CA2545440A1

CA2545440A1 - Vertical oven plastic vacuum forming machine

Info

Publication number: CA2545440A1
Application number: CA 2545440
Authority: CA
Inventors: William Mccurdy
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-05-03
Filing date: 2006-05-03
Publication date: 2007-11-03

Abstract

A vertical forming machine using ambient temperature and fired by low cost natural gas, propane, etc. built to shape difficult, dissimilar materials. The machine will laminate arrangements of shaped materials easily. Example: Foam plastic laminated to rigid plastic. The vertical arrangement will allow for twin sheet forming with minimal setup.

Rapidly moving air will heat the plastic material and dual air-flow system allows for faster production with materials being formed heated evenly throughout sheet.
Shaping of sheet plastic is accomplished with a unique vertical mould system complete with controlled advance and all forming taking place inside a narrow air stream, centrally positioned inside oven.

Doors in front and back of oven open and close to permit access of forming moulds.
Door also at both ends of oven to permit entry of sheet and exit of forming.
Uneven heating or over-heating of sheet is eliminated when using this vertical controlled-heat oven.

Description

SPECIFICATION
In most production using thermoplastic sheet the plastic is heated horizontally and is clamped firmly on four-sides with moulds entering from bottom and top in a special forming area (not the actual heated oven). In order to reach this forming and cooling position the plastic must be moved, losing heat and time in the moving.

Radiant heat elements are used to heat the sheet evenly and rapidly to the core.
Since radiant heat only heats the surface and slowly works its way through the sheet, the slowness of heat-speed through the sheet causes a problem when using radiant heat (in that the surface of plastic can get over-heated easily). Sag of sheet during heating occurs and presents a major problem when shaping in large flat areas.
Whereas, a vertical sheet is always presented to the forming area as flat.

Production losses can also happen when uneven heat or overheating occurs in the sheet due to poor sheet materials, varying thicknesses, sheet-sagging, etc.
Polycarbonate plastic has to be dried before forming in order to eliminate moisture bubbles that occur when heating and the cooling process is very fast.
Polycarbonate can now be processed in our vertical oven without drying, because the moisture is eliminated slowly, and forming can take place within the heated air stream.
This procedure of forming in heat eliminates the fast-cooling problem occurring during transferring plastic from oven to forming area.

In addition, our system of heating with ambient air temperature, allows plastic to soak in the heat at forming temperature, with no spoilage due to uneven or overheating of the material being formed.

This superior system of heating and forming, allows for heating a wide variety of dissimilar materials such as plastic, foam, rubber, wood, foam insulation, etc. Not possible with regular system.

Page-4-Furthermore, over-heating of the plastic sheets are reduced and consequently, spoilage is reduced. Ability in this machine to combine the plastics in a "laminated arrangement" allows engineering to use materials together for strength insulation appearance etc. Structures of metal wood can also be easily combined in this vertical machine.

DESCRIPTION
Very narrow oven (figure) to hold vertical sheets and to heat uniformly one sheet of plastic (figure2) for standard forming or two sheets for twin sheet production which can double the speed of production since two sheets can be shaped at one time using female moulds.

Heater (figure3) will heat air in the oven to production temperature. Blowers (figure'o) will circulate heated air passing through main oven and motors (figure12), will ultra-rapidly circulate through the forming cooling section of oven. Forming and cooling area may be isolated from general oven by closing top shut off (figure13) and bottom shut off (figure14). Eliminating ultra-rapid air-curtain, and allowing two separate systems of air circulation, regular oven and air-curtain. The two systems speed up the time required to heat sheets to process temperature, by saving heated air stored in regular oven.

Counter-balanced doors (figure") front and back (figure5) will be opened and closed by a motor (figure1) allowing female mould (figure6) and male mould to proceed forward into soft plastic sheet (figure') and with pressure applied on plastic and the application or vacuum on mould and vacuum in a sealing channel around perimeter of mould to hold plastic tightly to mould until cooled.

Page - 5 -Forming of plastic takes place inside narrow oven and plastic may be easily loaded from front of machine or loaded from end of machine, unload of finished part can be from front or out opposite end of machine.

This machine is designed for using low cost energy such as gas or propane.
However heating of plastic can be speeded up by installing radiant energy electric heaters in door panels front or back. Control of this radiant energy in zones can also adjust heat over surface of plastic.

The vertical configuration of forming allows the operator to soak the plastic in the forming temperature for more even heat subsequently better forming less spoilage.
Inside the vertical machine centrally located in the middle of the narrow plastic heating air stream is a non-moving but adjustable fixed frame (figure8). This frame allows clamping of plastic and with the addition of proper jigs, the ability to position reinforcing structures (wood, metal, plastic) to be built into product with plastic sheet finish applied on one or two sides. Example: pontoons, tanks, airplane wings, etc.).
This vertical machine forming in oven is an advanced tool for the plastic sheet processor. With built-in versatility and superior performance when handling large formings, and the machine is capable of laminating dissimilar materials before moulding into products.

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Claims

CLAIM 1: Narrow vertical oven consisting of counter-balanced doors both front and back for mould access, and two ends allowing material to access and finished product to exit, and a curtain of heated air where plastic is heated and formed.
CLAIM 2: Dual system of moving air in oven consisting of regular oven air circulation up to required forming temperature and an air curtain of rapidly moving air which can be separated from main flow, during forming and cooling of plastic.
CLAIM 3: Moulds capable of entering oven from two sides front and back, consisting of a structure wherein moulds are moved into the soft plastic from one or two sides and are guided into forming position where they may be locked into position while extreme pressure is applied to shape and to detail the sheet plastic.
CLAIM 4: Fixed frame in oven consisting of four sides adjustable to different sizes.
No four-sided clamps on frame are required. Moulds will clamp plastic to this frame and vacuum channel (figure'A') will help ensure proper vacuum seal for mould on plastic so that vacuum can shape plastic. This fixed frame can be arranged to hold reinforcing frames that can be incorporated in twin sheet or single sheet forming.
NOTE: The vacuum channel in mould is important in large forming where plastic shrinkage is a problem, due to vacuum seal leakage.
CLAIM 5: Laminating of material in vertical oven consisting of a fixed frame wherein different materials are hung in oven to heat then pressed together to eliminate air and to finally form into female mould using vacuum and pressure.
CLAIM 6: Straight through production consisting of a preheat oven holding multiple sheets arranged to be fed into narrow oven through end door in the narrow oven, and processed with minimal heat-time.

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