Impulse heating device for use with thermoplastic materials and method

Claim 2

An assembly for cutting plastic film by localized heating of the film above the melting temperature comprising: a. a film heater element comprising a thin ribbon of electrical resistance-heating material having opposite major surfaces and generally parallel first and second sides; b. circuit means for connecting said heater element in an electrical circuit to elevate the temperature of said element above the melting temperature of plastic film; and, c. support means for said element comprising: 1. an elongated heater element support body oriented to extend across a width of plastic film, said heater element coextending with said body; and, 2. dielectric support means between said support body and said heater element, said dielectric support means comprising support portions extending between the ends of said heater element along said major surfaces and a first side of said heater element; d. said heater element ribbon having transverse closely spaced corrugations formed substantially continuously between the ends thereof and said second side of said heater element projecting slightly from said dielectric support means; e. said second side of said heater element lying in a plane and defining an approximately sinusoidal narrow line in said plane, said heater element engageable with a plastic film along at least parts of said line to cut said film; f. heating of said heater element causing said corrugations to deepen due to thermal expansion without increasing the overall length of said heater element and said heater element being laterally supported by said dielectric means at least when heated.

Claim 3

dielectric support means between said support body and said heater element, said dielectric support means comprising support portions extending between the ends of said heater element along said major surfaces and a first side of said heater element; d. said heater element ribbon having transverse closely spaced corrugations formed substantially continuously between the ends thereof and said second side of said heater element projecting slightly from said dielectric support means; e. said second side of said heater element lying in a plane and defining an approximately sinusoidal narrow line in said plane, said heater element engageable with a plastic film along at least parts of said line to cut said film; f. heating of said heater element causing said corrugations to deepen due to thermal expansion without increasing the overall length of said heater element and said heater element being laterally supported by said dielectric means at least when heated.

Claim 4

dielectric support means between said support body and said heater element, said dielectric support means comprising support portions extending between the ends of said heater element along said major surfaces and a first side of said heater element; d. said heater element ribbon having transverse closely spaced corrugations formed substantially continuously between the ends thereof and said second side of said heater element projecting slightly from said dielectric support means; e. said second side of said heater element lying in a plane and defining an approximately sinusoidal narrow line in said plane, said heater element engageable with a plastic film along at least parts of said line to cut said film; f. heating of said heater element causing said corrugations to deepen due to thermal expansion without increasing the overall length of said heater element and said heater element being laterally supported by said dielectric means at least when heated.

Claim 5

The assembly claimed in claim 1 wherein said support body is composed of material having a relatively large heat conductivity for transferring heat from said heater element and said dielectric support means.

Claim 6

a heating element defined by a transversely corrugated ribbon having a relatively large electrical resistance, said heating element partially disposed in said groove and extending along said groove in a path substantially parallel to sides of said groove;

Claim 7

a heating element defined by a transversely corrugated ribbon having a relatively large electrical resistance, said heating element partially disposed in said groove and extending along said groove in a path substantially parallel to sides of said groove;

Claim 8

at least one dielectric body in said groove between said heating element and said support member, said at least one body extending along opposed faces of said heating element for laterally supporting said heating element;

Claim 9

at least one dielectric body in said groove between said heating element and said support member, said at least one body extending along opposed faces of said heating element for laterally supporting said heating element;

Claim 10

An assembly as claimed as in claim 2 wherein said dielectric support means is deflectible to enable movement of said heater element corrugations relative to said support body in response to thermal expansion and contraction of the material forming said heater element.

Claim 11

An assembly as claimed in claim 1 wherein said heater element is comprised of a nickel-chromium alloy and has a thickness which is extremely small in relation to its width.

Claim 12

said element projecting from said support member toward said other jaw to define a substantially planar nonlinear plastic heating surface portion.

Claim 13

said element projecting from said support member toward said other jaw to define a substantially planar nonlinear plastic heating surface portion.

Claim 14

In an apparatus for heating plastic film: a. a first support member constructed from a material having a relatively high heat conductivity; b. a heater element comprising a thin ribbon of resistance-heating material supported by said member with a side surface portion of said element projecting away from said member, said heater element extending linearly throughout its length along said support member; c. at least one body of dielectric material between said element and said member, said at least one body in heat exchange relationship with said element and said member and extending along faces of said heater element for maintaining said one surface portion of said element in position; d. said element defining corrugations having crests extending transversely to said one surface portion; e. a second support member defining a pressure surface spaced from said one surface portion of said element; and, f. means for effecting relative movement between said first and said second support members whereby at least a part of said one surface portion engages film between said element and said opposed pressuRe surface along at least one nonlinear, narrow line of engagement.

Claim 15

In an apparatus for heating plastic film: a. a first support member constructed from a material having a relatively high heat conductivity; b. a heater element comprising a thin ribbon of resistance-heating material supported by said member with a side surface portion of said element projecting away from said member, said heater element extending linearly throughout its length along said support member; c. at least one body of dielectric material between said element and said member, said at least one body in heat exchange relationship with said element and said member and extending along faces of said heater element for maintaining said one surface portion of said element in position; d. said element defining corrugations having crests extending transversely to said one surface portion; e. a second support member defining a pressure surface spaced from said one surface portion of said element; and, f. means for effecting relative movement between said first and said second support members whereby at least a part of said one surface portion engages film between said element and said opposed pressuRe surface along at least one nonlinear, narrow line of engagement.

Claim 16

Apparatus as claimed in claim 5 wherein said line of engagement is approximately sinusoidal whereby film adhered to said surface portion is separated therefrom by a shearing action when the film is pulled.

Claim 17

Apparatus as claimed in claim 5 and further including structure for rotating one of said first and second bodies to establish contact between said heater element and film at a plurality of spaced locations defined by crests of said corrugations.

Claim 18

In an apparatus for heating thermoplastic material: a. first and second jaws spaced apart to define a space therebetween in which at least one sheet of plastic material is insertable; b. mechanism supporting one of said jaws for movement toward and away from said other jaw whereby plastic material in said space is engaged between said jaws; c. one of said jaws including:

Claim 19

In an apparatus for heating thermoplastic material: a. first and second jaws spaced apart to define a space therebetween in which at least one sheet of plastic material is insertable; b. mechanism supporting one of said jaws for movement toward and away from said other jaw whereby plastic material in said space is engaged between said jaws; c. one of said jaws including:

Claim 20

Apparatus as claimed in claim 8 wherein one of said jaws is supported by mounting means for adjustably positioning the angle of the plane of said heating surface relative to the other jaw.

Claim 21

Apparatus as claimed in claim 9 wherein the other of said jaws includes a resiliently deflectible pressure pad engageable with the plastic material to urge the plastic material against said heating surface.

Claim 22

Apparatus as claimed in claim 9 wherein said mounting means includes relatively movable parts for adjustably positioning the plane of said heating surface to intersect said plastic material whereby said element heats the plastic adjacent crests of said corrugations to produce spaced perforations in the plastic material.

Claim 23

Apparatus as claimed in claim 11 wherein said plastic material is defined by two plies of plastic film, said heating element engaging said film to form said perforations and for heating said film at least adjacent said perforations to seal said plies together on opposite sides of said perforations.

Claim 24

An electrical heater assembly for cutting plastic sheets or film by heating the plastic material above its melting temperature along at least one narrow line of contact comprising: a. an elongated support body positioned to extend across a plastic sheet or film and having ends projecting beyond opposite sides of a sheet or film; b. a thin ribbon of electrical resistance heating material extending along said support body, said ribbon having ends adjacent respective ends of said support body and defining opposed faces having substantially parallel first and second sides and oriented with respect to said body member so that said first side projects from said body toward a plastic sheet or film for engagement therewith along the line of contact; c. means defining an electrical circuit connected to said ribbon for establishing electrical current flow through said ribbon to heat the ribbon to a temperature substantially above the melting temperature of a plastic film or sheet; d. dielectric support means between said support body and said ribbon, said dielectric support means comprising support portions extending substantIally along the lengths of said ribbon faces and from said second side along said faces toward said first side so that said ribbon is laterally supported by said portions; e. said ribbon further defining closely spaced corrugations extending transversely to said first and second sides for stiffening said ribbon, said corrugations formed substantially continuously throughout the length of said ribbon whereby said first side of said ribbon is approximately sinusoidal; and, f. said first side of said ribbon projecting from said dielectric support means for contact with a plastic sheet or film.

Claim 25

An electrical heater assembly for cutting plastic sheets or film by heating the plastic material above its melting temperature along at least one narrow line of contact comprising: a. an elongated support body positioned to extend across a plastic sheet or film and having ends projecting beyond opposite sides of a sheet or film; b. a thin ribbon of electrical resistance heating material extending along said support body, said ribbon having ends adjacent respective ends of said support body and defining opposed faces having substantially parallel first and second sides and oriented with respect to said body member so that said first side projects from said body toward a plastic sheet or film for engagement therewith along the line of contact; c. means defining an electrical circuit connected to said ribbon for establishing electrical current flow through said ribbon to heat the ribbon to a temperature substantially above the melting temperature of a plastic film or sheet; d. dielectric support means between said support body and said ribbon, said dielectric support means comprising support portions extending substantIally along the lengths of said ribbon faces and from said second side along said faces toward said first side so that said ribbon is laterally supported by said portions; e. said ribbon further defining closely spaced corrugations extending transversely to said first and second sides for stiffening said ribbon, said corrugations formed substantially continuously throughout the length of said ribbon whereby said first side of said ribbon is approximately sinusoidal; and, f. said first side of said ribbon projecting from said dielectric support means for contact with a plastic sheet or film.

Claim 26

An assembly as claimed in claim 13 further including connectors at opposite ends of said ribbon for nonresiliently anchoring said ribbon ends to said support body.