IL30474A - Method and apparatus for molding foamed cellular products from a liquid reaction mixture - Google Patents

Description

/37/3 METHOD AND APPARATUS FOR MOLDING FOAMED CELLULAR PRODUCTS FROM A LIQUID REACTION MIXTURE The present invention permits the production of large cross-sectional f-oamed products with a smooth and fissure-free outer surface. In part, the present invention i:s based upon the discovery that because of the manner in which foam reactants rise, i.e. by a mushroom effect, the rising foam itself is not capable of smoothing out wrinkles in the web which carries the foam reactants. A3 a result the rising foam may bridge over the spaces between inwardly protruding portions of such web wrinkles and entraps air or gas in the intervening spaces. This may result in the production of fissures, gas pockets and other deformations. Moreover, such deformations would be produced at or near the outer surface oi the foamed cylinder and thereby result in large material loss<; Web wrinkling results from the fact that the web, which is usually of paper (although it may bo of polyethylene or similar material) , is drawn o f a supply roll about which it is wound, in one direction (i.e. longitudinally) , and is thereafter bent to curved configuration in another direction (i.e. transversely) . Additionally, the web may be required to undergo bending in several different planes simultaneously Because of the limited flexibility and extensibility of the web, these contour changes often result in the production of wrinkles, thereby deteriorating the quality of the mold to be formed by the web.

The present invention overcomes the above-described web wrinkle problem by means of novel web guiding arrangements According to one aspect of the present invention, a web, for example a sheet of chemically treated release paper, is caused to be withdrawn continuousl from a roll and uided from an initially flat configuration to curved or otherwise contoured configurations for shaping the rising foam. The positioning and orientation of each of the various web guiding means is selected to cause the web to undergo contour changes in a manner such that stretching variations across the web width are eliminated or at least minimized. This is achieved by guiding the web so as to provide a trajectory for each element across the web width which is of equal or nearly equal total length as the web moves from a position of one contour to a position of new contour.

According to a further aspect of the present invention, special inner and outer web support means are provided whereby the web is supported continuously on both sides thereof along substantially its entire lateral extent to prevent buckling and the wrinkles which result therefrom. In this connection, it has been discovered that when the web is merely supported externally, as by an outer., channel defining support, the web will buckle if the channel is of a size and shape to cause the lateral edges of the web to form upwardly protruding walls of significant height. This buckling problem has been overcome by providing a special internal support of the same general contour as the outer support so as to define between them a slot-like channel through which the web may pass without buckling. The special internal support is specially configured so that its lower edges rise up just ahead of the upwardly rising expanding foa: Thus all along the foam-forming channel the web is supported internally in part by the foam and in further part by the internal support. invention, there are provided a plurality of individual sheets which are combined in ef novel manner to form the overall foam molding web. As illustratively embodied, three separate sheets are provided, including a bottom sheet onto which the liquid reaction mixture is poured, and two side sheets which overlap slightly each of the two edges of the bottom sheet. The side sheets are guided along in a simple arc-shaped contour, while the bottom sheet undergoes variations in contour as it passes over a pouring surface, a weir, and a final configuration surface. Because of these transverse contour vari tions, the edges of the bottom sheet (which is of constant width) recede and extend laterally as the sheet moves along. The separate side sheets, however, are not affected b contouj: variations which affect the lateral positioning of the edges of the bottom sheet. The lateral movements of the bottom sheet edges are thereby easily accommodated and no v/rinkles are produced since the overlapping edges of the bottom and side sheets easily slide over one another.

Varioxis further and more specific objects, features and advantages of the invention will appear from the .description given below, taken in connection with the accompanying drawings, illustrating by way of example preferred forms of the invention.

Fig. 1 is a plan view, partially cut away illustrat ing the main portion of a foam molding apparatus in which the present invention is embodied; Fig. 2 is a side elevational view, also partly cut away, of the foam molding apparatus <¾f Fig. 1; Fig. 3 is an enlarged fragmentary view of a portion along line 4-4 of Fig. 2 Fig. 5 is a 'e l ged cross-section viev; taken along line 5-5 of rig . 2; Fig. 6 is a f agmentary perspective view of the input portion of the foam molding apparatus of tho preceding figures; Fig. 7 is a perspective view illustrating a weir structure used in the system of Figs. 1-δ; and Figs. Λ-Β and Figs. 3Λ--Β are diagrammatic views illustrating the manner in which web wrinkling is avoided by the novel web guiding arrangements of the present invention. in the foam molding apparatus shown in Figs. 1 and 2, liquid reactant3 10, such as those described in the aforementioned patents, are poured down through a nozzle 12 onto a support surface 14, and are moved along on the support surface while they react to form a cellular foamed product 16. The surface 14 is formed by a paper web 1C. The wab 18 is a composite made up of a bottom sheet 18a and two side sheets 18b and 18c. The sheets making up the web 18 may be o£ paper; and they are treated with a coating which serves to permit release of the foamed product 16 after completion of the molding operation.

The bottom sheet 18a is withdrawn from a supply roll (not shown) by means of a pair of driven pinch rolls 20. The sheets pas3 along through a portal 22 and under the nozzle 12. The portal 22 is a structure which serves to support the nozzle 12 and the various piping and other equipment appurtenant to it. From the nozzle, the sheet proceeds through an entrance guide 23 and over a weir structure 24. From up in advance of the molding channel 26 to hold back a portion of the liquid reaction mixture until it has begun to gel.

Turning now to Fig. 6, it will be seen that the front or upstream end of the internal mold support 36 encircles the weir structure 24. As indicated above, the 6 bottom sheet 10a of the web 18 passes over the weir structure 7 24. This situation is illustrated in Fig. 6 where |the sheet 8 18a is shown to pass over the weir structure and into the mold 9 support 36. The bottom sheet 18a is considerably v;ider than 10 the weir structure itself. Accordingly, the edges of the 11 sheet are bent upwardly to guide the sheet into the mold 12 support 36. This is accomplished by means of the entrance 13 guide 23. As shown, the entrance guide has lateral guide 14 walls 56 and 58 which extend up in advance of and on each I S side of the weir structure 24. These lateral guide walls 16 actually form a chute which forms the bottom sheet 18a 17 into a particular configuration during its movement over the 18 weir structure 24. 19 In Fig. 7 it will be seen that the chute, which is 20 formed by the guide walls 56 and 58, is initially of 21 trapezoidal configuration. The chute then tapers inwardly 22 in the downstream direction, and the guide walls 56 are of 23 greater length to accommodate the constant width of the 24 bottom sheet 18a.

Thereafter, in the vicinity of the weir structure 26 24, the straight guide walls 56 blend into the curved guide 27 walls 58. Further along, as can be seen in Fig. 6, the 28 guide v/alls 58 taper outwardly in the downstream direction 9 and eventually blend with the curved surface of the mold Reverting to Figs. 1, 2 and 6, the outer sheets 18a and 18b are shown to be drawn from 3ide supply rolls 60 mounted with their axes extending in a vertical direction. The sheets 18b and 18c each pass around an associated guide roll 62. The guide rolls are slightly inclined to change the direction of motion of the sheets so that they will proceed along parallel to and in alignment with the sides of the molding channel 26.

The side sheets 18b and lfic, as shown in Figs. 1 and 6, pass along the outside of the guide walls 56 and 58 of the weir structure 24, and along the outside of the internal mold support 36. However, they do pass through arc-shaped slots defined between the mold support 36 and the mold segments 32 of the side conveyors 30, as shov/n in Fig. 4 This provides lateral support on both surfaces of each of the side sheets 18b and 18c to prevent them from buckling. Thereafter, downstream of the entrance end of the mold support 36, where it tapers upwardly, the lov/er edges of the side sheets 18b and 18c come into overlapping contact with the lateral edges of the bottom sheet 18a, thereby forming the complete composite web which forms and supports the reacting mixture.

As indicated in Figs. 1 and 2, the bottom sheet pinch rolls 20 and the side sheet supply rolls 60 are also synchronously driven with the conveyors 28 and 30. This serves to maintain each of the sheets 18a, 18b and 18c in uniform" movement and to prevent relative movement between any of the sheets and the conveyors. Thus the imposition conveyors 28 and 30 and the bottom sheet pinch rolls 20 and the side supply rolls efo are all driven in synchronism through the synchronizing driving means 34. The liquid reaction mixture 10 is poured out fro:n the nozzle 12 onto the bottom shee: 18a. The liquid runs dovm toward the weir structure 24 and into a pool 68. It then passes over the weir and proceeds along dcvm through the channel 26.

The initial portion of the foam rise is contained by the lateral edges of the bottom sheet 18a. Eventually, however, the foam rises beyond these lataral edgec; and there--after the side sheets 18b and 18c serve to provide the main lateral containment of the foam.

The side sheets 18b and 18c are initially supported fully on both sides by the mold segments 32 and the internal mold support 36, as shown in Fig. 4. However, as the foam rises, the mold support tapers upwardly away from it, as shown in Fig. 3. Thu3 the regions of the side webs vacated by the upwardly tapered internal mold support 36 are simultaneously occupied by the rising f am itself which pressee the sheets out against the outer mold segments 32 before the sheets can buckle from their own weight and form wrinkles.

It will be appreciated that because of the various configurational changes which the bottom sheet 18a must undergo in passing over the weir structure 24 and into the channel 26, its lateral edges will sequentially project and recede in the lateral direction. This lateral web movement is easily accommodated in the present arrangement by virtue of the overlapping arrangement between the side and bottom hile the lateral edge movement of the bottom sheet is eadily absorbed in a greater or lesser overlapping of the djacent sheets. In this manner the complications of trans- tting lateral edge movements nearly completely around the irth of the mold, and the consequent production of web rinkles are avoided.

Figs. 8A-B and Figs. 9A-B illustrate the manner n which the web handling arrangement of the present inven-ion operates to reduce or eliminate web wrinkling during :hanges in its contour. As shown in Fig. 8A, a conventionally guided web 80 moves along between a pair of parallel •lanes I and II; and in doing so it changes from flat to lurved contour. The plane I is defined by orthogonal lines and Yj while the plane II is defined by corresponding irthogonal lines X^and The path of web movement is ilong a third plane III defined by a line 8 between planes and II and the lines and Xjj* During the web movement, its outer edges 82 and 84 urn upwardly and inwardly to form the curved contour, while he center line 86 of the web proceeds along the center of >lane III.

Turning now to Fig. 8B, it will be seen that the ;eb center line 86 reaches plane II before the web edges 82 ind 84. As a result of this, the web edges 82 and 84 tend to continue to diverge in an upward direction as indicated by :he arrows 82ci and 84a. In order to cause the web to proceed ilong plane III and cause the web edges to follow paths parallel to this plane, as indicated by the dotted arrow 82b, 34b, it becomes necessary to stretch the outer web edges by structure 24, the center line of the bottom sheet 18a will change its path of movetnent in the Y direction. In order to prevent wrinkling, the outer edges of the web must change their path of movement in the X direction. That is, the web must taper inwardly. This inward tapering, as shown in Figs. 6 and 7 is achieved by the entrance chute walls 56 and 58. Also, as in the previous case, the amount of this taper should be chosen to ensure that each ray or longitudinal line along the web moves along a path or trajectory which is as close as possible in length to the path or trajectory of every other longitudinal line across the web. When this occurs, differential stresses are minimized and wrinkling is eliminated.

Although a certain specific embodiment of the invention is herein disclosed for purposes of explanation, further modifications thereof, after study of this specification, will be apparent to those skilled in the art to which the invention pertains. Reference should accordingly be had to the appended claims in determining the scope of the invention.

What is claimed and desired to be secured by Letters Patent is:

Claims (26)

1. In apparatus for molding foamed cellular products from a liquid reaction mixture, means defining an elongated molding channel of given cross-section extending in a direction slightly tilted from the horizontal, an elongated web for carrying said liquid reaction mixture and the products formed thereof through said channel from its higher end to its lower end, and an inner support means constructed and arranged to hold said web against the sides of said elongated molding channel to prevent collapsing and wrinkling of said web, said inner support means extending substantially completely about the interior of said channel near its upper end and then tapering back in an upward direction toward its lower end so as to extend around the interior of the channel to a point slightly above the rising foam being formed by said liquid reaction mixture at each given location along the length of said channel, whereby said web at each location along said channel is held against the interior surfaces of said channel at each cross-sectional location therealong in first part by the rising foam and in further part by said inner support means.

2. Apparatus as in claim 1 wherein said means defining said molding channel comprises a plurality of conveyors each formed with cooperating support elements contoured to form the outer surfaces of said channel.

3. Apparatus as in claim 2 wherein said inner support means is maintained stationary relative to the movement of said conveyors. ■,: .L^ «

4. Apparatus as in claim 3 wherein said apparatus,, includes means for guiding at least a portion of said web ' between said inner support means and said conveyors.

5. Apparatus as in claim 2 wherein said conveyor support elements are contoured to define a generally cylindrical contour and wherein at least the forward portion of said inner support member is cylindrical in shape.

6. Apparatus as in claim 1 wherein the. olding channel is open. at the top thereof and said inner support means is mounted from overhead suspension means.

7. A web transfer apparatus for changing the transverse contour of a longitudinally moving web without development of wrinkles, said apparatus comprising an input i-according to claim 11 guide means for guiding an incoming web^naving a first transverse contour, an output guide means for guiding said web having a second transverse contour, and web contour changing guide means intermediate said input and output guide means, each of said means being relatively positioned such that the web transfer path between said input and output guide means in substantially the same for each longitudinal line in a web passing through said apparatus whereby no stress variation is produced transversely across such web and said web proceeds along with said second contour in a smooth, wrinkle-free manner.

8. Web transfer apparatus as in claim 7 wherein said first transverse contour is a straight line.

9. Web transfer apparatus as in claim 8 wherein said second transverse contour is an arcuate line.

10. Web transfer apparatus as in claim 8 wherein said output guide means is constructed to define a first fixed path of movement for said web and wherein said input guide means is positioned to feed the web in the direction of said first fixed path from a location transversely intermediate the lateral displacement of said second transverse contour.

11. Web transfer apparatus as in claim 7 wherein said web transfer apparatus forms a portion of a molding device for forming a foamed cellular product from a liquid reaction mixture, said molding device including cooperating conveyors configured and driven to define a moving molding channel for said web.

12. Web transfer apparatuses in claim 11 wherein said input guide mparts includes web feed means synchronized to be driven through said web contour changing guide means and into and through said channel at the same rate of movement as said channel.

13. In a system for continuously forming foamed; f according to claim_n cellular material from a liquid reaction mixtureVthe comb'ina-tion of, a reaction mixture supply nozzle, a conveyor system defining a mold channel of given cross-section which moves along in a downstream direction away from said reaction mixture supply nozzle, stationary means downstream of said supply nozzle and defining various configurations to be undergone by reactants which proceed along from said nozzle and through said channel, a plurality of web sheets and associated means for drawing said sheets from a location upstream of said nozzle, past said nozzle and down through said channel, at least one of said sheets being positioned to span and ride over said stationary means, and another of said sheets being positioned in edge overlapping arrangement with said one sheet to accommodate lateral edge movement of said one sheet resulting from its passage over said stationary means.

14. A combination as in claim 13 wherein said means for drawing said sheets is synchronized with said channel to move said sheets at the same rate as said channel moves.

15. A combination as in claim 13 wherein said plurality of web sheets comprises three she&t3.

16. A combination as in claim 13 wherein said stationary means comprises a flat liquid-receiving surface tilted down . way from said supply nozzle, a weir configuration rising up from the downstream end of said liquid-receiving surf ce and a foaming surf ce extending downstream from the upper edge of said weir configuration.

17. A combination as in c laim 16 wherein said weir configuration protrudeβ upstream in the center thereof*

18. A combination as In claim Ί6 wherein said flat liquid-receiving surface and said weir configuration are formed with upstanding side walls.

19. · A combination as in claim id wherein said one sheet passes over said stationary means and between said side walls* and wherein the other .sheets pass around the outside of said side walls.

20. · A combination as in claim 13 wherein said other sheets are provided with lateral support over substan-tlally thei entire surface on. oth sides thereof in the violnlty of said stationary means.

21. ·. A method for orming a foamed cellular product having a substantially smooth continuous: surface from a liquid reactio mixture, said method comprisin the steps of pouring said liquid reaction; mixture onto a flexible web to contain the mixture* supporting the lateral portions of the web on both sides thereof during the initial stages of reaction of said liquid reaction mixture in the web as thus supported and then* during the rising of the reaotants resulting from the foaming thereof* withdrawing slightly In advance: of the upward rise of foamed material in ,a generall upward, direction the internal lateral support for said flexible web so that said internal lateral support and the rising material each provide internal web support over different regions of said web. 22· A method fo changing the transverse contour of an elongated web of sheet material as it moves in a longitudinal direction, utilizing the apparatus as

22. 1 . ■ "

23. claimed 1* claim 7, said method comprising the step of gradually shifting in* relative lateral positions of dif erent elements in said web while avoiding changes in the relative longitudinal positone of said elements. 23· A method as in claim 22 wherein the path of web movement Is changed durin said change in transverse oontour.

24. 21*· A method for changing the path of movement of a transversely contoured longitudinally moving web without generation of wrinkles* as claimed I olaim 7 said method oomprisihg the step Of tapering said web in the vicinit of said path change in a direction perpendi oular to the direction of said path change*

25. · A method for forming elongated objects of foamed cellular material from a liquid reaction mixture* as claimed in claim 13 said method comprising the steps of pouring said liquid reaction mixture onto a first sheett moving said sheet along away from the pouring location and causing the eo-moving sheet to undergo transverse contour changes which produce lateral shifting of its edges, and simultaneously causing a further sheet to move, along with said first sheet In edge-overlapping relationship* whereby said further sheet serves to provide lateral containment for said mixture during foaming thereof without being effected b tho lateral edge shifting of said irst sheet.

26. Apparatus! for.molding foamed cellular products from a liquid reaction mixture substantially as hereinbefore described and Illustrated in the accompanying drawings. : 30W 2 'ν 27· A web transfer apparatus or changing the transverse contour of a longitudinally moving web without development of wrinkles substant ally as hereinbefore desoribed and illustrated in the accompanying drawings. 28·. A method for forming a foamed cellular product having a substantially smooth continuous; surface from a liquid reaction mixture, substantially as hereinbefore desoribed and illustrated in the aooompanylng drawing®.