US2559365A - Apparatus for reforming thermoplastic sheets - Google Patents

Description

July 3, 1951 E. F. MIDDLETON ET AL 2,559,365

APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed 001; 2, 1946 8 Sheets-Sheet 1 INVENTORS July 3, 1951 E. F. MIDDLETON ET AL 2,559,365

APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 194

8 Sheets-Sheet 2 July 3, 1951 E. F. MIDDLETON ET AL APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 1946 8 Sheets-Sheet 3 July 3, 1951 E. F. MIDDLETON ET AL APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 1946 8 Sheets-Sheet 4 8 Sheets-Sheet 5 VENTORS /V/00470/Y a Z% ORNEY July 3, 1951 E. F. MIDDLETON ETAL APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed oct. 2, 1946 y 3, 1951 E. F. MIDDLETON ET AL 2,559,365

APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 1946 8 Sheets-Sheet 6 I INVENTORS 5%?4 F ff/DOAfTO/V 6 794 LIX/7004570.

ORNEY y 1951 E. F. MIDDLETON ET AL 2,559,365

APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 1946 8 Sheets-Sheet '7 T m w E. F. MIDDLETON ETAL APPARATUS FOR REFORMING THERMOPLASTIC SHEETS Filed Oct. 2, 1946 July 3, 1951 2,559,365

8 Sheets-Sheet a 6%22. $Z3

T we INVENTORS EHEA Eff/0 ETO/V BY @fi-M ORNEY Patented July 3, 1951 OFFICE APPARATUS FOR REFORMING THERMO- PLASTIC SHEETS Earl F. Middleton, New Rochelle, and Carl W. Middleton, Larchmont, N. Y.

Application October 2, 1946, Serial No. 704,406

3 Claims. (Cl. 18-19) The invention herein disclosed relates to reforming sheets of thermo-plastic material; more particularly, the invention relates to forming a bead on the edge of a sheet of thermo-plastic ma= terial and the forming of various articles there from.

Heretofore, and prior to the invention herein disclosed, beads have been formed on the edge of sheets of thermo-plastic material and such sheets with the beads thereon have been shaped to form the side walls of boxes, such for example as hat boxes. However, as heretofore effected, the bead formed has been tangential to the plane of the sheet. When such sheets with such a bead thereon are shaped to form the side wall of a. box, the bottom of the box merely rests upon the bead, and must be cemented thereto. Such box constructions are expensive and are not entirely satisfactory as they lack rigidity and the cementing of the bottom to the bead is not, generally, satisfactory or permanent.

By the invention herein disclosed, a bead is so formed at the edge of a sheet of thermo-plastic material that it is off-set from the tangential relation to the plane of the sheet in such manner as to form a groove or recess between the bead and the plane of the sheet. When such a sheet is shaped to form the side wall of a box, a round hat box, for example, the recess is of slightly greater diameter than the Wall of the box and the mean diameter of the head is substantially the same as the diameter of the side wall of the box. A bottom is readily snapped or pressed into the recess and a rigid, permanent construction is obtained without cementing or otherwise securing the bottom to the bead.

A machine, forming a part of the invention and a hat box also forming part of the invention and illustrating preferred embodiments of the invention are illustrated in the accompanying drawings and described in detail below, from which description a clearer understanding of the invention may be had.

The drawings include:

Fig. 1 which is a. plan of a machine, embodying the invention, for forming beads on opposite edges of a sheet of thermo-plastic material;

Fig. 2 which is a longitudinal, sectional elevation of the same taken on the line 22 of Fig. 1;

Fig. 3 which is an enlarged, fragmentary plan of the same taken on the line 33 of Fig.2;

Fig. 4 which is a fragmentary elevation illustrating certain details of the drive mechanism;

Fig. 5 which is a transverse, sectional elevation taken on the line 5-5 of Fig. 3;

Fig. 6 which is an enlarged, transverse, sectional elevation taken on the irregular line 6-6 of Fig. 2;

Fig. '7 which is an enlarged, fragmentary elevation, partly in section of the carrier for carrying a sheet through the machine in fixed relation to a bead-forming die;

Fig. 8 which is an enlarged, fragmentary, sectional plan of a bead-forming die taken on the line 88 of Fig. 6;

Fig. 9 which is side elevation of the same taken on the line 9-9 of Fig. 8;

Figs. 10, 11, 12, 13 and 14 which are longitudina-lly spaced, in progressive relation to the movement of a sheet through the die, transverse sectional elevations of the bead-forming die, taken respectively on the lines l0|0, H-II, l2|2, |-3--I3 and I4l4 of Fig. 8;

Fig. 15 which is an enlarged, fragmentary, sectional plan of the opposite die, taken on the line l5I5ofFig.6;

Fig. 16 which is a side elevation of the same taken on the line Iii-I6 of Fig. 15;

Figs. 17, 18 and 19 which are longitudinally spaced, transverse, sectional elevations of the same taken respectively, on the lines ll-Ii, |8l8, and l9l 9 of Fig. 15;

Fig. 20 which is a fragmentary, sectional plan, similar to Figs. 8 and 15 of an alternative form of bead-forming die especially adapted for form ing a square bead;

Figs. 21,22 and 23 which are longitudinally spaced, transverse, sectional elevations of the same taken, respectively, on lines 2|-2l, 2222 and 2323 of Fig. 20;

Fig. 24 which is a diametrical, sectional elevation of a box formed in accordance with and embodying the invention;

Fig. 25 which is a similar, fragmentary, sectional elevation of an alternative form; and

Fig. 26 which is a. like, fragmentary, sectional elevation of another alternative form.

The machine illustrated in the accompanying drawing is especially adapted for forming beads on both edges of a continuously moving web or sheet of thermo-plastic material, such, for example as celloulose acetate and like thermoplastic sheets. All of the mechanism (Figs. 1, 2

and 6) may be, and is with the exception of the driving motor, mounted upon a frame designated generally by the character A. At one end of the frame there is a support B for a roll of thermoplastic, sheet material C. Proceeding in accordance with the movement of a Web of material through the machine, from right to left as seenin Figs. 1 and 2, the machine includes straightening or stress-relieving mechanism D for relieving any tension or stresses in the web which are likely to cause crinkling or unevenness in the web; carrier means E for carrying the web through a bead-forming section F is fixed and constant relation to the dies G and H; and shaping means I for shaping, in this instance, the Web into cylindrical form. The carrier means E moves the web continuously, drawing it from the roll C and through the stress-relieving mechanism D. From the stress-relieving mechanism the carrier moves the web, positively and in fixed relation to the dies G and H, through the bead-forming section F and delivers or pushes the web, with beads formed on both edges, to the shaping means I. Here, an operator severe the web at spaced in tervals to produce a continuous series of cylinders, each having beads formed at both edges.

The frame A of the particular machine illustrated in the drawings includes two, transversely spaced supports I and 2, supported in turn by uprights or standards, such as the uprights Ia and lb of the support I. In bearing brackets, hereinafter designated and described, secured on these supports, the various shafts of the machine arejournalled. The supports are spaced apart a distance such as to accommodate the greatest width of web which it may be desired to operate. The dies G and the adjacent part of the carrier mechanism E are adjustably mounted on cross beams 3 and 4 extending between and secured to the supports I and 2. These cross beams 3 and 4 have T-slots therein, and support brackets 5 and 6, respectively. The brackets 5 and 3 are attached to a sub-frame support 1 on which the die G and adjacent portion of the carrier means E are mounted. The brackets 5 and 6 are secured to, in any adjusted position, the cross beams 3 and 4 by bolts, the heads of which are engaged in the T-slots of the cross beams and nuts 8 and 9, and I and I I respectively.

At one end of the frame, to the right as seen in Figs. 1 and 2, there are provided bearing brackets I2 and I3, mounted. respectivel on the supports l and 2. These bearing brackets I2 and I 3 have slots I4 and I5, inclined to the horizontal, to receive the reduced ends I5 and I? of a spindle I8 upon which a roll or spool C is mounted and to which the roll is fixedly secured. The bearing brackets I2 and I3 form journals for the spindle I8. A tensioning device, in the form of a Prony brake, is associated with the spindle to prevent free rotation of the roll C. This consists of a brake drum I9 (Figs. 1 and 2) fixed to the spindle I8 by a set screw 20, and a brake band 2!. The brake band is fixed at one end to a fixed rod 22, passes over the brake drum I9 and has weight 23 attached to the other or free end.

The stress-relieving mechanism D consists of a series of tension rollers and means for heating the web at it passes about the rollers. Alternate rollers are at different elevations. Proceeding in the direction of the movement of the web, from right to left (Figs. 1 and 2), there are a roller 24 over which the web passes, a roller 25 below the level of the roller 24 and under which the web passes, a roller 26 at the level of the roller 24 and over which the web passes, a roller 21 at the level of the roller 25 and under which the web passes,

a roller 28 at the level of the roller 24, a roller 29 at the level of the roller 25, and a roller 30 below and cooperating with the roller 29. The roller 30 is so positioned with respect to the roller 29 that the web passes between them and is 4 finally sized and straightened in the manner of the action of a calender. The axis of the roll is also slightly advanced, relative to the direction of the movement of the web, with respect to the roller 29 and so acts to support the web as it passes to the carrier means E.

The rollers 24 to 33 inclusive are of such length as to span the distance between the frame sup ports I and 2. Conveniently, they are all journalled, at one end, in a bearing bracket 3 I mounted on the support I and at the other end in a bear" ing bracket 32 mounted on the support 2. Each roller carries an adjustable collar, 24a, 25a, 25a, 27a, 28a, 29a, and 33a respectively, which are adjusted on the rollers to the width of the web passing through the machine. The collars, in effect form edge guides, contacting and guiding the edge of the web.

Beneath (Fig. 2) the rollers 24 to 30 inclusive there is provided means for heating the Web as it passes over and under the rollers. In the particular machine illustrated in the drawings, the heating means consists of a plurality of infrared heating units 33 mounted on a support 34 and distributed to provide a uniform heating of the web passing thereover. With a positive pull on the web by the carrier means E, as will hereinafter be described, against the tension of the Prony brake device associated with the spindle I8, the web is under tension as it passes about the rollers 24 to as. In passing about the rollers, under such tension it is uniformly heated by the heating units 33. All internal and locked-in stresses are thus relieved and the web passes to the carrier means and bead-forming dies with uniform stresses throughout and without any tendency to crinkle or wrinkle because of uneven pressure due to non-uniform or locked-in stresses and strains.

The carrier means E constitutes the driving means for moving the web, and also the means for fixedly positioning the web with respect to the dies G and H of the bead-forming section of the machine as the edges of the web pass through the bead-forming dies. The carrier means pri marily consists of opposed, endless chain grippers. As seen in Figs. 1, 2, 4 and 5, a drive shaft 35 is journaled at one end in a bearing bracket 36 (Figs. 3 and 5) fixedly secured on and supported by the support 2. At the other end, the shaft 35 is journaled in an. upright bearing bracket 31 (Figs. 3 and 5) adjustably mounted on the cross member 3. The shaft 35 extends through both bearing brackets 36 and 31 .and it is splined as at 38 and 39 (Fig. 5). On one end of the shaft 35, that extending through the bearing bracket 36 (to the right as seen in Fig. 5), there is secured, for rotation therewith, a drive pulley 40. Between the drive pulley 40 and the bracket 33 there are secured to the shaft 35, a sprocket 4i and a gear 42. Between the bearing brackets 36 and 31 and adjacent the bracket 36, there is fixed to the shaft 35 a carrier-chain sprocket 43, and adjacent the bracket 31, splined to the shaft 35 but movable with the bracket 31, there is mounted on the shaft 35 a carrier-chain sprocket 44.

A belt (Figs. 1, 3 and 5) engages drive pulley 40 and a pulley 46 mounted on a cross shaft 41. On the opposite end of the shaft 41, there is fixed to the shaft another pulley 48. A belt 49 engages. the pulley 48 and an adjustable, cone pulley- 50 mounted on the shaft of an electric motor 5L. The cone pulley 50 is adjustable through a hand wheel 52 (Fig. 1) and the arrangement, of the pulleys 48 and 50 and the belt 49, constitutes Mann-r a variable speed drive well known in the art as a "Reeves drive. Through this train of pulleys, belts and shafts, the shaft 35 is driven at adjustable speed by the electric motor 5|.

Also extending through and journaled in the bearing brackets 36 and 31, there is, above the shaft 35, a shaft 53. This shaft is splined, or has diametrically opposite key ways as at 54 and 55. On the end of the shaft outside of the bracket 36 (to the right as seen in Fig. 5), there is fixed on the shaft 53 a sprocket 56. Between the sprocket 56 and the bracket 36, there is fixed to the shaft 53 a gear 51 which meshes with the gear 42. On the opposite side of the bracket 36, there is fixed to the shaft 53 a carrier-chain sprocket 58. A similar carrier-chain sprocket 59 is splined or keyed to the shaft 53 adjacent to the bracket 37 and in line with the carrier-chain sprocket 44. The sprocket 59 is, as is also the sprocket 44, movable and adjustable with the bracket 31.

Adjacent the roller 30 of the stress-relieving mechanism D there are (Figs. 1 and 3) four stub shafts, 60, GI, 32, and 53. The stub shafts 60 and 6! are secured in a pair of brackets 64a and 64b (adjustable longitudinally of the machine) mounted upon the sub-frame support 1. stub shafts 52 and 63 are secured in a like pair, brackets 55a and 35b, adjustable longitudinally of the machine, mounted on the frame support 2. On the shaft 3!], inside the bracket 64, there is loosely mounted a carrier-chain sprocket 66 (Figs. 2 and 4), and on the shaft 6|, there is loosely mounted a carrier-chain sprocket 61. In like positions, there are mounted on the stub shafts 62 and 63, respectively, carrier- chain sprockets 88 and 69.

The carrier-chain sprockets carry opposed, endless carrier-chains which are especially constructed and arranged to firmly grip the web and carry it through the bead-forming section F of the machine. To this end, an endless carrierchain 10 extends over, and engages the sprockets 59 and 66. A similar, endless carrier-chain H extends over the sprocket 44 and 61. In like manner, opposed, endless carrier-chains l2 and 13 (Fig. 6) extend over, respectively, sprockets 58 (Fig. 5) and 63 (Fig. 1), and 43 and 69.

The details of the carrier-chain construction are shown in Fig. '7. Each carrier-chain consists of a series of flexibly connected links M. Each link includes a channel-shaped member 75 (Figs. 6 and '7) between the flanges of which channelshaped member two spaced shafts 76 and 11 extend. These shafts are fixed with respect to the channel-shaped member. 16 and T! of each link, there is rotatably mounted a substantially V-shaped idler '18. The chain links, so formed, are connected together in an endless chain by straight links 79 extending between adjacent shafts of the successive carrier links. On the web portion of the channelshaped members of the carrier links, there may be rubber-like deposits 80 which, when opposed carrier-chains are forced together, grips a sheet therebetween in such manner as to prevent any slippage. A properly machined surface on the webs will also grip the sheet in such manner as to prevent slippage.

These carrier chains grip a web of thermoplastic material, draw it off the roll C, through the stress-relieving mechanism, carry it through the bead-forming section F, and deliver it to the shaping mechanism I. The bead-forming dies G and H are between the ends of the carrierchains. In drawing the thermo-plastic web or On each of the shafts The sheet through the bead-forming section F, it is important that the carrier, having received a stress-relieved sheet or web from the stressrelieving mechanism, does not permit any slippage. It should hold, and carry, both edges of the web at a particular, predetermined distance from the adjacent side wall of the bead-forming dies. To this end, the opposed carrier-chains are caused to grip the sheet with a positive grip within one-sixteenth of an inch of the adjacent side wall of the bead-forming die.

By adjusting the brackets 64a, 64b and 65a, 65?), the proper or desired tension may be secured on the carrier-chains. For effecting a positive grip upon the Web by cooperating carrier chains, tracks are provided which position the opposed carrierchains in gripping relation adjacent the dies. A track 80', having a substantially V-shaped end section 3!, complementary to the V-shape of the idlers 18, supports the chain I! so that as it passes the die G, it forms a rigid continuous gripper. The track 89 is mounted on a member 82 that is fixed with respect to the frame by screws 33.

The upper carrier chain "H1, that cooperates with the chain H, is resiliently urged into gripping relation with the chain E3 by a resiliently mounted track as. The track 84 has a V-shaped end section 85 that engages the rollers 18 of the chain it. This track 84 is secured, as by machine screws 86, to a vertically movable member or bar 8'! which is held to the frame by a member 88' that engages the side Wall of bar 81. The member 88 is secured in place by machine screws 89 which extend through enlarged openings (such as the opening 59, Fig. 6) and are threaded into the member 83. Ferrules, such as the ferrule 9|, act as spacers to prevent tightening of. the screws 89 to such an extent as to bind the member or bar 8?. At spaced intervals compression springs, such as the spring 32, act upon the bar 31 urging it downward in a direction to cause the track 84 to resiliently urge the chain it into contact with the chain H. One end of the spring 92, rests upon the bar 8'! and the upper end is engaged by a movable abutment 93. A set screw 94, threaded through a plate 95, engages the abutment 93. Through this set screw the force exerted by the spring 92 on the bar 81 may be adjusted. In like manner, the chains 72 and i3 are urged into gripping relation by a fixed track 96 supporting the chain 73 and a movable resiliently urged track 9? engaging the chain 12.

The die G consists of an elongated metal block or mold 98 having a forming cavity 99 extending longitudinally thereof and a slot I33 extending through a side wall iii! and in communication with the cavity 39. In an opening formed in the mold 93, there is inserted an electrical heating element I92 which maintains the mold at the desired temperature during operation of the machine. The mold is positioned on the machine with the slot 1 09 at the plane of the engagement of the carrier-chains i9 and H and with the side wall I0! thereof adjacent to, spaced approximately one sixteenth of an inch from, the edge or sides of the cooperating or engaging sections of the carrier-chains.

The forming cavity 99 (Figs. 8 to 14 inclusive) is circular in cross section to form a circular bead and extends longitudinally through the mold. For a portion of the length of the mold, from the entering end I33 to a point or plane Hi4, the forming cavity is inclined to the side wall Hill of the mold. From the plane I 04 to a plane I05, the

cavity is substantially parallel to the side wall IOI, and from the plane I05 to a plane I06, the cavity is inclined both to the wall IOI and to the adjacent bottom wall I? of the mold. Also, from the plane I to the plane I06, a'portion of the slot I00, gradually and progressively inclines toward the wall II to form an off-set I08. From the plane I06 to the end of the mold, the cavity and slot remains the same and are substantially parallel to the side walls IIlI and IN.

In the portion of the mold cavity from the entering end I03 to a point somewhat beyond the plane I04, there is a fixed mandrel I09. The mandrel is of such diameter that with the wall of the cavity 99, an annular cavity is formed of a width substantiall equal to the thickness of the sheet to be acted upon. The mandrel has formed thereon a boss III! which fits snugly within the cavity to position the mandrel therein, and a head III which engages the end wall I03 of the mold.

In operation, the mold is heated to soften the edge portion of a plastic sheet passing through the mold. The edge portion of a thermo-plastic sheet or web H2 is entered in the slot I00 at the entering end I03 of the mold. The web is carried through, with the edge portion in fixed relation to the mold, by the carrier means described above. As it moves through the portion of the mold between the end I03 and the plane I04, the edge portion of the sheet, because of the inclination of the cavity towards the wall I 0 I is forced around the mandrel I09, until at the plane I04, a circular bead H3 is formed on the edge of the web. In passing through the section between the planes I04 and I05, the bead II3, so formed, is set. On moving through the section between the planes I05 and I06, the bead is offset so that its axis is contained in the plane of the web and a recess H4 is formed between the bead and the plane of the web.

The die I-I (Figs. to 19) is similar in construction to the die G, except for the nature of the forming cavity. This di-e consists of a metal block or mold II5 having a forming cavity H6, circular in cross section, extending longitudinally therethrough. A slot III extends through the side wall I I8 thereof and communicates with the cavity H6. An electrical heating element H9 is received within an opening in the mold, extends longitudinally thereof and serves to heat the mold.

The cavity in the mold I I 5 is arranged to form a bead I (Fig. 19) on the other edge of the web H2. The bead I20 is circular in form and positioned Without any offset, with the axis thereof within the plane of the web. To form such a bead, the cavity I I6, is, from the entering end I2I of the mold, inclined to the side I I8 of the mold to a point or plane I22. From the plane I22 to the opposite end of the mold, the cavity extends parallel to the side II8 of the mold. However, from a plane I23 to a plane I24, the cavity inclines to the adjacent bottom wall I25 of the mold. A fixed mandrel I26 similar to the mandrel I09, extends into the cavity to a point somewhat beyond the plane I22. Thus, the edge of the sheet enters the cavity tangentially, and in passing to the plane I22, it winds about the mandrel to form the bead. Thereafter, in passing from the plane I22 to the plane I23, the bead is set, and in passing to the plane I24, the bead is shifted to bring the axis thereof into the plane of the web.

In Figs. 20 to 23 inclusive a mold or die I25 is illustrated by which a bead I26, square in cross section, may be formed. This .die also has a longitudinal forming cavity I27 therethrough and a longitudinal slot I2Ia. From the entering end I28 thereof to a point or plane I29, the cavity is circular in cross section and converges toward the side wall I30 thereof. In this portion there is a round mandrel I3I about which the bead is formed. From the point I29, to the end of the die, the cavity is substantially parallel to the side wall I30. The mandrel I3I extends part way into this parallel section of the cavity. Just beyond the end of the mandrel I3I, the cavity gradually changes to square in cross section. In this last section of the cavity, there is a square mandrel I32 having a tapered end section I33. This man drel is held in place by a longitudinal strip I34, extending from a corner of the mandrel and out through the side of the die at the slot IZ'Ia, which is widened at this section. The strip I34 has a flange I35 thereon which is secured to the wall I30 of the die. With this arrangement, the mandrel I32 may be said to float Within the cavity and the bead formed can pass freely off the end of the mandrel.

From the beadforming section F of the machine, the web passes (Figs. 1, 2 and 3) along a passage I35, provided with a cover plate I31 terminating in a partial cylindrical guide and guard I38. At the end of the passage I36, there are two pair of transversely spaced feed wheels I40, I4I and I02, I33. The feed wheels are located just inside of the beads formed on the web. Behind the feed wheels i i-0, IAII and I42, I43, there is an upwardly curved wall I44 having bead receiving channels I05 and I45 on each side thereof, which are attached to and constitute extensions of the mold cavities. As the heated web is forced along this wall, it curves with the wall I44 into cylindrical form, the end engaging the guide I38. When a cylindrical section is thus formed it is broken from the web by an operator. Thus, successive cylinders, having beads at each edge, as above described are formed. A heating element I365; is provided below the passage I35.

The feed wheels I40 and I42 are mounted upon a shaft I47 that is journaled at one end in a fixed bracket I33 extending from the frame, and a bracket I43 secured to the movable frame element I. The wheel I22 fixed t the shaft I4? and the wheel I40 is splined on the shaft. In like manner, the wheels MI and I33 are mounted on a shaft 50 journaled in the lower brackets M801. and I IQa, the wheel hi3 being fixed to the shaft and the wheel I II being splined on the shaft. The shaft I4? is driven by a chain I5I engaging a sprocket fixed on the shaft 53 and a sprocket I52 fixed on the shaft III. The shaft I50 is also driven by a chain I53 which engages a sprocket I54 fixed on the shaft 35 and a sprocket I55 fixed on the shaft I55.

Various forms of beads may be formed on the edges of the web for different constructions. In Fig. 24, there is shown a cylindrical box having beads thereon as formed in the machine illustrated in the drawing and described above. In this construction, one bead I55 is formed and offset to form a recess I5'I, as described above. A flexible bottom I53, such as a card board, plastic or metal bottom, is snapped into the recess and forms with the cylinder a rigid box construction.

In Fig. 25, an inwardly extending offset I59, spaced from a bead I5, is illustrated. The bottom I6I is received between the offset I59 and the bead I50. Fig. 26 illustrates a construction in which the square bead, above described, is utilized. In this construction, a bottom I62 is provided with a downwardly and inwardly extending, circumambient flange 163 which engages in the square bead.

In making cylindrical hat boxes, a web of thermo-plastic material is fed to the machine and acted upon as above described. However, before the web is fed to the machine it is scored transversely at spaced intervals, as at I65 (Fig. 3), and partially cut in from each edge as at I66 and I61. The distance between score lines is equal to the circumference of the box to be formed, plus a slight overlap. The scoring facilities severing the web into successive cylinders. Each such cylinder is cemented or Welded at the overlap and the bottom is then inserted.

It will be obvious that various changes may be made by those skilled in the art in the details of the structures and the procedure described above within the principle and scope of the invention as expressed in the appended claims.

We claim:

1. In a machine of the kind described for forming the edge of a sheet of thermo-plastic material, stress-relieving means including a series of vertically and horizontally spaced rollers and a pair of opposed rollers, the lower roller of such pair of opposed rollers being in advance of the upper roller, opposed pairs of movable grippers in advance of the opposed rollers for gripping the sheet adjacent the longitudinal edges thereof and drawing the sheet in fiat-wise relation from the opposed rollers, means for maintaining the sheet under tension, and means for heating the sheet as it passes over and under the vertically and horizontally spaced rollers and between the opposed rollers.

2. In a machine of the kind described for forming the edge of a sheet of thermo-plastic material, the combination comprising a forming die and carrier means movable past the forming die to carry a sheet with the edge thereof extending into the forming die, said carrier means including two, opposed, continuous carrier chains, each chain comprising a series of gripper links flexibly connected together by straight links, and each gripper link including a channel-shaped member,

V-shaped idlers mounted between the flanges of the gripper link, and a gripper pad on the web of the gripper link, a fixed track extending along the length of the forming die and fixed with respect to the die for engaging in the V-shaped idlers to fixedly relate the gripping chain with respect to the die in two, right angular directions, a movable track, movable toward and away from the fixed track for engaging the other of said chains, and resilient means acting upon said movable track to urge the chain engaged thereby into gripping relation with the other chain.

3. In a machine of the kind described for forming the edge of a thermo-plastic material, a beadforming die for forming a bead on the edge of a sheet of thermo-plastic material, means for conveying a sheet of thermo-plastic material past the forming die with the edge thereof extending into the forming die, and means for shaping the sheet into a cylinder including a cylindrically curved wall having a curl-ed edge to receive the bead formed on the edge of the thermo-plastic sheet by the forming die.

EARL F. MIDDLETON. CARL W. MIDDLETON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,305,474 Lewis June 3, 1919 1,431,476 MacInnes Oct. 10, 1922 1,999,796 Zinser Apr. 30, 1935 2,006,548 Halle July 2, 1935 2,012,833 Smith Aug. 27, 1935 2,046,047 Watkins June 30, 1936 2,112,439 Graff et al Mar. 29, 1938 2,218,227 Winnek Oct. 15, 1940 2,229,613 Strauch Jan. 21, 1941 2,260,501 Wynd Oct. 28, 1941 2,317,409 Seaton Apr. 27, 1943 2,319,099 Abramson et a1. May 11, 1943 2,320,115 Young May 25, 1943 2,323,862 Zimmerman et a1. July 6, 1943 2,327,706 Halstead Aug. 24, 1943 2,383,396 Taber Aug. 28, 1945

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