NZ203272A - Bending plastics pipe - Google Patents

Description

203272 Priority Date(s): /£.

Complete Specification Filed: .AW.P,'.^ Cfas6: £7?"?. ., PuWica*ion Date: (t ?. !???.

P.O. Journal, No: .

No.: Date: NEW ZEALAND PATENTS ACT, ]953 T^Nr^ 14FEBI983 I * '•! A / COMPLETE SPECIFICATION PIPE SHAPING'PROCESS AND APPARATUS FOR USE IN PROCESS I/% STEWART KENNETH MCKAY, an Australian citizen of National Park Road, Canungra, Queensland, Australia 4275, Australia hereby declare the invention for which I / pray that a patent may be granted to me/^, and the method by which it is to be performed, to be particularly described in and by the following statement:- 203272.

THIS INVENTION relates to a process for shaping a pipe member formed from plastics material, Hitherto bending or shaping of pipe and in particular bending of pipe formed from plastics material such as polyvinyl choloride (PVC) has not been entirely successful in carrying out the bending process without kinks or other deformations occurring in the tube. Often opposed parts of the continuous side wall of the tube (which was of circular cross section) were flattened and the bent portions of the tube usually did not have a uniform cross section. Usually such fi">t 10 deformities were unwelcome in furniture formed from the bent tube as 'i" they detracted from the appearance and aesthetic appeal of such furniture. 1 It is therefore an object of the invention to provide a pipe shaping process which alleviates the abovementioned difficulties Cy" -1-5 associated with the prior art.

The pipe bending process of the invent]on.includes the following steps: (i) heating a flexible insert to a temperature in the region of the softening point of the pipe member; (ii) inserting said flexible insert into an internal bore of said pipe member; (iii) applying to each free end of the pipe member means to maintain dimensional stability during a subsequent heating process; (iv) heating the resulting assembly to a temperature in ^ 25 the region of the softening point of the pipe member rendering said pipe member deformable; and (v) arranging said softened assembly in a shaping device ^ "SNAYiKvo to shape the pipe member to a predetermined shape.- Preferably the pipe member is of uniform cross section and 30 is circular. It is preferred that the pipe member is resistant to UV light and has a high gloss white finish thereby being able to maintain its colour and thus not be susceptible to fading or powdering. The pipe member should also maintain its colour during the heating and shaping steps.

Suitably the pipe member has a substantially constant wall thickness and also a substantially constant outside diameter. It is also desirable that the pipe member be inpact resistant and thus withstand an impact test of 66 pounds weight dropped through, one foot.

In step (i) it is also preferred that the insert be suitably made 'n from natural rubber, artificial rubber or other suitably flexible or 203272. resilient material which may be inserted into the pipe member.

Preferably the flexible insert is heated, prior to its insertion in the pipe member, to a temperature between 340 and 450°F and more preferably 370 and 420°F.

Suitably after insertion of the flexible insert within the pipe member preferably with the assistance of talcum powder there are provided suitable end sleeves or caps which may be formed from rubber hose or other suitable flexible or resilient material of slightly larger diameter than the outside diameter of the pipe member.

Preferably the end caps or sleeves are wrapped in cloth and soaked with water.

Preferably the flexible insert is longer than its mating pipe member and thus has end portions which project from each end of the pipe member. The above described end caps or sleeves are suitably pushed over the outwardly projecting or free ends of the flexible insert until they bear against an adjacent end of the pipe member.

The purpose of the end caps of "wet ends" is to keep the ends of the pfpe member cool and.thus inhibit thermal stress relief in the region of the pipe member accompanied by diametrical shrinkage during the heating process. This is a desirable feature in that when the shaped pipe member is Being fitted with preformed standard elbow joints, T-joints or other suitable joint members for use in the manufacture of furniture for example there would Be relatively sloppy or loose fit if the ends of the pipe member were reduced in diameter after the heating step.

The heating means used for the heating step may Be of any suitable type and suitably incorporates a heating oven which is preferably fully insulated. The oven may Be of any suitable size and in one form may measure approximately 1 m diameter x 3 m long using three standard infra red strip heaters. Thus the heating ovens are suitably tubular or of round cross section.

A tray which is suitably corrugated and formed from galvanized iron and centrally located in the oven may run the full length thereof "and be utilized to support the pipe members to be shaped. Preferably the tray contains a plurality of slots or apertures to enable the heat to readily pass through the tray. The purpose of the corrugations is to inhibit the pipe members from sliding or moving on the tray and also to inhibit the production of "flat spots" occurring along the^0 * length of the pipe members during the heating step. ff (r-8MAYl%6 . - r-A-'1 i.~ ... . r 203272 The pipe members with end caps attached are placed in the oven and heated until the pipe members are pliable. A suitable temperature is between 340 and 450°F and more preferably the temperature is between 370 and 420°F. It will be noted that the flexible inserts are also 5 suitably heated to a similar range of temperatures before being placed within an associated pipe member. This enables the pipe members while being heated externally by the oven to be also heated internally by the flexible inserts. ' After the pipe members have been heated they are withdrawn from 10 the oven and then placed in a suitable shaping device so as to be shaped or formed into the desired sriape.

Suitably the shaping device includes a shaping passage or mould passage which may be of channel shape or alternatively may be of round cross section. If desired the shaping device may comprise opposed 15 shaping components or "half-moulds" wherein one component may be moved out of engagement with the other component to allow placement of the heated pipe member within one part or base portion of the shaping passage contained in the said other component. The said one component may comprise another part or top portion of the shaping passage which engages 20 with the base portion when both components engage with each other.

More preferably however the shaping devide includes a base component containing a shaping passage of channel shaped cross section. There also may be provided a plurality of clamps associated with the base component so as to maintain the pipe member in the shape orientat-25 ion.

Various shapes of pipe member may be formed such as a U shape, W shape, V shape, or any other suitable shape.

In a preferred form the base component has a U shaped shaping passage of channel shaped cross section and has a pair of top clamps 30 which engage with each opposed arm of the U.

Reference may now be made to a preferred embodiment of the invention as shown in the accompanying drawings wherein: v FIG 1 is a perspective view of a shaping device constructed in accordance with the invention; 4. 203272 FIG 2 is a perspective view of the shaping device of FIG 1 from a different angle; FIG 3 is a perspective view of an alternative shaping device constructed in accordance with the invention; FIG 4 is a schematic view of the heating step of the method of the invention; FIG 5 is a part sectional of a pipe member containing a flexible insert and having attached thereto a "wet end"; FIG 6 is a schematic view of the pipe member after the heating step.

In the drawings there is shown in FIGS 1-2 a shaping device 10 having base supports 11 and frame 12. Frame 12 includes a U shaped shaping passage 13 having offset end portions 13A. Frame 12 also has attached thereto a pair of opposed top clamps 14 having shaping passages 14A which register with shaping passage 13 in the closed position and handles 14B. There is also shown a pair of opposed base clamps 15 each having lever arm 16, handle 17, pivot point 18 wherein lever arm 16 is attached to frame 12 and retaining block 19 having shaping passage 19A. There is also shown lever arm support block 20. Top clamps 14 are pivotally attached to frame 12 by hinges 21. Block 20 is pivotally attached to frame 12 by hinge 22.

FIG 1 shows the shaping device 10 in the fully closed position and FIG 2 shows the shaping device 10 with one clamp 14 in a partially open position as well as one clamp 15 being in a partially open position.

In FIG 3 there is shown another shaping device 10A of the same general construction as shaping device 10 but incorporating a rear clamp 23 with shaping passage 24 and handle 25 as well as top clamps 14. . ° \\ 1 1 FEB 1986 203272 . There is also shown base clamps 26 which open outwardly from frame 12A as shown and are attached thereto by hinges 22A. In contrast clamps 15 of FIGS 1t2 open inwardly or in the opposite direction to clamps 26.

In the FIGS 1-3 embodiments the rubber insert is retained in the pipe member after it has been moulded or shaped to the desired shape by shaping devices 10 and 10A. ^ In shaping devices 10 and 10A the (**) pipe member is placed in lower shaping passages 13 and 13A and easily bent to the desired shape after all clamps have been fully opened. The clamps are then closed and the pipe member after cooling is removed by opening of the relevant clamps.

The rubber insert in shaping devices 10 and 10A may be removed while the pipe member has been cooled and is retained in the shaping device. ) Suitably pipe members which are shaped in the process of the invention are suitably such as to have an ability to be bent wherein the 4nternal radius of the bend portion (i.e. the radius of the inside bend) of the pipe member is at least equal to the diameter of the tube without the pipe member cracking or being deformed. This is commonly known in the art as a "ID" bend and is a fairly acute bend. Normally however the bend is of more shallow nature so that the internal radius of the bent portion is greater than the diameter of the pipe member. 6. '' 203272 When the heated pipe members are removed from the oven usually the "wet ends" are removed before the heated pipe members are shaped 1n the shaping device. The heated pipe member may be manually placed in the shaping passages of the shaping device and after clamping sets 5 usually after a few minutes. Once the pipe member is hard the rubber inserts in the case of FIGS 1-3 may be removed for more rapid cooling of the pipe members.

FIG 4 shows a pipe jnember 40 having flexible insert 42 and "wet ends" 41 about to be inserted in a heating oven 37 having corrugated 10 tray 38 and support legs 39.

FIG 5 shows flexible insert 42 within internal bore 43 of pipe jnember 40 and "wet end" cooling the adjacent end of pipe member 40.

FIG 6 shows how malleable or pliable pipe member 40 appears after being heated in oven 37.

Preferably the shaping devices are constructed mainly from timber and finished in a heat resistant resin which encloses suitably 50% of the pipe member when located within the shaping device. In some cases where a sharp bend is required the tube is clamped as described above. Preferably the shaping passages in the clamps are adapted to 20 contain 50% of the pipe member.

There is usually a clamp on each side of a sharp bend to clamp the pipe member very tightly around the bend. The clamps are usually retained in the closed position until the pipe member is cool enough to be removed from the shaping device.

Preferably the pipe Member which 1s treated by the shaping process of the invention is made from PVC and contains at least 3.0% and more suitably at least 4.5% of titanium dioxide. Most preferably the pipe member contains at least 5.0 - 5.3% of titanium dioxide.

It will also be appreciated that the process of the invention is also applicable to pipe members made from other plastics materials such as ABS, polycarbonates and acrylic plastics generally.

Claims (11)

203272 WHAT^ VVZ CLAIM IS: ^

1. A process for shaping a, pipe member formed from plastics material including th.e steps of: (i) heating a flexible insert to a temperature in the region of the softening point of the pipe member; (ii) inserting said flexible insert into an internal bore of said pipe member; (iii) applying to each free end of the pipe member means to maintain dimensional stability during a subsequent heating process; Civ) heating the resulting assembly to a temperature in the region of the softening point of the pipe member rendering said pipe member deformable; and (v) arranging said softened assembly in a shaping device to shape the pipe member to a predetermined shape.

2. A process as claimed in claim 1 wherein the pipe member is heated to a temperature of between 340° arid 450°F.

3. A process as claimed in claim 2 wherein the pipe member is heated to a temperature of between 370° and 420°F,

4. A process as claimed in any preceding claim wherein in step (iii) end sleeves formed from resilient material of slightly larger diameter than the pipe member are placed on outwardly projecting ends of the flexible insert adjacent to or bearing against a respective end of the pipe member to cool same after heating.

5. A process as claimed in any preceding claim wherein the flexible insert is heated prior to insertion in the pipe member to a temperature of between 340° and 450°F.

6. A process as claimed in claim 5 wherein the flexible insert is heated to a temperature of between 370° and 420°F.

7. A process as claimed in any preceding claim wherein the shaping device is provided with clamps so as to maintain the heated pipe member in the desired shape orientation.

8. A process as claimed in claim 7 wherein a pair of clamps are located on each side of a bend in the shaping device. 8. 203275

9. A process as claimed in claim 1 wherein the pipe member contains from 3,0 to 5,3% of titanium dioxide,

10. A process as claimed in claim 1 and substantially as herein described with reference to any enibodiment shown in the accompanying drawings.

11. A pipe member shaped by the process of any one of the preceding claims. DATED THIS DAY OF V^C p..- ri 1FEBi986£jj