CA1140717A - Air cooling system for the sizing of extruded vinyl siding - Google Patents

Abstract

U>S 34,328 ABSTRACT OF DISCLOSURE

An improvement in the apparatus and process of producing extruded resinsiding, for example polyvinyl chloride, in which there is an extruded siding passed through a cooling and sizing section wherein the improvement is in the provision of notches or cut out portions along the edge of the upper plate-like former surface and the direction of cooling air onto the edge and immediately adjacent areas of the siding and formers, some of the air being directed at close proximity to control what areas are cooled and to obtain higher cooling efficiency on the desired areas, with the result being a higher temperature drop on the siding through the apparatus as improved but with a greater temperature drop on the hanger and butt edges of the siding than on the panel which is observed to have provided improvements of (1) increased line rate, (2) reduced off specification product and (3) improved heat properties.

Description

()7~7 1 The present invention relates to a method of

2 manufacturing siding from thermoplastic resin material.

3 More particularly, the invention concerns an improvement

4 in the apparatus and method of cooling and sizing of S the siding.
6 Generally, the method of producing siding 7 from thermoplastic resin materials comprises the extrusion 8 of siding through a die orifice generally conforming to 9 the cross sectional shape of the siding, followed by cooling and sizing steps. The hardened siding is cut 11 to the desired lengths and may be subjected to further 12 machining or manufacturing. The resins most usually 13 emp?oyed are polyvinyl chloride resin material, although 14 other thermoplastics may be used.
Prior to extrusion, the resin may be formulated 16 with pigments (such as titanium oxide to produce white 17 siding) or other constituents, such as lubricants 18 (paraffins), antioxidants (BHT), flame retarding additives 19 (chlorina'ed waxes) and the like.
There are various properties which are desirable 21 for the siding. One of the most obvious is the ability 22 of the siding to retain its configuration when applied 23 to a surface and exposed out of doors. One such property 24 is retention of the surface and linear appearance of the siding on exposure to heat. Some resin siding has a 26 tendency to buckle or bulge, which is referred to as 27 '`oil canning". The "oil can" test so called determines Al t7~L7 l whether a particular siding undergoes this warping under 2 specified conditions. To pass the test, no warping ~ust 3 be observed under the test conditions.
4 It is an advantage of the present invention that the siding produced thereby will withstand vigorous 6 oil-can test requixements without warping and that the 7 manufacturing line can be operated at higher speeds. It 8 is a further advantage of the present invention that the g imp-ovement described herein may be made on existing equip-ment.
ll The present invention is an improvement in 12 the apparatus and process for manufacturing resin siding.
13 Briefly, the apparatus of the present invention 14 is an improvement in an apparatus for making thermoplastic siding which has a butt edge, a hanger edge and an interven-16 ing panel comprising an extruder with a die having a 17 substantially horizontally oriented orifice which sub-18 stantially conforms to the cross section of the siding, a 19 cooling and sizing section downstream from said die and a pulling means downstream of said cooling and sizing 21 section, said cooling and sizing section having a lower 22 forming surface composed of a plurality of curved templates 23 for imparting curvature to the siding panel with the con-24 cavely curved side presented upwardly and at least one up-per forming surface covering a portion of said lower form-26 ing surface and composed of a curved plate corresponding 27 to the curved templates and means for delivering air 28 for cooling into said cooling and sizing section, wherein 29 the improvement comprises a plurality of notches along edges of said curved plate adjacent to the locations of 31 said butt and hanger edges and extending to e~pose a portion 32 of said panel adjacent to said butt and hanger edges when 33 said siding is in place in said apparatus and a plurality 34 of means to direct air onto a portion of the upper and lower forming surfaces along the edges and adjacent por-36 tions thereof corresponding to the butt and hanger edges 1 of the siding, at least some of said air means being 2 proximate to the ~utt and hanger edges and the panel area 3 adjacent thereto.
4 In addition to the coolin~ means directed specifically onto the edges of the former and at close 6 proximity thereto there may be other sources of air such 7 as blowers generally above and below the entire former 8 section which tend to cool over a portion of forming sur-9 faces generally. Generally the cooling air is drawn from 10 the surrounding environment and is ambient and is generally 11 in the range of 50 to 80F more preferably 60 to 70F.
12 The air means proximate to the area of the 13 lower and upper former surface edges performs an important 14 function in that the temperature difference along these 15 edges ~ T) is greater than ~ of the central portion of 16 the formers. It is believed that the rapid cooling of 17 the edges and the slower cooling of central portion of the 18 siding as obtained accordin~ to the present invention are 19 the reason for the improved siding material which gives 20 higher oil-can test results (i.e., will withstand higher 21 temperatures without buckling or warping), 12ss off 22 specification product and higher production line rates.
23 The more rapid cooling of the edges is further 24 obtained by the notches in the upper former surface which 25 expose the siding passing thereunder. By this means, the 26 sizing and shaping function of the upper former is maintained, 27 since only a portion is removed and the increased cooling 28 obtained.
29 It has also been found that at least the central 30 portion of the upper former surface should be insulated to 31 prevent too rapid cooling of the central portion of the 32 panel. The portion of the upper former surface around the 33 notched areas may be similarly insulated to further control 34 the cooling of the edges of the siding. These adjustments 3~ may be made for each instal~ation and manner of operation 36 in order to optimize the process.

1 The lower former surface is comprised of a 2 plurality of vertical spaced templates. Hence cooling air 3 directed from the lower side of the apparatus readily finds 4 its way onto the siding through the open structure of the templates. The adjustment of this flow of air in 6 conjunction with the flow onto upper former surface is 7 again a mechanical adjustment easily made to optimize each 8 particular apparatus.
9 In addition to the apparatus discussed above, there may be an embossing roll located between the extruder 11 and cooling and sizing section, where various patterns 1~ such as wood grain may ~e added to the siding.
13 The process of the present invention comprises 14 extruding a thermoplastic resin at a temperature sufficient to plasticize said resin, generally over 300F and pre-16 ferably 350 to 400F in a generally linear path into a 17 continuous belt thereof having a butt edge, a hanger edge 18 and an intervening panel, and passing said belt through 19 a cooling and sizing section, said belt of thermoplastic resin is hardened into siding wherein the improvement com-21 prises in a first zone supporting the lower surface of 22 said belt to form a concave upper surface, and applying 23 cooling air onto said butt and hanqer edqes and the adjacent 24 area of said panel on the uPper and lower surface thereof from sources proximate thereto, in a second zone support-26 ing the lower surface of said belt and enclosing a portion 27 of the upper surface of said belt to form a concave upper 28 surface and applying cooling air on the butt and hanger 29 edges and the adjacent area of said panel on the upper surface thereof from sources distal thereto ànd in a third 31 zone supporting the lower surface of said belt, enclosing 32 a portion of the upper surface of said belt to form a con-33 cave upper surface and appl~ing cooling air onto said butt 3~ and hanger edges and the adjacent area of said panel on the upper surface thereof from sources proximate theretoO

5 --1 In a preferred arrangement further cool air 2 is subsequently applied to the upper surface of the belt 3 from a distal source, However, the siding is in its com-4 pleted form at this point and the further cooling is to bring the product closer to room temperature.

6 The invention will be better understood by

7 reference to the drawings wherein:

8 Fig. 1 is an overall outline view of the major

9 components of the equipment.
Fig. 2 is a schematic view of the process manu-11 facturing line.
12 Fig. 3 is a perspective view o~ a portion of 13 the former of the first zone of the cooling and sizing 14 section-Fig. 4 is a cross sectional representation of 16 the siding material extruded and passed through the 17 apparatuS~
18 Fig. 5 is a cross sectional representation of 19 the former of the second zone of the cooling and sizing section.
21 Fig. 6 is a cross s~ctional representation of 22 the former of the third zone of the cooling and sizing 23 section.
24 Fig. 7 is a perspective view of a portion of the upper former of the third zone of the cooling and 26 sizing section.
27 An extruder apparatus A is shown in Fig. 1 28 at-the right end of the siding production line. The 29 extruder is adapted to receive powder polyvinyl chloride resin compositions and to heat and plasticize the resin 31 then deliver it into and through an extrusion die B. The 32 extrusion die is formed of various passages, including an 33 inlet passage for receiving the plasticized resin from the 34 extruder and a discharge orifice of cross sectional shape suhstantially conforming with the cross section of the 36 siding.

13L4~ L7 1 After the siding exits from the discharge 2 orifice of the die, the siding is still soft or in 3 plasticized condition and is passed through a pair of 4 nip rolls D, the upper one of the pair being an embossing roll, to thereby impart a grain texture to the face of the 6 siding. After leaving the embosser, the siding passes 7 into and through the cooling and sizing section C, wherein 8 the siding is hardened in the desired cross sectional 9 shape and form.
The siding F is advanced through this cooling 11 and sizing section hy means of the puller mechanism E, 12 after which the siding is cut in the desired length, nail 13 holes are punched or other machinery operations performed.
14 Although the extruder as represen~ed in Fig. 1 is of the multiple screw type, a variety of known types of 16 extrusion equipment may be used. Similarly, although the 17 particular embodiment depicts an extruder adapted for 18 delivery of the resin (preferably polyvinyl chloride) as 19 a powder, other feed systems adapted for receiving and plasticizing pellets, prill or granules may be employed.
21 The die will substantially correspond to the 22 cross section shape of the extruded siding, with appropriate 23 allowances as known in the art to compensate for swelling 24 and/or shrinkage of the extruded resin and produce the ~5 hardened end product of the desired shape and size.
26 After leaving the embossing rolls D, the siding 27 enters cooling and sizing mechanism C which is comprised 28 o~ three zones 10~ 12 and 14 ~hich are described more fully 29 hereafter. ~Blo~rers 1~, 18, 20 and 2~ are shown as possible sources of t~e cooling air as discussed below, although 31 a single plant supply can be used for any or all of the 32 air sources and any other ~hich may be added. In this 33 regard, it is desirable to have a final air hood G, which 34 i~ located between the cooling and sizing section C and puller mechanism E which (air hood G) blows directly onto 36 the entire upper and lower surface of the hardened and ~L4~7~L7 1 substantially cooled siding. This last cooling occurs 2 after the desired "oil can" properties are obtained by 3 the control of the cooling and sizing section zones and 4 merely removes heat in a substantially equal manner from the entire siding.
6 The cooling and sizing section is comprised of 7 three subsections or zones lO, 12 and 14, in which the cool-8 ing and sizing of the still sot siding is accomplished.
9 Although each zone is somewhat similar to the other zones, there are variations which have been devised to obtain ll the desired improvement in line speed and product quality.
12 Each zone contains a former which facilitates the shap-13 ing of the siding. Each zone in addition to having a 14 somewhat different former is also separately controllable as to the cooling which occurs therein. It should be 16 appreciated that the former and the cooling are closely 17 related and their interdependent relationship is the means 18 of the improved results.
l~ Each zone contains a lower former surface. The lower former surface is substantially the same in each 21 zone and is shown in ~ig. 3. Fig. 3 is a perspective 22 view of the first zone lO into which the moving siding 23 passes. This zone has only a lower former 30 which is 24 comprised of a plurality of templates 40 which are spaced apart and arranged vertically so that the lower surface 26 Of the siding is contacted by only the thin edge of 27 templates~ thereby reducing the drag or friction as the 28 siding passes through.
29 The lower former in each of the other two zones 12 and 14 are substantially the same as that of zone lO.
31 The lower former templates are supported in each zone by 32 bars (not shown~ which pass through openings 41 and 42.
33 In the preferred apparatus zone lO, 12 and 14 have a 34 similàr number of templates spaced about the same distance apart, The spaciny is obtained in the usual manner with 36 spacers (not sho~n~ on ~he bar ~not shown) between the ~C~7 1 templates and appropriate gripping means (not shown) 2 such as nuts threaded on the bars and attached to sup-3 port means (not shown) in each 20ne. Generally about 4 four inch spacing of templates is usual in zones three feet long.
6 The templates have a concave surface adjacent 7 to the siding which serves to shape the sidin~.
8 Turning now to a consideration of the cool-9 ing arrangement in zone 10, two sets of air bars are located on each side of the former adjacent to the butt 11 edge 43 and the hanger edge 44 of the siding. Fach air 12 bar 31, 32, 33 (hanger edge) and 34, 35, 36 and 37 (butt 13 edge) has openings 45 therealong which direct the air 14 therefrom onto the respective edges of the siding as it passes, but not onto the central panel section of the 16 siding. The air bars are held in place by members 46 17 and 47 and the members and air bars are mounted by any 18 conventional means in zone 10. For example, the members 19 46 and 47 may be attached to hinged elbows (not shown) which are subsequently attached within the zone in order 21 to be retractable from the rormer templates 40 for ser-22 vicing and repair of the latter.
23 It should be apparent that each zone 10, 12 24 and 14 is enclosed in a chamber shown ir Figs. 5 and 6 25 which has an opening at two opposite ends along the 26 machine line. The chamber provides the means of control-27 ling the temperature and also provides the structure onto 28 which the various former and cooling components are 29 attached. This is all quite conventional and details to the attachment of these components in the chamber are not 31 necessary for one of ordinary skill in the art in order to 32 obtain the novel improvement in apparatus and equipment 33 as disclosed herein.
34 Fig. 4 shows schematically how the air bars deliver air onto siding 48 to obtain cooling, primarily 36 of the hanger edge C and the butt edge A while omitting ~L4V~

1 the ma j or portion of the panel portion B . In this zone 2 the air bars are 1/2 ID tubing having 1/16 inch diameter 3 holes spaced 2 inches apart therealong. The air was de-4 livered to the tube at 5-50 psig as required at about 50-60F. The small arrows in Figs. 4, 5 and 6 represent 6 direction of air flow.
7 The former of zone 12 is aepicted in Fig. 5.
8 The former comprises the templates 40 as described in 9 zone 10 which comprise the lower surface, and the plate 50, which extends the length of the templates of zone 12 11 and which has a curved surface corresponding to the curve 12 in the templates 40, and which forms the upper former 13 surface. The upper former surface is hingedly mounted 14 (not shown) on the left hand side to be raised off of the lower former surface 40 in the same dir~ction as the 16 hinged cover 51 on chamber 53. Means (not shown) are 17 also provided to space the right hand side of upper former 18 surface (plate) 50 the appropriate distance from the 19 lower former surface (templates) 40. Air i5 supplied to this zone 12 by air hood or cover 51 through flexible 21 conduit 54 and is directed generally downward in the 22 area of the hanger and bu~t edges of the siding, although 23 it is not directed thereon with the close control of the 24 air bars of zone 10, for example. The lower former tem-plate 40 is shown mounted on bars 56 and 57.
26 The plate 50 has notches along the edges cor-27 responding ~o butt and hanger edges of the siding, as 28 shown in Fig. 7, which is the upper former 60 of zone ~9 14, differing only in the extension of the insulation 55 over the entire surface of the upper former surface 31 60 including the lips on either side of the notches.
32 Fig. 6 represents the Placement of the former 33 in the third zone, zone 14. There are templates 40 34 spaced apart and the upper former surface, lplate) 60 has the configuration shown in Fig. 7. The upper surface 36 of the plate is covered with insulation 62 except for the 1 lips 63 which extend on either sides of notches 67. A
2 rib 61 is located at the end of the plate and can provide 3 the point for attachment of hinges in order to hinge the 4 upper former as the hood 68 is provided with hinges 6~ on 5 the left hand side of chamber 70.
6 Two air bars 71 and 72 previously described for 7 zone 10 are located above the upper former to direct air 8 at close proximity onto the exposed portion of upper former g surface 60, the siding passing notch 67 and the adjacent

10 han~er and butt edges.

11 A xefinement and preferred manner of construc-

12 tion of the upper formers 50 and 60 is the asbestos cover-

13 ing 64 shown in Fig. 7 which is on the side toward the

14 siding. This additionally insulates the central panel

15 area of the siding. The air bars of zones 10 and 14 are

16 about 1 to 2 inches away from the surfaces on to which the

17 air is directed.

18 To demonstrate the improvement that has been

19 obtained by the present invention, it can be noted that

20 the previously operating manufacturing line producing 8

21 inch wide polyvinyl chloride siding was able to run at up

22 to about 250 pounds per hour output of finished siding with

23 variable properties on the "oil can" test, generally up

24 to about 125F. After modification of the production line according to the present invention, production was 26 raised to greater than 300 pounds of product siding per 27 hour with average "oil can" test results of 150+F.
28 Referring to Fig. 2, a schematic of the present 29 system is shown. The temperature at four comparable points 30 W, X, Y and Z was measured for the prior apparatus and 31 the present invention at a, b and c points of Fig. 4 on 32 the siding which shows:

PrevioOus Process PresentOInvention 3 Positlon a b c a b c 5 X 25~ 235 260 250 230 260 6 Y 200 255 230 160 ~00 155 8 This shows that the cooling of the central panel of the g siding is reduced and the cooling of the outer portions 10 increased in the cooling section.
11 In the oil can test three sections of 6 foot 12 length siding are mounted on a vertical wall. A six foot 13 long heat source consisting of infrared heat lamps with 14 a maximum watt density of 6Q0 watts/lineal foot is mounted 15 32 inches from the wall facing the test siding.
16 A thermocouple is attached to the back slde of 17 the siding. The heat passing ~hrough the siding is recorded.
18 The test requires that there be no buckling or warping 19 (oil canning) up toa specified temperature; present~y Canada 2~ requires the siding pass the test at 120F and a somewhat 21 lower requirement is required in the United States of 22 AmeriCa-23 As extrudate resin siding grows in use, it can 24 be expected that higher performance requirements will be

25 made and that closer specifications will be required. The

26 present improved process obtains a more uniform and pre-

27 dictable product with higher performance.

Claims (11)

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

1. In an apparatus for making thermoplastic siding which has a butt edge, a hanger edge and an interven-ing panel comprising an extruder with a die having a sub-stantially horizontally oriented orifice which substantially conforms to the cross section of the siding, a cooling and sizing section downstream from said die and a pulling means downstream of said cooling and sizing section, said cooling and sizing section having a lower forming surface composed of a plurality of curved templates for imparting curvature to the sizing panel with the concavely curved side presented upwardly and at least one upper forming surface covering a portion of said lower forming surface and composed of a curved plate corresponding to the curved templates and a means for delivering air for cooling into said cooling and sizing section, wherein the improvement comprises a plurality of notches along the edges of said curved plate adjacent to the location of said butt and hanger edges and extending to expose a portion of said panel adjacent to said butt and hanger edges, when said siding is in place in said apparatus and a plurality of means to direct air onto a portion of the lower and upper forming surfaces along the butt and hanger edges thereof, at least some of said air means being proximate to the butt and hanger edges and the panel areas adjacent thereto.

2. The apparatus according to claim 1 wherein said cooling and sizing section comprises three zones, said first zone comprising only said lower forming surfaces and a plurality of proximate air sources about said forming surface to direct air onto the butt and hanger edges and the adjacent areas of the panel thereto; said second zone com-prising said lower and upper forming surfaces and a plurality of distal air sources to direct air onto the butt and hanger edges and the adjacent area of the panel thereto; and said third zone comprising said lower and upper forming surfaces and a plurality of proximate air sources to direct air onto the butt and hanger edges and only the upper surface of the adjacent areas of the panel thereto.

3. The apparatus according to claim 2 wherein the proximate air sources of the first zone comprise a plur-ality of air bars clusted about the butt and hanger edges, the distal air source of the second zone comprises a blower and the proximate air of the third zone comprise an air bar over each of said butt and hanger edges.

4. The apparatus according to claim 2 wherein an additional distal air source is located downstream of said cooling and sizing section, and prior to said pulling means for directing air over said entire siding on the upper surface thereof.

5. The apparatus according to claim 2 wherein said first, second and third zones each comprise a chamber having openings along the machine line of the apparatus for passing said siding therethrough.

6. The apparatus according to claim 2 wherein said upper forming surfaces each comprise a plate having a plurality of notches along the edges corresponding to the butt and hanger edges and extending over a portion correspond-ing to a portion of the panel.

7. In a process for making thermoplastic sid-ing which has a butt edge, a hanger edge and an intervening panel comprising extruding a thermoplastic resin at a tempera-ture sufficient to plasticize said resin in a generally linear path into a continuous belt having a butt edge, a hanger edge and an intervening panel, and passing said belt through a cooling and sizing section in which said belt of thermoplas-tic resin is hardened into siding, wherein the improvement comprises in a first zone of said cooling and sizing section, supporting the lower surface of said belt to form a concave upper surface, and applying cooling air onto said butt and hanger edges and the adjacent area of said panel on the upper and lower surface thereof from sources proximate thereto;
in a second zone of said cooling and sizing section, support-ing the lower surface of said belt enclosing a portion of the upper surface of the belt to form a concave upper surface and applying cooling air onto the butt and hanger edges and the adjacent area of said panel on the upper surface thereof from sources distal thereto; and in a third zone supporting the lower surface of said belt, enclosing a portion of the upper surface of said belt to form a concave upper surface and applying cooling air onto said butt and hanger edges and the adjacent area of said panel on the upper surface thereof from sources proximate thereto.

8. The process according to claim 7 wherein the temperature of said extruded thermoplastic resin is in the range of 350 to 400°F.

9. The process according to claim 8 wherein said thermoplastic resin in polyvinyl chloride.

10. The process according to claim 8 wherein the air in the cooling zones is at a temperature in the range of 50 to 80°F.

11. The process according to claim 10 wherein the pressure of the air leaving the source in the cooling zones is in the range of 5 to 50 psig.