Bag sealing system and method

Abstract

A system for sealing thermoplastic film includes one or more bag sealing units, each comprising a lower vacuum platen and a vacuum chamber cover adapted for sealing engagement on the platen to form a vacuum chamber. A sealing bar assembly includes a sealing bar designed for constant heated operation and a pair of cooling plates which function as heat sinks. The sealing bar assembly is pneumatically reciprocated between a raised, disengaged position and a lowered position with the sealing bar engaging the neck of a bag for hermetically sealing same. The cooling plates clamp the bag neck against a sealing support assembly. A method of sealing a thermoplastic film bag includes the steps of placing a packaging object in a thermoplastic bag and placing the bag on a cradle with the bag neck extending over a bag support assembly. A. vacuum chamber cover is placed on the platen and evacuated to form a vacuum chamber. A sealing bar assembly melds the thermoplastic to form a sealed area across the bag neck. A cutoff knife blade severs the end of the bag beyond a sealed area, which extends across its neck.

1 . A method of sealing thermoplastic bags, which comprises the steps of:
 providing a platen conveyor with a platen conveyor travel path;   providing a platen mounted on said platen conveyor and including an item support and a neck support;   providing said neck support with a resilient contact surface;   providing a dome conveyor with a dome conveyor travel path;   providing a dome mounted on the dome conveyor and including a vacuum chamber;   positioning said dome over said platen at a contiguous portion of said dome and conveyor travel paths;   raising said dome to a raised position spaced above said platen;   lowering said dome to a lowered position on said platen and enclosing said vacuum chamber along the contiguous portions of said travel paths;   providing said dome with a cut-off assembly including a cut-off blade;   providing said dome with a sealing assembly including a heated sealing bar and first and second cooling bars located on either side of said sealing bar;   placing a thermoplastic film bag on said item support and said neck support;   lowering said cooling bars from a raised position spaced above said bag and said neck support to a lowered position clamping a neck portion of said bag on said neck support;   lowering said sealing bar from a raised position spaced above said bag and said neck support to a lowered position engaging said bag neck portion on said neck support;   thermally and hermetically sealing said bag neck portion with said heated sealing bar in its lowered position;   lowering said cut-off blade from a raised position spaced above said bag and said neck support to a lowered position engaging and cutting said bag neck portion on said neck support;   raising said sealing bar to its raised position;   raising said cut-off blade to its raised position; and   raising said cooling bars to their raised positions.   
   
   
       2 . The method of  claim 1 , further comprising the steps of:
 providing said sealing bar with a heat source for continuously heating same; and   providing said cooling bars with a coolant source for continuously cooling same.   
   
   
       3 . The method of  claim 2 , further comprising the steps of:
 said sealing bar heat source including an electrical resistance heating element; and   said cooling bars including respective fluid passages; and   flowing said coolant through said cooling bar fluid passages.   
   
   
       4 . The method of  claim 1 , further comprising the steps of:
 spring-mounting said sealing assembly on said dome;   compressing said sealing assembly mounting springs when said seal bar and cooling bars are in their lowered positions; and   extending said sealing assembly mounting springs to move said seal bar and said cooling bars to their raised positions.   
   
   
       5 . The method of  claim 4 , further comprising the steps of:
 providing a sealing assembly air bladder connected to said dome and said sealing assembly;   inflating said sealing assembly air bladder to lower said sealing assembly from its raised position to its lowered position; and   deflating said sealing assembly air bladder to raise said sealing assembly from its lowered position to its raised position.   
   
   
       6 . The method of  claim 5 , further comprising the steps of:
 fixedly mounting said seal bar on said sealing assembly;   spring-mounting said cooling bars on said sealing assembly; and   compressing said cooling bar mounting springs and retracting said cooling bars relative to said seal bar with said cooling and seal bars in their respective lowered positions.   
   
   
       7 . The method of  claim 1 , further comprising the steps of:
 spring-mounting said cut-off assembly on said dome;   compressing said cut-off assembly mounting springs when said cut-off blade is in its lowered positions; and   extending said cut-off assembly mounting springs to move said cut-off blade to its raised position.   
   
   
       8 . The method of  claim 7 , further comprising the steps of:
 providing a cut-off assembly air bladder connected to said dome and said cut-off assembly;   inflating said cut-off assembly air bladder to lower said cut-off blade from its raised position to its lowered position; and   deflating said cut-off assembly air bladder to raise said cut-off blade from its lowered position to its raised position.   
   
   
       9 . The method of  claim 1 , further comprising the steps of:
 providing multiple said domes and platens;   providing said dome conveyor travel path with a circular configuration;   providing said platen conveyor travel path with a non-circular configuration including a contiguous portion with said platens located directly under respective domes; and   sealing said domes on respective platens in said contiguous portion of said platen conveyor travel path.   
   
   
       10 . An apparatus for sealing thermoplastic bags, comprising:
 at least one platen having a base with an upper surface;   an item support and a neck support disposed on the upper surface of said base;   said item support adapted to receive a thermoplastic bag having a neck, said neck support having a resilient contact surface adapted for receiving said thermoplastic bag neck;   at least one dome including a cut-off assembly, sealing assembly, and vacuum chamber, said dome having a lower sealing edge for sealing engagement with said platen upper surface;   a compressed air source connected to said bladder of said sealing assembly and adapted for inflating same;   said cut-off assembly having a guide rod mounting a blade, said guide rod having an air bladder connected thereto, said air bladder having a deflated configuration with said cut-off assembly in its raised position and an inflated configuration with said cut-off assembly in its lowered configuration;   a compressed air source connected to said bladder of said cut-off assembly and adapted for inflating same;   said cut-off assembly includes a spring suspension connecting said cut-off assembly to said dome, said spring suspension biasing said cut-off assembly towards its raised position and compressing with said cut-off assembly disposed in said lowered position;   said sealing assembly includes a sealing bar and cooling bars having an air bladder connected thereto, said air bladder having a deflated configuration with said sealing assembly in its raised position and an inflated configuration with said sealing assembly in its intermediate and lowered position;   said sealing bar having a heat source for continuously heating same;   said cooling bars connected to a coolant source for continuously cooling same;   said cooling bars having a lower contact surface and being disposed on opposite sides of said sealing bar communicating therebetween in a thermal exchange relationship;   said sealing bar lower contact surface spaced above said cooling bars lower contact surface when said sealing assembly is in its raised position and in its intermediate position, said sealing bar lower contact surface engaging said thermoplastic bag neck in its lowered position and clamping same against said resilient contact surface;   said cooling bars lower contact surface spaced above said thermoplastic film when said sealing assembly is in its raised position, said lower contact surface engaging said thermoplastic bag neck in its intermediate and lowered position and clamping same against said resilient contact surface;   said sealing assembly includes a spring suspension connecting said sealing assembly to said dome, said spring suspension biasing said sealing assembly towards its retracted position with said sealing assembly raised and compressing with said sealing assembly disposed in said intermediate and said lowered position; and   said cooling bars include a spring suspension connecting said cooling bars to said sealing assembly, said spring suspension biasing said cooling bars toward its retracted position with said sealing assembly disposed in said raised position and compressing with said sealing assembly disposed in said intermediate and said lowered position.