CA2144719A1

CA2144719A1 - Extrusion method and apparatus therefor

Info

Publication number: CA2144719A1
Application number: CA002144719A
Authority: CA
Inventors: Vittorio De Zen
Original assignee: Royal Group Inc Canada
Current assignee: Westlake Canada Inc
Priority date: 1995-03-15
Filing date: 1995-03-15
Publication date: 1996-09-16
Also published as: WO1996029186A2; AU4934296A; WO1996029186A3

Abstract

A method of simultaneously extruding at least two thermoplastic profiles utilizing a single extruder outputting a flow of heated thermoplastic material comprising dividing the output flow from the extruder into at least two streams, delivering each of said streams through a profile forming die to convert the stream to a profiled stream, individually pulling each profiled stream emerging from its profile forming die through a calibrating unit for that profile, and adjusting the speed of pull of each profiled stream so that the take away of the profiled stream from its respective profile forming die matches the rate at which it emerges therefrom. The invention also includes apparatus for carrying out the method.

Description

-- 1 21~4719 EXTRUSION METHOD AND APPARATUS THEREFOR

FIELD OF THE INVENTION

This invention relates to an extrusion method and apparatus therefor.

BACKGROUND OF THE INVENTION

Extrusion lines for producing extruded thermoplastic products formed by forcing heated thermoplastic material through a die and then calibrating same to produce a product stream having a desired cross sectional shape and size or profile require the employment of equipment requiring a very substantial outlay of capital.
Each extrusion line requires the use of an extruding machine or extruder to force the heated plastic through the requisite die, a series of vacuum operated profile sizers or calibrators for finally forming and cooling the product stream so that it has precisely the profile desired, a puller mech~ni~m to pull the product stream through the calibrators, a cutoff or saw mech~ni~m to cut off a~propliate lengths of the product, and a receiving table to receive the cut product lengths.

Each such extruder line occupies a substantial area of plant floor

2 5 space and requires its own utilities and operator.

Extrusion manufactures usually extrude products having a range of sizes from small profile products having a small volume of material per foot, to large profile products having a substantial volume of material per foot.
The smaller profile products are conventionally produced on extrusion lines having smaller capacity extruders while the large profile products require extrusion lines with extruders of much higher capacity.

21~4719 The smaller capacity extruders which having a somewhat lower cost than the high capacity extruders are not capable of delivering a sufficientvolume of heated material at a sufficient pressure to render them practical to produce the large profiles. On the other hand, it is not practical to take 5 advantage of the capacity of the large capacity extruders to produce the ~m~ller profiles since if they were operated at capacity they would have to deliver a product stream at such high velocity that it would be impractical to properly calibrate same and obtain a precision profile.

As a result, at present, the production of small and large extrusion profiles has required a proliferation of extrusion lines occupying a large plantfloor area with each line requiring its own operator and service utilities such as electrical power and cooling water lines.

BREF DESCRIPTION OF THE INVENTION

The present invention resides in a method and a~p~atus whereby a high capacity extruder can be operated efficiently to not only produce 2 o precision small profiles as well as precision large profiles but will produce such small profiles at an output rate substantially matching the output of at least two separate small capacity extruder lines thereby reducing or elimin~ting the need of multiple extrusion lines to provide important cost savings in plant space and utility and manpower costs.
More particularly, the invention resides in dividing the output flow of an extruder into separate stream flows, delivering each stream through a profile forming die to produce a profiled stream ,and individually pulling each profiled stream through its associated calibrators at a speed so that the 30 profiled stream emerging or exiting from its profile forming die is pulled away thererlolll at the same speed with which it emerges.

3 21~4719 BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a perspective view of the front portion of an extrusion line embodying the invention;

Figure 2 is a perspective view of the end portion of the extrusion line of Figure l;

Figure 3 is a broken away perspective view illustrating a flow 10 divider assembly attached to the output of the extruder;

Figure 4 is a horizontal cross-sectional view of the flow divider of Figure 3 and showing it feeding separate die assemblies;

Figure 5 is a front elevational view of typical profile forming dies for forming typical profiled products which can be extruded simlllt~neously according to the invention;

Figure 6 a broken away perspective view illustrating the profiled 2 o product streams being pulled through the system by independent pullers;

Figure 7 is a schematic perspective view illustrating the independent drive of the separate pullers;

2 5 Figure 8 is a broken away perspective view illustrating the independent saws for cutting off the desired lengths of the separate simultaneously produced profiled product streams;

Figure 9 is a perspective view of an alternative form of flow 3 o divider having provision for selectively closing off one or other of the divergent branch leg portions of the flow dividing Y passage;

4 21q4719 Figure 10 is a diagr~mm~tic horizontal cross sectional view showing the shutter member in its middle position with both divergent branches of the Y passage open;

Figure 11 is a view similar to Figure 10 but showing the shutter bar moved to block off the right hand branch of the Y passage while the left hand branch is fully open;

Figure 12 is a view similar to Figure 11 but showing the shutter bar moved to block off the left hand branch of the Y passage while the right hand branch is fully open;

Figure 13 is a broken away perspective view of the use of the parallel pullers pulling a large profiled product stream through the system when the flow divider is removed and the extruder feeds a single die of a large proffle requiring the extruder to be operated at full capacity.

Extruders for extruding heated thermoplastic material through a 2 o profile forming die to produce a thermoplastic product stream having a predetermined cross sectional configuration or profile are available with different capacities. The capacity of an extruder in measured in terms of the quantity of thermoplastic material it can deliver at extrusion pressures per unit of time.
Extruders normally, in addition to heating the thermoplastic material to an appr~liate temperature normally of the order of 170 to 180 C for flowing through the extrusion die, employ a feed screw to deliver the heated material to the die under extruding pressure and at a feed rate 3 o dependent upon the speed of rotation of the feed screw operated by a variable speed drive.

For an example, extruders capable of delivering from about 200 to 300 kilogr~ms or from about S00 to 700 pounds of heated thermoplastic -

- 5 - 21 44 71 9 material per hour and at an extrusion pressure of the order of about 3,000 to S,000 pounds per square inch would be considered in the higher capacity extruder range for profiles.

If an extruder with a capacity of 600 pounds per hour were used at capacity to produce a proffled product having a weight of one pound per foot, then the product would be produced in a stream flow of lO feet per minute.
A proffled product having a weight of one-half pound per foot would be produced at a stream flow of 20 feet per minute.

The product stream exiting from the proffle die is relatively soft and does not have the proffle precision required in the ffnal product being usually about l to l l/2% bigger than the ffnal proffle. This rough profile stream then is required to be pulled through sizers or calibrators having the applopliate internal conffgurations corresponding to the profile die where the stream is subjected to vacuum to pull same forcefully against the calibrator's walls while at the same time it is subject to the cooling effect of water being circulated within the calibrators so that the product exiting thererloll~ has a precise and accurate profile.
If the product stream from the forming die exits or emerges too fast because the extruder is operating at or near capacity, the speed at which the product stream must be pulled through the calibrators will be too high to provide the requisite cooling and sizing so that the product stream exiting the calibrators will not have the requisite accuracy. It is then necessary to slow down the feed of the extruder so that it is operated at a reduced capacity and its value as a high capacity machine is lost.

In attempting to solve the problem and enable the extruder to be 3 0 used at or near full capacity for extrusion products with smaller proffles, the output flow of the extruder was split into separate equal flow passages and the material in these passages forced through forming dies of the same configuration to produce two product streams of the same profile. However, when these two streams were pulled through their calibrators, the products

- 6 - 2144 719 formed were unacceptable and did not have the requisite profile precision or accuracy. Allem~ts to solve the problem by adjusting the relative heating of the profile forming dies to alter the flow characteristics thereof were unsuccessful.

It was finally discovered however that product streams with precisely accurate profiles could be sim~llt~neously produced from one extruder by pulling each product stream individually with its own puller whose speed could be precisely controlled so that each separate product 0 stream exiting each die could be pulled through its associated calibrators at precisely the right speed so that it was pulled away from its die at the same rate it exited or emerged therefrom thereby elimin~tin~ all of the variable thermoplastic flow characteristics in the divided passages, the dies, and calibrators which it had not been previously possible to balance.
By pulling each product stream individually and adjusting the speed of pull to accommodate the flow characteristics of the thermoplastic material through the extrusion system of each product stream, it was found possible to produce precision products with significantly different profiles so that 2 o profiled products having the either the same or different profiles could be produced simultaneously.

DETALED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION

With reference to Figure 1, there is shown a conventional extruder 3 o 1 having a hopper 2 for inputting thermoplastic material to be heated to an extrusion tem~rature which may be of the order of 170 to 180 C and then delivered under high pressure. eg. of the order of 5000 p.s.i., through a nozzle 3 to a flow divider unit generally designated at 4 which divides the flow stream and feeds same to separate die assemblies generally design~ted at

7 214~19 S and 6. As shown, separate coextruders 7 and 8 are arranged to feed into the die assemblies 5 and 6 as desired. The coextruders 7 and 8 have feed hoppers 9 for introducing desired coextrusion thermoplastic material which is normally heated to a slightly lower teml?elature than the material extruded by 5 the extruder which may be of the order of 140 to 160 C and delivered at a somewhat lower pressure, eg. of the order of 2000 p.s.i., than the material being extruded by the extruder 1. While two coextruders are shown, it will be understood that if each profiled product is to be coextruded with the same m~çrial a single coextruder could be used and its output appropliately split to lo feed into the die assemblies S and 6.

The somewhat soft and rough profiled product streams 10 and 11 emerging from the die assemblies S and 6 respectively are drawn through a series of calibrating or sizing units to cool and precisely form same into the 15 final precisely profiled product streams.

As shown in Figure 1, the product stream 10 is drawn through a series of calibrators or sizers 12a, 12b and 12c while the product stream 11 is pulled through calibrators or sizers 13a, 13b and 13c.
As will be understood in the art, these sizers or calibrators 12a, 12b and 12c and 13a, 13b and 13c have internal configurations corresponding to the die configurations 5 and 6 respectively and operate under high vacuum to pull the walls of the product streams against the internal walls of the 25 calibrators providing a progressive sizing and cooling of the product streams as they are pulled through the successive calibrating units.

The required vacuum to the calibrators is provided by vacuum pumps 14 which are connected to the calibrators by lines 14' and air 30 withdrawn from the calibrators is aided in its exhausting to the atmosphere by cyclones lS.

- 8 - 2144719 As will be understood, the calibrators are water cooled to cool the profiled product stream as it is calibrated and this cooling is provided by waterlines 16 circulating cooling water therethrough.

The calibrated product stream emerging from calibrator 12c which started out as a somewhat roughly profiled product stream 10 issuing from die assembly 5 is designated as calibrated product stream lOc which now has a precise profile. Similarly, the calibrated product stream issuing from calibrator 13c is designated as calibrated product stre~m llc.
The product streams lOc and llc are pulled through the calibrators by individual pullers 17 and 18 respectively.

As hereinafter more fully explained, the speeds of the pullers 17 and 18 are individually controlled to the precisely correct speeds so that puller 17 operates to pull product stream lOc at precisely the right speed so that the product stream 10 is pulled away from its die assembly 5 at precisely the rate it emerges thel~rlolll. Similarly the speed of puller 18 is set so that it pulls the profiled product stream l lc at precisely the right speed so that the product stream 11 is pulled away from its die assembly 6 at the speed it emerges therefr~lll.

The pullers 17 and 18 which, as will be understood, are capable of exerting high pulling forces, eg. providing a torque of the order of 50,000 to 60,000 foot lbs., deliver the profiled product streams lOc and llc to a saw station generally de~i~n~ted at 19 where a pair of saws 20 and 21 cut off the proper lengths of the profiled product streams lOc and llc after they have been delivered to a dumping table station 22.

With reference to Figures 3 and 4, the flow divider unit 4 has a barrel portion 23 provided with a clamping flange 24 having slots 25 to receive bolts 26 projecting from the nozzle 3 of the extruder 1. Nuts 27 applied over washers 28 engaging the bolts 26 clamp the unit 4 to the face of the nozzle 3.

9 21~4719 A flange 29 is formed at the forward end of the barrel portion 23.
The flow divider 4 is bored to provide a Y passage formation generally designated at 30.

The leg portion 31 of the Y formation is arranged to register with the discharge outlet 32 of the extruder nozzle 3 to receive the heated thermoplastic material delivered by the feed screw 33.

0 The divergent branch or leg passages 34 of the Y passage formation are preferably equal in diameter and of the order of half the diameter of the leg portion 31 whereby material forced under pressure out of the discharge outlet 32 of the extruder is directed to divide equally between the two divergent passages 34.
A converter block 35 fastened to the face of the flange 29 by bolts 36 is bored to provide outwardly flared passages 37 to register with the outlets of the divergent passages 34 to convert the divergent flow through these passages into parallel flow streams for delivery to the die assemblies S
and 6 which include adaptor blocks 38 and 39 with feed passages 38' and 39' for inputting coextruding material and profile forming dies 40 and 41 for forming the profiled product streams lO and 11 respectively.

Figure S illustrates the profile 42 formed by die 40 and profile 43 formed by die 41.

In the extrusion process the heated thermoplastic m~teri~l is delivered out of the extruder orifice or outlet 32 and into the leg passage 31 of the Y passage formation under high pressure at a predetermined fixed rate.
This material flow is then divided between the divergent leg passages 34 which between them must accept all of the material moving through the passage 31. With the passages 34 being of equal diameter, the volume flow therethrough is basically equ~li7~d but may be effected to some extent by the differences in resistance in flow impediment offered by the dies 40 and 41 lo- 21~4719 placed in the path of flow. Basically, however, the rate at which the somewhat roughly profiled product streams 10 and 11 emerge from the dies 40 and 41 will principally depend upon the volume of thermoplastic material involved per linear unit or foot of the emerging profiled product stream.
5 The profile requiring the greater volume of material per linear unit will emerge at a slower rate than the profile requiring a lesser volume of thermoplastic material per linear unit.

Whatever the precise flow characteristics in the divided stream are lo it has been found that even when dies such as dies 40 and 41 are formed as essentially identical dies the rates at which the product streams emerge thereîlom identical dies are not precisely equal and they cannot be successfully pulled away at the same speed as by a single puller to produce two acceptably profiled products The schematic diagram Figure 7 diagr~mm~ically illustrates the pullers 17 and 18 and shows how their pulling speeds are individually controlled. The puller 17 comprises the usual upper endless belt or track 44 stretched between a driving pulley wheel 45 and a corresponding idler pulley 20 46. The belt or track 45 is provided with transverse bars or ribs 47 of suitable yieldable gripping material such as neoprene rubber or rubberized material. The drive pulley wheel 45 is driven by a stepper motor 48 whose speed can be accurately controlled from control panel 49. Immediately below the upper endless belt or track 44 is a similar endless belt or track 50 25 extending between a drive pulley wheel 51 and a idler pulley wheel not shown. A separate stepper motor 52 drives the lower endless belt or track 50 with the motors 48 and 52 being driven in synchronism so that the lower reach 53 of the upper endless track 44 and the upper reach 54 of the endless track 50 travel at precisely the same speed in the pulling direction.
It will be understood that as usual the upper and lower puller tracks 44 and 50 are relatively adjustable to change the spacing therebetween to receive and grip the profiled stream being pulled thereby, for example, the profiled product stream lOc as shown in Figure 6.

-- 11 21~719 Puller 18 corresponds to puller 17 comprising an upper endless track 55 in the form of an endless belt having transverse resilient bars or ribs56 and an endless lower track 57 comprising an endless belt having transverse 5 bars or ribs 56.

Again each endless track is driven by its own stepper motor with stepper motor 58 driving the upper endless track and stepper motor 59 driving the lower endless track with the stepper motors 58 and 59 being o driven in synchronism and controlled from the control panel 49.

To enable the stepper motors 58 and 59 to be arranged at the same side of the pullers as the stepper motors 48 and 52, the motors 58 and 59 are provided with drive shafts 60 and 61 respectively which extend through the 15 pullers and drive sprocket wheels 62 and 63 respectively which drive through chain drives 64 and 65 respectively sprocket driven pulley wheels 66 and 67.
Again the endless tracks 55 and 57 are driven in synchronism so that the lower reach 69 of the upper endless track 55 travels at precisely the same speed as the upper reach 70 of the lower endless track 57 with these track 20 reaches moving in the same direction to pull the profiled product stream through the calibers. Again it will be understood that the upper and lower endless tracks 55 and 57 are moveable relative to one another to control the spacing thereof to tightly engage and firmly grip the profiled product s~e~m such as the product stream l lc as shown in Figure 6.
By controlling the speed of the stepper motors driving the endless ~acks of the pullers, the pullers 17 and 18 can be controlled so that they pull the profiled product s~eams lOc and l lc through the calibrators 12a, 12b, 12c and 13a, 13b and 13c respectively at precisely the right speed to pull the 30 profile streams 10 and 11 away from the dies 40 and 41 at precisely the rate at which these streams emerge therefrom.

The profiled product streams lOc and l lc are delivered by the pullers 17 and 18 to the sawing station 19 at speeds which can differ substantially depending on the profiles of the streams. It is therefore necessary to provide separate reciprocal saw assemblies 71 and 72 for the two streams lOc and l lc.

The saw assemblies 71 and 72 are of the same constructions and, as illustrated in Figure 8, each comprises a reciprocal carriage 73 slidable on guides 74 and driven by a reciprocating ram 75.

The carriage 73 is provided with a product stream hold down clamp 76 which is arranged to move down into clamping position during the cutting operation.

The carriage 73 also carries a motor driven saw blade 77 which is moveable up and down into the cutting position by a ram 78.
It will be understood that when the requisite length of the profiled product stream has moved past the carriage 73 the ram 75 will move the carriage in the direction of the product stream flow at the rate of the product stream flow while the hold down clamp engages the product stream and the saw blade is swung into the sawing position to effect the cut off of the productstream. Thereafter the hold down clamp will be released and the carriage will be returned to its original position awaiting passage of a further requisite length of the profiled product stream to be fed thereby whereupon the sawing process is repeated.
With the thermoplastic flow division arrangement of Figure 4, if it is desired to change one of the profile forming dies 40 or 41, it would be necessary to shut down the extruder while the die and its corresponding calibrators are replaced unless the passage 34 thereto was blocked during this replacement in which case the extruder could be operated at a slower speed.
that is, below capacity to feed the rem~ining die.

The flow divider 79 illustrated in Figures 9 to 12 provides for selectively closing off one of the branches of the divided flow when desired.

- 13 - 21 1 ~ 719 In this case, the flow divider is provided with a mounting flange 80, a body portion 81 having a transverse passage of square cross section 82 extending therethrough and a flange portion 83. A shutter bar or plunger 84 5 is slidably mounted in the transverse passage 82 and is operated by a threaded drive 85 actuated by a hand wheel 86.

With reference to Figures 10, 11 and 12, it will be seen that the flow divider is provided with a central passage 87 extending inwardly lo through the mounting flange 80 to the transverse passage 82 to receive the heated thermoplastic m~tçri~l being delivered by the extruder 1.

The flange portion 83 is provided with divergent passages 88 diverging outwardly from the transverse passage 82 to the outer face of the 15 flange 89.

The shutter bar 84 is provided with central diverging passages 90 forming a truncated V passage formation which when the shutter bar is in its central position connect the central passage 87 in the mounting flange portion 20 to the divergent passages 88 in the front flange portion 83 to provide a Y
passage formation, of which the passages 90 form the apex of the diverging passages.

The shutter bar 84 is also provided at the left hand side as viewed 25 in Figures 10 to 12 with a passage 91 which is angled inwardly from the rear of the shutter bar 92 to the front of the shutter bar 93.

A passage 94 corresponding to the passage 91 is arranged at the right hand side of the shutter bar as viewed in Figures 10 to 12 and again this 30 passage 94 is angled inwardly from the rear face 92 of the shutter bar 84 to the front face 93.

As shown in Figure 11, when the shutter bar is moved to the right, the passage 91 connects the central inlet passage 87 with the right hand passage 88 while blocking off any flow to the left hand passage 88.

As shown in Figure 12, when the shutter bar is moved to the left, passage 94 in the shutter connects the central inlet passage 87 to the left handpassage 88 while the right hand passage 88 is blocked off.

With this arrangement when the flow is not being divided as illustrated in Figures 11 and 12 and one of the passages 88 is shut off, flow takes place only in the one open passage 88 so that no material can go to the closed off passage 88 to be trapped therein and hardened which would necessitate the difficult task of cle~ning out that passage before it could be used again.
The flow divider 79 is provided with a converter block 95 secured to the front flange 83 and provided with passages 96 registering with the outlets of passages 88 to convert divergent flow into parallel flow.

The extruder 1 is of course capable of extruding a single product having a large profile such as the product 97 illustrated in Figure 13 which requires a large volume of material per linear unit so that it takes the full output capacity of the extruder for its production.

In this case, the extruder would simply feed directly into the requisite profile forming die and its associated calibrators (not shown) as in the conventional extrusion line. In this case, as illustrated in Figure 10, the product stream 97 would be pulled by the combined pulling power of the pullers 17 and 18 driven in synchronism at the applopliate pulling speed as controlled from the control panel 49.

It will be appreciated that in principle the output of the extruder 1 could be divided into more than 2 stream flows each with its own extrusion - 15 21 4 ~ 7~ 9 die calibrators and pullers provided the extruder had the capacity to run same.

Also it will be appreciated that the divergent passage of the flow 5 dividers, eg. the passages 34 of the flow divider unit 4 need not be of the same diameter since the pullers for each product line can be adjusted to a pulling speed to compensate for the different diameters so that the profile stream emerging from each die can be pulled away at the rate it emerges therefrom.
It will be understood that variations or modifications may be made in the various components at the various stations along the extrusion line without departing from the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:

1. A method of simultaneously extruding at least two thermoplastic profiles utilizing a single extruder outputting a flow of heated thermoplastic material comprising dividing the output flow from the extruder into at least two streams, delivering each of said streams through a profile forming die to convert the stream to a profiled stream, individually pulling each profiled stream emerging from its profile forming die through a calibrating unit for that profile, and adjusting the speed of pull of each profiled stream so that the take away of the profiled stream from its respective profile forming die matches the rate at which it emerges therefrom.

2. A method as claimed in Claim 1 in which the output flow from the extruder is divided into two substantially equal streams.

3. A method as claimed in Claim 2 in which said two streams are delivered to dies having the same profile.

4. A method as claimed in Claim 2 in which said two streams are delivered to dies having different profiles.

5. A method as claimed in Claim 1 in which the output flow from the extruder is divided into at least two streams having different cross sections.

6. A method of simultaneously extruding at least two profiled thermoplastic products utilizing a single extruder outputting a flow of heated thermoplastic material and having a capacity to produce a single profiled thermoplastic profile product having a volume of material per linear unit at least substantially equal to the sum of the volumes of material per linear unit of said at least two profiled products, said method comprising dividing the output flow from the extruder into at least two streams, delivering each of said streams through a profile forming die to form same into a profiled stream, individually pulling each profiled stream through a calibration unit to calibrate same, adjusting the speed of pull of each profiled stream so that the take away of that stream from its respective profile forming die matches the rate at which it emerges therefrom, and cutting off desired product lengths of each extruded and calibrated profiled stream.

7. A method as claimed in Claim 6 in which the output flow from the extruder is divided into two substantially equal streams.

8. A method as claimed in Claim 7 in which said two streams are delivered to profile forming dies having the same profile.

9. A method as claimed in Claim 7 in which said two streams are delivered to profile forming dies having different profiles.

10. A method as claimed in Claim 6 in which the output flow from the extruder is divided into at least two streams of different cross-section.

11. Apparatus for producing a plurality of profiles from a single extruder comprising a flow divider for attachment to the output of an extruder and having a plurality of passages to divide the extruder output flow into separate flow streams, a profile forming die mounted to intercept each of said separate flow streams to produce an emerging profiled product stream, calibration means for each emerging profiled product stream, individual puller means to pull each profiled product stream emerging from each of said profile forming dies through its respective calibration means to calibrate same, means to adjust the rate of pull of each individual puller means to pull its respective profiled product stream away from its respective profile forming die at the rate it emerges therefrom, and means to cut off desired lengths of each calibrated profiled product stream.

12. Apparatus as claimed in Claim 11 in which said flow divider means divides the output stream from the extruder into two separate flow streams.

13. Apparatus as claimed in Claim 12 in which said two streams have the same cross section.

14. Apparatus as claimed in Claim 13 in which each profile forming die is the same.

15. Apparatus as claimed in Claims 11, 12 or 13 having means to selectively close off one of said separate flow streams.

16. Apparatus as claimed in Claims 11, 12 or 13 in which each of said puller means comprises a pair of horizontally extending endless belts carrying a series of transverse product engaging bars having a measure of compressibility, said pair of endless belts being arranged with one superimposed over the other with the opposing horizontal reaches thereof being spaced to engage the profiled product stream therebetween to be gripped by the said bars thereof under compressive force, motor means driving said endless belts so that said opposing belt reaches thereof travel in the same direction and at the same speed, and means to control the speed of said motor means to control the speed of said opposing belt reaches.

17. Apparatus as claimed in Claim 16 having means to adjust the compressive force exerted by said endless belts on the product stream gripped between said opposing belt reaches.

18. Apparatus as claimed in Claims 11, 12 or 13 in which each of said puller means comprises a pair of horizontally extending endless belts carrying a series of transverse product engaging bars having a measure of compressibility, said pair of endless belts being arranged with one superimposed over the other with the opposing horizontal reaches thereof being spaced to engage the profiled product stream therebetween to be gripped by the said bars thereof under compressive force, a separate motor driving each of said endless belts with said opposing belt reaches thereof travelling in the same pulling direction, said motors being synchronized so that said opposing belt reaches travel at precisely the same speed, and control means for said motors to precisely control the speed of travel of said opposing belt reaches.

19. Apparatus for simultaneously producing two separate profiled extrusions from a single extruder, said apparatus comprising a flow divider for mounting to the extruder, said flow divider having a Y passage formation formed therethrough comprising a central inlet passage of a diameter to receive the column of output flow of heated thermoplastic material from the extruder and a pair of side-by-side output passages of smaller diameter than said inlet passage diverging laterally outwardly from said inlet passage, an adaptor for mounting to said flow divider having passages therethrough adapted to register with the ends of said diverging output passages and formed to provide spaced parallel output flow passages, a profile forming die mounted to register with each of said spaced parallel output flow passages, a calibration unit for each of said profile forming dies aligned therewith, a puller for pulling product through each of said calibration units, and means to control the speed of pulling of each of said pullers.

20. Apparatus as claimed in Claim 19 in which said divergent passages have the same diameter.

21. Apparatus as claimed in Claim 20 in which the diameters of said divergent passages are one-half the diameter of said inlet passage.

22. Apparatus as claimed in Claim 19, 20 or 21 in which said profile forming dies are the same.

23. Apparatus as claimed in Claim 19, 20 or 21 in which said profile forming dies are different.

24. Apparatus as claimed in Claim 19 or 20 having slidable means for opening and closing flow through one of said diverging output passages.

25. Apparatus as claimed in Claim 19 or 20 provided with a coextruder to introduce co-extrusion flow into at least one of said profile forming dies.

26. Apparatus as claimed in Claim 19 or 20 having a coextruder associated with each of said profile forming dies to introduce coextrusion material therein

27. Apparatus for use in simultaneously producing two separate profiled extrusions from a single extruder said apparatus comprising a flow divider having means for mounting same on an extruder and having a Y
passage formation formed therethrough comprising a central passage of a diameter to receive the column of output flow of heated thermoplastic material from the extruder and a pair of side-by-side output passages of smaller diameter than said inlet passage diverging laterally outwardly from said inlet passage and an adaptor for mounting to said flow divider having passages therethrough formed to register with the ends of said diverging flow divider passages and convert divergent flows through same into spaced parallel flows.

28. Apparatus as claimed in Claim 27 having shutter bar means slidably moveable into a passage blocking position to selectively block flow to one or other of said divergent passages, and means for moving said shutter bar means into and out of said passage blocking positions.

29. Apparatus for use in simultaneously producing two separate profiled extrusions from a single extruder comprising a flow divider having an inner end provided with means for mounting same to an extruder and an outer end and having a flow splitting Y passage formation extending from said inner end through to said outer end, said Y passage formation comprising an inlet leg passage portion extending inwardly from said inner divider end and adapted to register with the discharge outlet of an extruder when said divider is mounted thereto and a V passage formation portion having an apex section in communication with the inner end of said leg passage portion and presenting outwardly diverging branch passage sections extending from said apex section through to said outer divider end.

30. Apparatus as claimed in Claim 29 in which said flow divider has a transverse slot therethrough into which the inner end of said inlet leg passage portion opens, a shutter bar slidably mounted in said slot, said shutter bar having a truncated V passage formation therethough adapted on shutter movement to be moved into and out of registration with said inlet leg passage portion, said truncated V passage formation constituting said apex section of said divider V passage formation when said shutter is moved to register said truncated V passage with said inlet leg passage portion, said shutter bar having further passages therethrough comprising a first passage to connect said inlet leg passage portion solely with one of said branch passage sections when said shutter bar is moved to register said first passage with said inlet passage, and a second passage to connect said inlet passage portion solely to the other of said branch passage sections when said shutter bar is moved to register said second passage with said inlet passage portion, and means for slidably moving said shutter.