GB2111894A

GB2111894A - Edge protector manufacture

Info

Publication number: GB2111894A
Application number: GB08136029A
Authority: GB
Inventors: Leslie Harold Edward Bailey
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-30
Filing date: 1981-11-30
Publication date: 1983-07-13

Abstract

In a process for the manufacture of individual edge protectors a maleable hot plastic sheet from an extruder head is passed into a thermoforming machine which has male and female forming blocks (C & d), and prongs (2) which when closed press strap retaining ridges, on to the top of the plastic angle from the underside. The forming blocks continue to travel the length of the machine, allowing the plastic to set, and return again to the original start position, making the process continuous. The formed sheet so made is cut into lengths the extruded thermoplastic sheet can vary in material, width, and thickness. <IMAGE>

Description

SPECIFICATION Plastic edge protector thermoforming process The purpose of this Application is to try and secure Patent protection on product and/or process.

The product is called an edge protector (sheet 1/4) and is used by persons who use plastic and or steel strapping to secure goods to pallets, or any other application where edge protection is required. The edge protector stops strapping from cutting into pallets thus allowing load to become loose, or indeed just stop the strapping from damaging the product.

Protection is achieved by slipping the edge protector under the strapping on pallet or goods corner prior to final tensioning. Our product is equiped with a single strip of double sided adhesive tape on the underside of one of the edge protector legs. This facility is very usefull when edge protection is required to be used in a position where it cannot be held by hand. By removal of the backing strip on the adhesive tape, the edge protector can be placed and held in position, prior to, and during the strapping operation. The edge protector is equipped with two raised ridges which are used as strap retainers.

The process that we are seeking protection for is totaly different from the current method of production, which is injection moulding. The first piece of equipment in the production line is an thermoplastic extruder. This machine will take our plastic raw material granuals and extrude it from the die head in the form of a flat strip. As the strip emerges, very hot and malleable, it is fed through forming plates which maintain width and thickness required, thereafter it is fed into the thermoforming machine which is the key part of the process, in that it will pull the plastic from the extruder, through the forming plates, fold the strip into a 900 angle and press the strap retaining ridges into the formed angle from the underside, also removing the heat at the same time, so that when it emerges from the machine it is set hard.

From the thermoforming machine the continuous length of edge protectors are fed into a cropping machine, where first of all a double sided strip of adhesive tape is automaticaly applied onto the underside. The plastic then continues into the cropping machine where it is cut into exact 38mm lengths, with the strap retaining ridges equispaced from each end.

We propose to make this product from the following plastic materials UPVC, low and high density polythene and polypropylene.

The method used by manufacturing industry at the moment to produce edge protectors is for them to be injection moulded. Depending on the size of the edge protector and the moulding machine, controls the number of pieces that can be made in one shot.

This method involves two dies with the edge protector forms machined into them. The dies are pressed together under hydraulic pressure, prior to molten thermosetting plastic being injected into them filling the cavitys. The dies are then opened, allowing the pieces connected to the sprue to be removed. Plastic material normaly used for this product when injection moulded, is low and high density polythene.

Actual process and method of manufacture for our product is as follows.

Many types of plastic can be used in our process, the main one's being UPVC, high and low density polythene and polypropylene. The plastic granuals will be fed into an thermoplastic extruder which will convert them into an homogenous gel which is extruded through a die to form a flat strip of the required dimensions. Various dies will be required, one for each size of edge protector which will vary in leg length and thickness.

The extruder has four heating zones along the barrel length, which are electronicaly controled to maintain the required temperature profile. The temperature range that we will operate in is from 1 35 C-1 90 C.

When the extruded strip emerges from the die very hot and maleable, it is drawn by hand through sizing plates which control the width and thickness.

The first sizing plate is positioned four inches from the extruder die, additional plates follow thereafter, distance and quantity as required, all within two feet of the first plate.

The strip is now fed into the thermoforming machine which is positioned directly after the sizing plates.

The thermoforming machine consists of two horizontaly mounted booms one above the other. The booms have a front and back plate (f sheet 2/4) made of steel. At each end and in between the plates of the booms are two chain sprockets (e sheet 2/4). Around the sprockets and running the length of each boom are fitted four 3/4" pitch chains of 44 links each, (h sheet 2/4), quantity of links is variable.

Across the width of each boom and joining each opposite chain link (h sheet 2/4) is fitted an aluminium carrier plate (b sheet 2/4). The carrier plate is fitted with a stub pin (0 sheet 2/4), at each end which passes through chain attachment (k sheet 2/4) this allowing the carrier plate to pivot. Each carrier plate is 38mm wide which corresponds to two 19mum pitches of the chain, therefore with 44 carrier plates fitted to the 88 pitch length chains on both booms.

They become a solid mass of plates (b 3/4).

Each carrier plate (b sheet 2/4) is fitted with its own forming tool. The female forming tool (c sheet 2/4) fitted to the upper boom, the male forming tool (d 2/4) is fitted with two forming prongs (1 sheet 2/4 and 3/4). The forming prongs fit into two slits machined into the female forming tool (c sheet 2/4 and 3/4). The slits in forming tool (c) are three times as wide as the forming prongs on tool (d) thus allowing plenty of clearance each side of the forming prong when the tools come together (sheet 3/4).

The bearing guides (g sheet 3/4) are so positioned that when roller bearings (a 3/4) make contact a ramp is created from the centreline of the chain sprocket (e) to the begining of bearing guide (g). In between the chain sprockets on both booms will be fitted guides which will locate in slots in the base of carrier plates (b sheet 2/4).

The guides will slowly locate in each carrier plate as it is moved around tile sprockets by the chains (sheet 3/4,) by the time each carrier plate and forming tool assembly has reached the centreline of the chain sprockets, the guides will have perfectly aligned the forming tools in the verticle position, and with each other.

As forming tool (d 3/4) climbs up the ramps on the lower boom, and forming tool (c sheet 3/4) climbs down the ramps on the top boom, the tools come together, reaching the final closed position on reaching bearing guide (g sheet 3/4).

The operation explained is for the plastic entry end of the thermoforming machine, the exit end of the machine operates on exactly the same principle, except that the forming tools open.

Both booms are fitted to one vertical steel pillar.

Each boom has bearing slides which locate on guides fitted to the pillar. Each boom is independantly adjustable up and down, thus infinite adjustment is available to obtain the correct gap between forming tools (c and d 2/4.) The forming tools and carrier plates are made from aluminium thus acting as heat sinks to remove the heat from the formed plastic angle.

Mechanical drive for both booms is achieved by driving a single vertical shaft via a gearbox and variable speed controler. The shaft passes through a bevel gearbox on each boom which is connected to chain sprocket shafts. (m sheet 2/4).

Operation of the machine is achieved by first adjusting the booms open so that there is approximately a two inch gap between forming tools (c and d sheet 2/4). The continuous length of extruded strip is fed by hand through the length of the booms, at this point the thermoforming machine is started and the gap between tools (c and d) closed until they just nip the plastic strip. Now the machine is pulling the strip through the forming plates from the extruder.

Various guides are fitted at the entrance to the machine to assure perfect alignment. The booms are now closed further until the gap between forming tools (c and d) corresponds to the exact thickness of the plastic strip. The strip has now been formed into a 90 right angle, and the forming prongs (1 sheet 2/4 and 3/4) have forced the plastic into the grooves in forming tool (c sheet 3/4) thus forming strap retaining ridges on the top of the angle. The plastic now stays clamped between the forming tools while it travels the length of the booms. The aluminium removing the heat from the plastic.

The length of the forming tools in this instance 38mm, corresponds to the finished cut piece of edge protector. This length is variable depending on size of product required. The continuous length of formed edge protectors are now equiped with a strip of double sided adhesive tape which is automaticaly applied as the edge protectors are fed into the cropping machine where they are cut into 38mm pieces.

Variable lengths of edge protectors can be produced by this process, made up in multiples of 38mm, or whatever length the forming tools happen to be. Thus, if the cropping machine is set to cut edge protectors 76mm long, which is the equivalent to two forming tools side by side, we now have a choice regarding the positioning of strap retaining ridges due to the fact that forming prongs (1 sheet 3/4) are detachable. We can either remove the two inner forming prongs leaving strap retaining ridges at each end of the extra long edge protector, or remove the end forming prongs leaving the two inner one's. Many variations of the product can be achieved in this manner.

Claims

1. A process for the production of a continuous length of thermoformed plastic angle, with thermoformed ridges pressed into it. Substantialyflat plastic material in strip form is taken from an extruder head in a hot and maleable condition, then passed in the extruded direction into the thermoforming machine, the machine is then closed until the forming blocks just nip the plastic strip, the strip is then pulled through forming plates at the entrance to the machine and folded to a 900 angle, various guides at the entrance ensure perfect alignment. The machine is closed until the gap between forming blocks corresponds to the particular thickness of the plastic strip being formed.The forming prongs have now formed the strap retaining ridges on to the top of the plastic angle, the plastic now stays clamped between the forming blocks while it travels the length of the machine, allowing the plastic to set hard.

The hard plastic angle now passes on to a croppng machine where first a double sided strip of adhesive tape is automatically applied onto the underside of the plastic angle. The angle is now cut into exact 38mm lengths with the strap retaining ridges equispaced from each end. Variable lengths of edge protectors can be produced by this method, made up in multiples of 38mm. Therefore if cropping machine is set to cut the edge protectors 76mm long, which is equivalent to two forming blocks side by side, we now have a choice regarding the position's of the ridges due to the fact that the forming prongs are detachable. We can either remove the two inner forming prongs leaving the ridges at each end of the extra long edge protector, or remove the outer forming prongs leaving the inner ridges. Many variations of the product can be achieved in this manner.

2. A process as claimed in claim 1 wherein the forming blocks are shorter or longer in length than 38mm, with forming prongs fitted.

3. A process as claimed in claim 1 wherein the thermoplastic material is polyvinyl chloride, low and high density polythene and polypropylene.

4. Apparatus as claimed in any claims 1-3 wherein the extruded thermoplastic strip can vary in width and thickness according to particular size of edge protector being formed.

5. Apparatus as claimed in any claims 1-4 comprising an extruder having a slit die extruding a substantialy flat strip.

6. Apparatus forthe carrying out of the process claimed in claim 1 comprising an thermoforming machine having male and female forming blocks.

7. Apparatus for the carrying out of the process claimed in claims 1 and 6 comprising of male forming blocks fitted with forming prongs.

8. Apparatus for the carrying out of the process claimed in claims 1.2.6.7 wherein the male and female blocks are made of material which is a good conductor of heat.

9. Apparatus for the carrying out of the process claimed in claims 1.2.6.7.8 wherein the male and female forming blocks are temperature controlled.

10. Apparatus for the carrying out of the process claimed in claims 1.2.6.7.8. wherein the male and female forming blocks are not temperature controlled.

11. A process for the production of thermoformed plastic angle, with thermoformed ridges pressed into it, as hereinbefore described and according to any one of claims 1-10 and as illustrated with reference to any of the drawings accompanying the provisional specification.

12. Apparatus for the production ofthermoformed plastic angle with thermoformed ridges pressed into it, as hereinbefore described and as illustrated with reference to any of the drawings accompanying the provisional specification.