via a pin coupler  105 ). The bladder assembly  108  is installed between the actuation plate  106  and the support structure  102 . The bladder assembly  108  includes: (i) a first bladder unit  110  located on a first side of the actuation plate  106  and a second bladder unit  112  located on a second side of the actuation plate  106 . The actuation plate  106  is movable along a direction or a stroke  114 . To move the valve pin  104  to the valve-closed position, the first bladder unit  110  is inflated with a pressurized fluid (such as, pressurized air, etc) while the second bladder unit  112  is not pressurized, and as a result the first bladder unit  110  becomes inflated and pushes the actuation plate  106  to the right side of  FIG. 1  so as to move the valve pin  104  toward the valve-closed position. To move the valve pin  104  to the valve-opened position, the first bladder unit  110  is depressurized while the second bladder unit  112  is pressurized with a fluid, and as a result the first bladder unit  112  becomes inflated and pushes the actuation plate  106  to the left side of  FIG. 1  so as to move the valve pin  104  toward the valve-opened position. 
     The bladder units  110 ,  112  include a thin, flexible walled pressure vessel that is inflatable with a high-pressure fluid such that the vessel volume expands. The pressure vessel is constrained in such a way as to translate its change in volume to a force applied in an intended direction. The inflatable actuators (also called “pressure vessel”) may be placed on one or both sides of the actuation plate  106 , moving the actuation plate  106  back and forth as the pressure vessel(s) are inflated and deflated. This type of actuation system is cost effective and requires very little maintenance. More importantly, since the pressure vessel applies the actuation force over a broad area of the actuation plate  106 , the actuation plate  106  and the guidance system of the actuation plate  106  are exposed to more uniform forces, thus leading to less bushing wear and lower potential for plate binding. 
     It will be appreciated that  FIG. 1  appears to show the valve pin  104  passing through the bladder assembly  108 , which is not intended. It is preferred that the valve pin  104  does not extend through a bladder unit of the bladder assembly  108 .  FIG. 1  depicts at least part of the valve pin  104  in phantom lines, and it will be appreciated this is not intended to depict the valve pin  104  as supposedly passing through the middle of the bladder unit  112 , but rather there are bladder units  112  is positioned on either side of the valve pin is positioned on either side of the valve pin  104 , with the valve pin  104  passing by the bladder units  112  so positioned on either side of the valve pin  104 . The configuration as illustrated in  FIG. 1  would require either: (i) more than one bladder unit (with the valve pin spaced between the bladder units), or (ii) the valve pin  104  is offset from a single bladder unit  112 . It will be appreciated that a number of valve pins  104  may be connected to the actuation plate  106 . The bladder units  110 ,  112  are inflatable and deflatable, and the valve pins  104  may be attached to each side of the actuation plate  106 , such that when one bladder is inflated with a high-pressure fluid, the actuation plate  106  is pushed to the opposite side thus moving the valve pins  104  to close the flow path into a mold assembly (not depicted but known). When the second bladder unit  112  is inflated with high pressure fluid and the first bladder unit  110  is deflated, the actuation plate  106  is pushed to the opposite side thus moving the valve pins  104  to open the flow path into the mold assembly. 
       FIG. 2  depicts a perspective view of the hot-runner system  100  of  FIG. 1 . It will be appreciated that  FIG. 2  appear to depict the rightmost row of valve pins  104  (also called valve stems) terminating in the middle of the lower bladder unit, and it will also be appreciated that the valve pins  104  pass beside the bladder (that is, the pins  104  do not terminate in the lower bladder unit). The portion of the pins  104  depicted as extending below the rightmost row of valve pins  104  is merely the connection of the pins  104  to the actuation plate  106 .  FIG. 2  depicts an arrangement of bladder units  110 ,  112  in which two columns with four rows of valve pins  104  are attached to the actuation plate  106 , and multiple bladder units  110 ,  112  are spaced between the valve pins  104 .  FIG. 2  depicts an example of a configuration with the multiple bladder units, which provides a way to ensure that all the bladder units actuate in synchronization so as not to inadvertently cock the actuation plate  106 . It will be appreciated that there will inevitably be slight differences in the inflation of each bladder unit. It is preferred to provide consistent air supply from the hot-runner plates (or the injection-molding system) to each bladder unit. Ideally, there should be no constrictions within the bladder units (thus ensuring good flow), no static friction to overcome or any stick/slip action (thus as there would be on pneumatic or hydraulic pistons). Side walls of the bladder units are designed to be stiff enough such that each bladder unit will fill evenly bearing against the actuation plate  106  with a broad surface area. Although it will likely not be possible to provide absolutely synchronous bladder inflation, it will be significantly better than two point loads applied by pneumatic or hydraulic pistons. 
     In accordance with another non-limiting embodiment, only one bladder unit  110  is attached to one side of the actuation plate  106 . As the bladder unit  110  is inflated, the bladder unit  110  moves the actuation plate  106 , opening or closing mold gates with the valve pins  104 . When the bladder unit  110  is deflated, the return motion of the actuation plate  106  may be performed by a preloaded spring (not depicted) that is (not depicted) that is coupled to the actuation plate  106 . Air hoses  120  connect the bladders  110 ,  112  to the pressurized fluid. 
     It is noted that the foregoing has outlined some of the more pertinent non-limiting embodiments of the present invention. This invention may be used for many applications. Thus, although the description is made for particular arrangements and methods, the intent and concept of the invention is suitable and applicable to other arrangements and applications. It will be clear to those skilled in the art that modifications to the disclosed non-limiting embodiments can be effected without departing from the spirit and scope of the invention. The described non-limiting embodiments ought to be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be realized by applying the disclosed invention in a different manner or modifying the invention in ways known to those familiar with the art. This includes the mixing and matching of features, elements and/or functions between various non-limiting embodiments is expressly contemplated herein, unless described otherwise, above.