GB2284570A

GB2284570A - Improvements in and relating to the bending of elongated plastics sections

Info

Publication number: GB2284570A
Application number: GB9413154A
Authority: GB
Inventors: Alan Cunningham
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-12-06
Filing date: 1994-06-30
Publication date: 1995-06-14
Anticipated expiration: 2014-06-30
Also published as: GB9413154D0; GB2284570B

Abstract

Apparatus for use in bending pre-heated elongated plastics members 20 to a predetermined arcuate shape comprising a support table 22, a former 28 and a plurality of mounting means 26 to which said former 28 engages and wherein the position of each mounting means 26 is adjustable such that the former 28 adopts the desired arcuate shape. In a first aspect of the invention the former 28 co-operates with the mounting means 26 by sliding engagement (via locating pins 62 having cylindrical heads 66, 68 riding in T-shaped slots 60, 35 formed in former 28 and mounting means 26 respectively) and in a second aspect the former 28 is movable perpendicularly to the plane of the table 22. The invention finds particular application in the bending of uPVC members for windows and doors. <IMAGE>

Description

Title: Improvements in and relating to the bending of elongated plastics sections DESCRIPTION This invention relates to the bending of elongated plastics sections and, in particular, to the bending of uPVC sections to a predetermined arcuate shape.

The use of plastics as a building material is now common especially in the form of window and door frames.

It is often required to bend an elongate plastics member to an arcuate shape in order to produce, for example, a decorative arch.

A cross-section of a typical plastics member is shown in Figure 1 of the accompanying drawings and is substantially hollow having compartments 10, 12, 14 and 16. The typical plastics member is generally L-shaped having a generally vertical portion 18 denoted by the dotted outline and a horizontal portion 20. A lip 15 projects from the vertical portion and therein defined between the vertical portion, lip and a part of the horizonal portion is a recess 17.

A known method of bending an elongated plastics member is to heat the member until it becomes soft and to bend the member around a former. The former has an outer shape which corresponds with what will be an inner face of the member to make contact with same.

However, one problem experienced with this method is that the member is liable to ripple or buckle as it is being bent around the former due to the fact that the member is substantially hollow.

In order to overcome the above problem it has been proposed (as described in EP 0041154 of Maschinen Witte KG) to provide a pair of spaced apart concentric mould parts. The mould parts have complimentary faces which conform to opposite faces of the plastics member to be bent, ie. what will be inner and outer faces. The section is drawn through a channel between said parts and the mould parts support the member as it is being bent. Although this method alleviates the above problem it is far more complicated since it requires closely conforming mould parts and a mechanism for drawing the member through the channel.

The two above-mentioned methods involve the securing of either a former or concentric mould parts to mounting blocks whose positions are adjustable such that when the former or concentric mould parts is secured thereto it will adopt the desired arcuate shape. In consequence, a further problem experienced is the time consuming operation of securing either the former or concentric mould parts to the mounting blocks which usually involves the screwing of each block to the former or concentric mould parts as the case may be.

A first aim of the present invention is to provide an apparatus for bending elongate plastics members which reduces the time consuming task of securing either of a former or concentric mould parts to mounting blocks.

A second aim of the present invention is to provide an apparatus for bending elongated plastics members which reduces the above-mentioned problem associated with the sections rippling or buckling.

A further aim of the present invention is to provide a method of bending elongated plastics members.

A former is a member around which a heated plastics member is bent and a mould part forms one of a pair of concentric mould parts between which a heated plastics member is positioned. Hereinafter, the term "former" will be understood to include the term "mould parts".

In accordance with a first aspect of the present invention there is provided apparatus for use in bending pre-heated elongated plastics members to a predetermined arcuate shape comprising a support table, a former and at least one mounting means with which said former cooperates by sliding engagement.

In a preferred embodiment there are provided a plurality of mounting means to which said former is secured.

The position of each mounting means is preferably adjustable such that the former adopts a desired arcuate shape when cooperating therewith.

The sliding engagement between the former and the mounting means may be in a plane parallel to the plane of the support table.

The former and mounting means may be provided with cooperating slot and protrusion in order to provide said sliding engagement. Preferably, said former is elongate and preferably has a longitudinal extending slot in an inside face thereof. The slot preferably extends the entire length of the former.

Each mounting means may have a protrusion which engages with said slot formed in the former. The protrusion may be formed integrally with said mounting means. The protrusions may comprise a body and a head formed at the end thereof and said head may be cylindrical.

In accordance with a second aspect of the present invention there is provided an apparatus for use in bending pre-heated elongated plastics members to a predetermined arcuate shape comprising a support table, a former around which said plastics sections are bent and means for securing the former in a desired arcuate shape and wherein said former is adjustably movable perpendicularly to the plane of said table.

Advantageously, perpendicular movement allows a part of a plastics member to lie between a bottom surface of the former and said table.

The former may having an outer surface which corresponds to, at least in part, the shape of a side of the plastics section to be bent. However it is preferred for the former to have a substantially flat outer surface.

It is preferred that said means comprises a plurality of mounting means with which the former cooperates.

The position of each mounting means is preferably adjustable such that the former adopts a desired arcuate shape when secured thereto.

The perpendicular movement of the former to the plane of said table may be provided by sliding engagement between said former and mounting means.

The former and mounting means may be provided with cooperating slot and protrusion in order to provide said sliding engagement. Preferably, each mounting means has a slot aligned perpendicularly with respect to the plane of the table and formed in a front face thereof. The slot may extend the full height of the front face but, more preferably, extends from a top edge of the front face to a position midway down the face of the mounting means.

The former may comprise a plurality of said protrusions spaced apart and extending from an inner face thereof for engagement with a respective mounting means.

The protrusions may comprise a body and a head formed at the end thereof and said head may be cylindrical.

In a preferred embodiment of the invention, said protrusions are not integral with said former but are separate and distinct items. The protrusions preferably comprise a body having a head formed at each end. It is preferred that said former comprises a substantially horizontal slot formed in an inside face thereof and said slot may be adapted to receive a head and, more preferably, holds such head captive therein.

Preferably, said protrusions permit substantially horizontal sliding movement of the former with respect to the mounting means. It is preferred that said slot is T-shaped in cross-section and said protrusions are Tshaped. The protrusions may be a frictional fit with said slots.

In accordance with a further aspect of the present invention there is provided a method of bending an elongated plastics member having one or more elongate hollow compartments to a predetermined arcuate shape comprising the steps of:1) heating the plastics member to a predetermined temperature; 2) inserting a support into one or more of said elongate compartments; and 3) bending said plastics member around a former secured in a desired arcuate shape.

Preferably, a support is inserted into each hollow compartment.

The former may be perpendicularly movable relative to the plane of a support table and said method may further comprise the step of adjusting the perpendicular height of the former above the support table such that a portion of the plastics member may be inserted between a bottom surface of the former and the support table.

The former may have an outer surface which conforms, at least in part, to the shape of a side of the plastics member to be bent, but preferably, the outer surface of the former is substantially flat.

The method may comprise the additional step of interposing a support between the plastics member and the former thereby resulting in a bending force being exerted via the support onto the member abutting the support.

The plastics member may be heated to the required temperature by immersion in oil. Another aspect of the invention preheats the plastic member using radiant heat, especially using infrared heaters.

The invention will now be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view through a uPVC member; Figure 2 is a plan view of an apparatus for bending preheated elongated plastics members according to the present invention; Figures 3 and 4 are respective plan and side views of a support block; Figure 5 is a side view of a support block and clamp arrangement; Figure 6 is a side view of the support block with a former connected thereto by a locating pin; Figure 7 is a front view of a former; Figure 8 is an end view of the former with a locating pin fitted; Figure 9 is an enlarged side view of the locating pin; Figure 10 is an end view of the plastics member in its bent position.

Referring to the drawings and in the first instance to Figure 2, an apparatus for bending an elongate plastics member is indicated by numeral 21.

The apparatus comprises a support table 22 having a plurality of slots 24 extending radially, a plurality of support blocks 26 and a former 28.

Figures 3 and 4 illustrate the support blocks 26.

Each is basically rectangular in shape and has a front face 30, top face 32 and a bottom face 34. Extending from the top face 32 to a position midway towards the bottom face is a T-shaped slot 35 which is open to the front face. A bore 36 is formed through the block.

Referring to Figure 5, a clamping mechanism is indicated by numeral 38 and comprises a lever 40 having a lever cam surface 42, a rod 44 which at one end is pivotally connected to the lever and atthe other end carries a spring biased clamp plate 46. The shank of rod 44 passes through the bore 36 and a through a slot 24 in the support table 23. With the lever in the position shown, the clamp plate 46 is held against the bottom surface of the table 22 by the spring such that the support block is restricted from complete free movement although it can be moved along the length of the slot 24. Movement of the lever in the direction of arrow A will result in the rod being lifted upwards due to the nature of the cam and hence the clamp plate 46 will exert a greater clamping force on the bottom surface of the table surrounding the edges of the slot.

As a result, the support block is secured in a position along the length of the slot and can simply be released by movement of the lever back to the position indicated.

The former 28 is in the shape of a rectangular strip and has a smooth outer face 48, an inner face 50, top and bottom faces 52, 54 and end faces 56, 58.

Formed with in the inner face 50 is a longitudinal Tshaped slot 60 which extends between end faces 56 and 58. The cross-sectional dimensions of the slot are similar to those of slot 35. The former is made from a flexible plastics material and to improve the flexibility of the former a plurality of spaced apart vertical slots 61 are formed in the inner face extending from the top to bottom face.

A locating pin is illustrated in Figure 9 and is indicated by numeral 62. The pin comprises a shaft 64 with cylindrical heads 66, 68 formed at respective ends.

In order to set the apparatus up so that a plastics member can be bent to the desired arcuate shape it is necessary to position the former. Firstly, the clamping mechanisms for the support blocks 26 are released and the blocks moved along their respective slots until a predetermined position is reached which corresponds to the radius of the required arcuate shape.

The blocks are then clamped into position by movement of levers 40 which forces the corresponding clamp plates 46 against the underside of the slot and hence the blocks are clamped into position.

A plurality of locating pins corresponding to the number of support blocks are inserted, from one end of the former, into the T-shaped slot 60 and positioned along the length of the slot such-that they are spaced apart, the spacing corresponding to the distance of separation between adjacent support blocks. The head 66 of each locking pin is held captive within the slot.

The former is connected to the support blocks by the locating pins wherein the heads 68 are inserted into the T-slots 34 from the top surfaces 32 of the support blocks. The head 68 of each locking pin is held captive within the T-shaped slot of corresponding support blocks.

In an alternative embodoment, the locating pins are firstly positioned in slots 34 and then the former is slotted onto the pins such that the former is slidingly engaged.

Said head 68 is a frictional fit within the Tslot and hence although the head can be forced vertically up and down the slot, once positioned in the slot said frictional forces holds the head and hence the former in position. In this manner, the height of the former above the support table can be adjusted.

The method of bending a plastics member will now be described with initially the apparatus set up as described above such that the former is set to the desired arcuate shape.

A plastics member as illustrated in Figure 1 and described hereinbefore is heated by an infra-red source (not shown) until the section has reached a predetermined temperature sufficient for bending purposes.

As can be seen, the member comprises four compartments 10, 12, 14 and 16. Rectangular support strips 70 which are heated to the same temperature as the section inserted into the compartments so as to add support in the member.

The height of the former above the support table is adjusted so as to allow the horizontal portion 20 of the member to slide between the support table 22 and the bottom of the former 54 as the member is being bent. By allowing said horizontal portion to be beneath the former there is no need for the former to have a complicated outer surface to correspond with the shape of the whole side of the plastics member to be bent. In this embodiment the outer surface 48 of the former is flat and in order to increase the surface area of the member which has a bending force exerted onto it by the former, a support strip 72 is positioned in the recess 17 and the former.

The heated member with support strips 70 is forced by hand or mechanical means around the former.

Support strip 72 being positioned between the former and member thereby transmitting the bending force to the member. As the member is being bent around the former, pressure is exerted onto the top of the former so as to clamp the portion of the member held between the lower end of the former and the table so as to prevent rippling and buckling of the member. Once the member has been bent into the shape of the former, the member is allowed to cool and hence sets to the arcuate shape required.

The support strips 70 prevent the section from distorting whilst it is being bent around the former and during cooling.

In the above embodiment of the invention, the outer surface of the former is flat and hence there is no requirement to have a stock of formers each having an outer surface which conforms to the shape of the section to be bent.

Claims

1. An apparatus for use in bending pre-heated elongated plastics members to a predetermined arcuate shape comprising a support table, a former and at least one mounting means with which said former cooperates by sliding engagement.

2. An apparatus for use in bending pre-heated elongated plastics members to a predetermined arcuate shape comprising a support table, a former around which said plastics sections are bent and means for securing the former in a desired arcuate shape and wherein said former is adjustably movable perpendicularly to the plane of said table.

3. Apparatus according to claim 1 or 2, wherein there is provided a plurality of mounting means with which said former slidably engages.

4. Apparatus as claimed in claim 1 or 3, wherein the position of the mounting means is adjustable such that the former adopts a desired arcuate shape when cooperating therewith.

5. Apparatus as claimed in claims 1, 3 or 4, wherein said sliding engagement between the former and the mounting means is in a plane parallel to the plane of the support table.

6. Apparatus as claimed in claims 1, 3, 4 or 5, wherein the former and mounting means is provided with cooperating slot and protrusion means in order to provide said sliding engagement.

7. Apparatus according to any one of claims 1 to 6, wherein said former is elongate and has a longitudinal extending slot in an inside face thereof.

8. Apparatus as claimed in claim 7, wherein the slot extends the entire length of the former.

9. Apparatus as claimed in claims 7 or 8, wherein each mounting means has a protrusion which engages with said slot formed in the former.

10. Apparatus according to any one of claims 6, 7, 8 or 9, wherein the protrusion is formed integrally with said mounting means.

11. Apparatus as claimed in any one of claims 6 to 10, wherein the protrusion comprises a body and a head formed at the end thereof.

12. Apparatus as claimed in claim 11, wherein said head is cylindrical.

13. Apparatus as claimed in any one of the preceding claims, wherein said former has an outer surface which corresponds to, at least in part, the shape of a side of the plastics section to be bent.

14. Apparatus according to any one of claims 1 to 12, wherein the former has a substantially flat outer surface.

15. Apparatus according to claim 2, or any one of claims 3 to 14 when appendant to claim 2 wherein said perpendicular movement of the former to the plane of said table is provided by sliding engagement between said former and said mounting means.

16. Apparatus as claimed in claim 15, wherein the former and mounting means is provided with cooperating slot and protrusion means in order to provide said sliding engagement enabling said perpendicular movement.

17. Apparatus as claimed in claim 16 wherein each mounting means has a slot aligned perpendicularly with respect to the plane of the table.

18. Apparatus according to claim 16 or 17, wherein said slot is formed in a front face of said mounting means.

19. Apparatus according to claim 18, wherein the slot extends the full height of the front face.

20. Apparatus according to claim 18, wherein said slot extends from a top edge of the front face to a position midway down the face of the mounting means.

21. Apparatus as claimed in any one of claims 16, 17, 18, 19 or 20, wherein the former comprises a plurality of said protrusions spaced apart and extending from an inner face thereof for engagement with a respective mounting means.

22. Apparatus as claimed in any one of claims 16 to 21, wherein each protrusion comprises a body and a head formed at the end thereof.

23. Apparatus according to claim 22, wherein said head is cylindrical.

24. Apparatus as claimed in any one of claims 16 to 23, wherein said protrusions are not integral with said former but are separate and distinct items.

25. Apparatus according to claim 24, wherein each protrusion comprises a body having a head formed at each end.

26. Apparatus as claimed in any one of claims 16 to 25, wherein said slot is T-shaped in cross-section and said protrusions are T-shaped.

27. Apparatus according to any one of claims 16 to 26, wherein the protrusions are a frictional fit within said slots.

28. A method of bending an elongated plastics member having one or more elongate hollow compartments to a predetermined arcuate shape comprising the steps of:1) heating the plastics member to a predetermined temperature; 2) inserting a support into one or more of said elongate compartments; and 3) bending said plastics member around a former secured in a desired arcuate shape.

29. A method according to claim 28, wherein a support is inserted into each hollow compartment.

30. A method according to any one of claims 28 or 29 wherein the former is perpendicularly movable relative to the plane of a support table.

31. Apparatus as claimed in claim 30, wherein said method further comprises the step of adjusting the perpendicular height of the former above the support table such that a portion of the plastics member is inserted between a bottom surface of the former and the support table.

32. A method as claimed in any one of claims 28 to 31, wherein the former has an outer surface which conforms, at least in part, to the shape of a side of the plastics member to be bent.

33. A method according to any one of claims 28 to 31, wherein the outer surface of the former is substantially flat.

34. A method as claimed in any one of claims 28 to 33, wherein said method further comprises the step of interposing a support between the plastics member and the former thereby resulting in a bending force being exerted via the support onto the member abutting the support.

35. A method according to any one of claims 28 to 34, wherein the plastics member is heated to the required temperature by immersion in oil.

36. A method as claimed in any one of claims 28 to 34, wherein the plastics member is heated using radiant heat.

37. A method as claimed in claim 36, wherein said radiant heat is provided by infrared heaters.

38. An apparatus for use in bending pre-heated elongated plastics members to a predetermined arcuate shape substantially as hereinbefore described with reference to and as illustrated in the accompaying drawings.

39. A method of bending an elongated plastics member having one or more elongate hollow compartments substantially as hereinbefore described with reference to the accompanying drawings.