Sealing device for plastic sheet material

Claim 2

Means for heat sealing thin layers of plastic wrap comprising, a normally horizontal base, a long thin metal blade, means for supporting said metal blade in a vertical plane with the edges horizontal above said base, said blade supporting means permitting blade movement through a limited vertical distance, an electric heating element attached to said metal blade for heating the same, means for maintaining said blade in a normal down position with reference to the base, means including a crank for cooperating with said blade to move the same vertically from its normal down position upon crank operation, said blade moving means having stable positions when said blade is in its normal bottom position and being movable through an operating cycle during which said blade is moved upwardly to an unstable top position and then down to its normal stable position, a housing carried by said base and disposed over said blade and base, said housing having the top portion thereof provided with a longitudinal gap disposed above the top edge of said blade and toward which said blade is moved during crank operation to dispose the blade edge in said gap, a press bar assembly carried by said housing on the outside thereof and movable toward and away from the housing gap, said press bar assembly including locking means on said housing for maintaining said press bar assembly down against the housing gap, said press bar assembly including a layer of soft material to which plastic sheet wrap will not stick, said press bar assembly when locked over said housing gap being adapted to back work to be heat sealed, said blade being adapted to be momentarily pressed against the work during a crank operating cycle, said layer of soft nonstick material in said press bar assembly and blade edge momentarily pressing the work therebetween so that when said blade is hot, effective plastic heat sealing is accomplished without damage to the work.

Claim 3

The construction according to claim 1 wherein said heat insulating material in said press bar assembly bulges outwardly to push work into the gap in preparation for heat sealing.

Claim 4

The construction according to claim 2 wherein said means for moving said metal blade vertically includes an overcenter crank means.

Claim 5

A heat sealing mechanism comprising, a flat elongated base plate, a housing including end portions carried by said base plate, a pair of guide plates at each housing end portion, a thin elongated metal blade normally disposed in a generally vertical plane with a free edge at the top of said blade extending horizontally, said blade having the end portions disposed between said guide plates for limited movement vertically to and from said base plate, an electric heating element carried by said metal blade for heating said blade to a desirable plastic wrap heat sealing temperature, at least one rocker arm carried by said base plate for engaging the bottom edge of said metal blade, said rocker arm being movable about a generally horizontal axis, a crank rod carried by said base along the length thereof and having a laterally offset portion below said rocker arm for raising said rocker arm and permitting it to drop, spring means for biasing said blade to a down position, a handle for said crank rod to cause said offset portion to rock said arm for elevating and dropping said blade, said crank and rocker arrangement being unstable in any position except the normal down position of said rocker arm and blade, said housing having a gap above said blade for the length thereof, said blade being so positioned that in the up position of said blade the free edge thereof extends into the gap of said housing, a press bar assembly, means for pivotally securing said press bar assembly at one housing end portion for movement toward and away from said gap, said press bar assembly being so dimensioned and positioned that when it is moved to the down position toward said gap, said assembly will cover said gap above the free edge of said blade, means for locking the free end of said press bar assembly in position so that the entire length of the press bar assembly extends along the housing and covers the gap, soft heat insulating nonstick means carried by said press bar assembly and adapted to provide a backing against which a hot blade edge may press plastic wrap to be heat sealed without sticking to said press bar assembly, said work to be heat sealed being adapted to be locked between said press bar assembly and housing above said gap, whereby when said metal blade is in heat sealing condition it is momentarily pushed upwardly into position to press against the work, after which the blade is dropped away from the gap due to the unstable condition of said blade actuating means.

Claim 6

A heat sealing mechanism comprising, a flat elongated base plate, a housing including end portions carried by said base plate, a pair of guide plates at each housing end portion, a thin elongated metal blade normally disposed in a generally vertical plane with a free edge at the top of said blade extending horizontally, said blade having the end portions disposed between said guide plates for limited movement vertically to and from said base plate, an electric heating element carried by said metal blade for heating said blade to a desirable plastic wrap heat sealing temperature, at least one rocker arm carried by said base plate for engaging the bottom edge of said metal blade, said rocker arm being movable about a generally horizontal axis, a crank rod carried by said base along the length thereof and having a laterally offset portion below said rocker arm for raising said rocker arm and permitting it to drop, spring means for biasing said blade to a down position, a handle for said crank rod to cause said offset portion to rock said arm for elevating and dropping said blade, said crank and rocker arrangement being unstable in any position except the normal down position of said rocker arm and blade, said housing having a gap above said blade for the length thereof, said blade being so positioned that in the up position of said blade the free edge thereof extends into the gap of said housing, a press bar assembly, means for pivotally securing said press bar assembly at one housing end portion for movement toward and away from said gap, said press bar assembly being so dimensioned and positioned that when it is moved to the down position toward said gap, said assembly will cover said gap above the free edge of said blade, means for locking the free end of said press bar assembly in position so that the entire length of the press bar assembly extends along the housing and covers the gap, soft heat insulating nonstick means carried by said press bar assembly and adapted to provide a backing against which a hot blade edge may press plastic wrap to be heat sealed without sticking to said press bar assembly, said work to be heat sealed being adapted to be locked between said press bar assembly and housing above said gap, whereby when said metal blade is in heat sealing condition it is momentarily pushed upwardly into position to press against the work, after which the blade is dropped away from the gap due to the unstable condition of said blade actuating means.

Claim 7

The construction according to claim 4 wherein said nonstick mateRial in said press bar assembly is a plastic of the group consisting of silicone rubber and Teflon.

Claim 8

The construction according to claim 2 wherein said heating element is secured to the lower part of the blade and wherein thermostatic switch means are provided to maintain said blade temperature at a desired value.