CONTINUOUS MOLDING OF FASTENERS AND THE LIKE

Abstract: Continuous molding of objects, such as fasteners with filament-like portions (24), using a rotatable molding wheel with peripheral orifices. Plastic is extruded through a manifold (36) upon the periphery of the wheel (40), and a knife assembly (42) in eliptical contact with the wheel is used to skive film from the molded objects. Then selected portions of the objects can be stretched (47), by using diverging sprocket wheels (220).

Description: CONTINUOUS MOLDING OF FASTENERS AND THE LIKE . BACKGROUND OF THE INVENTION Tliiβ Invention relates to continuous molding and more particularly to the continuous molding of objects such as. fasteners. Many objects can be produced by molding. Examples are fasteners set forth and disclosed in U.S. Patent Nos... 3,103,666; 3,165,367; 3,299,183; 3,399,132; 3,300,122; 3,111,597; 3,157,589; 3,170,831; 3,191,003; 3,650,151; 3,650,152; 3,652.001; 3.659,769; 3.733,657; 3,731,375; 3,759,135; 3,875,618; 3.893,612;- 3,895,753; and 3, 18,128; 1,039,078 and 1,121,187. Plastic r ' aβtenerβ In accordance with .the Toregolng patents have been provided in aβsemblieβ of limited length for feeding sequentially through dispensing devices. In U.S. Patent 3,103,666 the fasteners are in clip attached by βeverable necks to a runner bar. In U.S. Patent 3,875,618 the fasteners are In the form of a stock of continuous side members cross-coupled by a plurality of filaments. . Fastener assemblies employing runner bars are limited in the number of items which can be conveniently supplied in a single assembly. The runners and associated connectors also waste material * While the fastener stock described in ϋ.S * Patent 3,875,618 partially overcomes these limitations, it has proved costly to produce such..stock. OMPI The continuous molding of plastic objects such as ribbed film, zipper fasteners, and the like has been proposed in U.S. Patent Nos. 3,196,196; 3,391,113; 3,139,798; 3,115,915; 3,505,159; 3,509,005; and 3,515,778. However, the methods of these patents are not readily applicable to the molding of many objects, such as fastener stock. The dimensions of many objects are often small. Precision and uniformity are often required for subsequent use, and provision must often be made for clean spaces or" windows". Consistent molding without flash or filming Is not easily achieved, and the removal of film I jraises many difficulties. Thus the. removal or defliming of flash with heat as suggested in U»S, Patent 3,509,005 can damage the stock- Accordingly, it is an object of the invention to facilitate the continuous molding of objects,' particularly plastic fastener stock. A related object is to facilitate the molding of attachment stock with transversely extending filaments. Further objects of the invention include the Improvement of the extrusion process, for-example alignment of an extrusion orifice with the surface of a molding wheel, by provision of control over the .parameters of the stock, and by alteration of the stock parameters without damage. Another object of the inveniion is the provision of stock of consistent quality in rolls or assemblages or any desired length and quantity. Still another object of the invention is to expedite the formation of fasteners for the attachment of items. Λ related object is to expedite the formation of assemblages of attachments. Yet another object of the invention is to facilitate the stretching of continuously molded fasteners. A related object is to facilitate the stretching of continuously molded assemblages of attachments with transverse filaments. Other objects of the invention will become apparent from the description of the invention set. forth below. 5UMMA1.Ϊ OF THE INVENTION - • In accordance with the invention, a molding wheel is mounted for rotation about its axis and is provided with ' mold cavities about its periphery. The cavities are complimentary in shape to the desired stock. . In the case of fasteners, the portion of the cavities corresponding to cross-members have edges at the wheel surface substantially parallel to the axis of rotation. Λ manifold is provided with an arcuate surface substantially complementary to a portion of the peripheral wheel surface. The manifold has an orifice spaced from the adjacent wheel cavities. Plastic is extruded under pressure through an orifice of the manifold to fill the cavities and form over them a film of predetermined thickness. Λ knife is used to skive the film from the plastic in the cavities. The knife is mounted to hold its cutting edge in substantially eliptical contact with the wheel surface at an angle to the axis of rotation. The desired eliptical contact can be provided by clamping one " or more flexible thin blades in elipticaly shaped Jaws, or by providing one or more tapered O PI - WWIIPPOO blades which can be deflected as cantilevered beams to form an eliptical arc. A mechanism is preferably provided adjacent to and in advance of the knife to hold the plastic in the cavities during skiving. To provide alignment. between' the orifice of the manifold and the surface cavities in the molding wheel, as well as to maintain a controlled thin film over the cavities, it is desirable for the manifold to have a surface complementary to a portion of the wheel and an orifice slightly recessed from the wheel. The recessed orifice Is- at a controlled distance, and the manifold is preferably mounted on the ' extruder by a universal Joint. A suitable universal Joint is a ball and socket Joint with a ball fixed to the extruder. A fluid passage through the universal Joint communicates with the orifice. The socket is provided by a complementary cavity in the rear of the manifold and a clamp secures the manifold to the ball. This permits a small movement of the manifold in any direction when the wheel is brought into molding position. It also provides automatic alignment. The wheel desirably has circumferentially extending bearing surfaces on either side of its cavities, and the complementary manifold surface includes bearing surfaces on either side of the manifold orifice. In operation, the wheel is moved against the manifold, rotated and hot plaβtlcunder pressure is extruded through the ball and manifold orifice. This fills the cavities and forms a film over them of several thousandths of an inch in thickness, for example about 2 mils. The wheel is advanced from the orifice to a skiving position where the knife skives the film from the fastener stock at an angle to the wheel's axis of rotation, and the stock and film are removed. The film is recyled through the extruder. Any suitable pressure used to extrude plastics can be employed, for example from several hundred to one thousand or more pounds per square inch. The stock may be further treated,, in the case of fasteners, for example, to stretch the cross-members. In particular, the cross-members of fasteners are stretched by r being engaged by members which are spaced apart and rotate in non-parallel planes. In accordance with one aspect of the invention the engagement members rotate and the fasteners are integrally formed from ' stock with opposed side rails with cross¬ links. The engagement members, which are desirably in the form of wheels, have a minimum peripheral separation which is ho greater than the portion of each fastener that is to be stretched, and diverge at least to a maximum peripheral separation corresponding to the portion after stretching. Each engagement wheel preferably has a plurality of radial projections spaced apart at the cross link intervals. In addition the mounting of the wheels is desirably made adjustable to vary the angle of divergence and thus the amount of stretching imparted to each cross link. In operation the fastener stock is fed continuously into engagement with the rotating engagement wheels. The cross links of the stock are then stretched by the diverging wheels and the stretched stock is thereafter removed by continuing the rotation of the wheels, which converge and thus release the tension of the stretched fasteners. OMH DESCRIPTION OF THE DRAWINGS Other aspects of the Invention will become apparent after considering several embodiments of the invention taken in conjunction with the drawings in which: Figure 1A is a plan view of a set of objects in the form of fasteners fabricated in accordance with the invention; Figure ID is a side view of the objects of Figure 1A; Figure 2 is a plan view of another set of objects in the form of a further set of fasteners fabricated, in accordance with the invention; Figure 3A is a schematic elevational view of a. continuous molding in accordance with the invention; Figure 3B is a vertical section of the manifold and the mount for the apparatus of Figure 3A; Figure 3C is a plan view of the- apparatus of Figure 3B; Figure 3D iβ a Tront view of the manifold shown in Figure 3B; Figure 3E is a partial horizontal section on the line E-E of Figure 3A; Figure 1A is a front view of the ball employed to mount the manifold of Fig 3B; Figure B Is a front view of an orifice insert for the manifold of Figure 3Λ; Figure 5Λ is a side view to an enlarged scale of the skiving knife and mounting means ' therefor; Figure 5B is a front view of the knife and mount of Figure 5Λ; Figure 5C is a bottom plan view of the wheel and skiving knife; Figure 6A is a view of stretching apparatus for use in the system of Figure 3A in accordance with the invention; Figure 6B IS a side view of the apparatus of Figure 6Λ showing the stretching of fastener stock; Figure 6C is a perspective view of the rearward engagement portion of the apparatus of Figure 6A; Figure 6D is a perspective view of the diverging frontal portion of the apparatus of Figure 6A; and Figure 6E Is an enlargement of a portion -of Figure 6B Illustrating the stretching of fastener stock in accordance with the invention. DETAILED DESCRIPTION With reference to the drawings, Figures 1 and 2 illustrate types of fastener stock which are readily fabricated in accordance with the invention. It will be understood that other objects can be fabricated as well. This stock oT Figures 1A and IB is more fully described In copendlng application Serial No. 827,276, riled August 21, 1977, the disclosure of which Is incorporated by reference. The stock of Figures 1A and IB Includes .end members 20 and 22 and a plurality of spaced filamentary cross-members .21. The members 20 are provided with connectors 26 of reduced- cross section and the end members 22 are similarly provided with connectors 28. The stock further includes a molding strip 11 which is separated from the stock after fabrication and before use. In use, the connectors 26 and 28 may be severed from the stock to provide Individual fasteners, each with a transverse bar 20 and a paddle 32 at opposite ends of a flexible filament 21. The transverse bar 20 may be fed through the bore of a hollow needle for the Joining or tagging of objects. Another kind of stock in accordance with the invention is shown in Figure 2. This stock also Includes end members 20' and 22' and a plurality of spaced leg members 21'. The end members 20' are provided with connectors 26' and the end members 22' are similarly provided with connectors 28'. As before a molding strip 11' is included which is removed from the stock before use. The individual fasteners of Figure 2 include two leg members 21' and one corresponding end member 22*. The head portion 22' is in the form of a hook that can be used to hand merchandise, such as socks from rods after the end members 21' have been driven into, for example, respective socks of a pair. The driving mechanism may again employ a hollow needle through which the end members are driven. A molding system according to the present invention is shown schematically in side elevation in Figure 3Λ. The system includes an extruder 31, a manifold assembly 36, a manifold mount 38, a rotatable molding wheel 10, a skiving knife and hold-down assembly 12, a take-off roll 11, transfer rolls 15 and a windup roll 19« The fastener stock may be passed prior to wind-u ' p through stretching apparatus 17 of any suitable type, for example as shown in Figures 6A through 6E, below, to decrease the size of filaments 21 and Increase their strength and flexibility. A mounting plate 18 is provided for mounting the knife 12 and transfer rolls 15« The axis of rotation for the wheel *I0 extends through the plate 18. The plate 18 together with a mechanism (not shown) located behind the plate for driving the wheel and rolls may be mounted on one or more rallβ 50 for moving the molding wheel 10 toward and away from the manifold 36. As shown In Figure 3E, the wheel JJO is provided with a series of circumferential cavities 12 complementary in shape to the fastener stock. Indicated by broken lines in Figures 1Λ and IB is a disposable feed strip 11. This aids in filling the cavities and supports the stock during removal and handling. A corresponding cavity 11' is provided in the surface of the wheel 10. The strip 11 is Joined to the end. member 22 by a plurality of frangible connectors by which it can be removed an recycled to the extruder. If desired, the molding wheel 10 can be provided with an additional circumferential circumferential set of cavities fed from the opposite side of strip 11 to form simultaneously two strips of fastener stock. The manifold 36 and its mounting assembly are shown in enlarged Figures 3B-3D._ The manifold assembly 36 comprises a curved portion 16, provided in three segments 46a, 16b and 16c Tor convenience of. construction and handling, a mounting plate 53, a main plate 51 having in its rear face a ball socket 52 not subtstantially exceeding a hemisphere in size, and a clamp 51. The manifold 36 Is mounted on a rod 56 which terminates In ball 58. The rod 56 is in turn rigidly ' mounted on the extruder 31. The rod 56 and ball 58 are provided with a paβageway 60 to provide fluid communication between the extruder and the orifice 62 in the manifold 36. Projecting Into the passageway 60 is a rounded flow rod 61 which is adjustably inserted into passageway 60 to control the flow of plastic and aid in mixing. The manifold and ball assembly are heated by a plurality of electrical heaters 66 and suitable temperature transducers 68 are provided to monitor temperature. As shown in Figure 3B, the manifold base plate 51 is mounted over the end of the ball 58. and the clamp 5 bolted thereto to secure it in position. T e cavity in plate 51 and clamp 1 provide a socket for the ball 58. The cavity and ball form a universal Joint which permits universal movement of the manifold with respect to the extruder to automatically align the manifold with the wheel. The ball 58 is provided with a plurality of grooves 70 through which plastic under pressure may exit between plate 51 and clamp 5 in the event the wheel and manifold assembly OMM become blocked. A sealing ring 72 is provided on the surface of the ball socket 52 which seals the grooves 70 during normal operation. Relief slots 71 may also be provided in plate 19 for a similar purpose. As shown in Figure 3D, the arcuate segments 16a, 16b and 16c are bolted to the plate 19 which is in turn bolted to the plate 51 by bolts 76. Segments 16 include bearings 78 and 80 at each outer edge which bear against bearing surfaces 79 and 81 on the wheel 10, the wheel bearing surfaces 79 and 81 (Figure 3E) extending circumferentially.around the wheel on either side of the molding cavities. The middle segment 16b is provided with an insert 82 which is in fluid communication with the passageway 60 and which terminates at its outer.surface with orifice 62 of any suitable shape, for example as shown In. Figure B. By employing an inβert, ' the orifice can be readily changed in response to wear or to the requirements of different molding wheels. The Insert 82 is secured in the segment 16b by any suitable means, for example by brazing. The outer surface of the manifold portion 16 adjacent the molding wheel and inter e.diate the bearing surfaces 78 and 80 is recessed slightly by an amount sufficint to form a controlled film over the molding cavities of a thickness of a few mils, preferably about 2 mils. While the recess may be uniform, it Is sufficient to provide βuch clearance at one point downstream of the orifice, for example, at the edge 81 of segment 16b. Elsewhere, the clearance may be greater. As shown in Figure 3B, the recess is increased from edge 81 upstream of the molding wheel by an arc substantially equal in radius to that of the molding wheel but with its center of rotation above the center of rotation of the wheel. e recess downstream in segment 16c may be substantially greater as shown. As shown in Figure 3Λ, the wheel is rotated past the manifold 36 where the mold cavities are filled with fluid plastic under pressure and a uniform film formed thereover, and the wheel is rotated approximately 270 degrees to the skiving knife assembly 12 where the film is removed by skiving. The mold Is cooled, for example with water, to solidify the plastic in the cavities. » - Since the cavities required to mold plastic fastener stock of the type described herein have ' a succession of transverse cavities of substantial length, it is desiraVle to skive the film from the surface of the 'wheel at a cutting no t l ine/paral lel to the axis of rotation. The placement of the knife edge is at an angle to the wheel axis of rotation. This requires substantially an el iptical arc of contact and a cutting edge with a corresponding el iptical shape. This eliptical shape can be provided by one or more thin flexible blades, such as razor blades, mounted in the clamping Jaws of a holder In which the contacting surfaces, of the jaws are machined or otherwise formed in the required el lptlc shape. Preferably, two such blades are employed. g _ OMPI More preferably, the knife is machined from thicker and βtlffer metal. The knife blade can be machined to the required shape, for example, according to the equation: X 2 - SIN 2 A + Z 2 + (D/2) 2 , where X is the horizontal axle, Z is the vertical axis, A is the skew angle, and D is the diameter of the molding wheel. However,the machining of such blades Is expensive and there is no simple way to sharpen It. A satisfactory blade of uniform thickness cannot be provided by deflecting Its ends,. while holding the center fixed, because the resulting beam curvature is proportional to the bending moment and decreases from the center support to the tip. This Is the opposite of the curvature required in an ellpβe. It has been found however that the beam can be tapered from a thick portion, either at the- center or at one end, to decrease the moment of Inertia of the beam enough to overcome the effect of the decreasing bending moment and, as a new result, yield a beam whose curvature increases outwardly in substantially an eliptical arc. The blade 95 has a center support 96 attached to the thick center " 98 in which the upper surface of the blade is linearly tapered toward each tip 99 and 100. CMPI The required angle of taper for any given wheel, may be determined by trial and error. The approximate taper may also be calculated, conformity determined on the molding wheel, and final adjustments made by slowly Increasing the taper. One such method of calculation is disclosed in an article entitled: "DEFLECTION AND SLOPE IN TAPERED BEAMS", Baumeister and Sebroβky, Machine Design, December 28, 1972. The taper can also be approximated by solving the following equation, assuming a slight taper as an initial approximation: d 2 y/dx --M/EI—12W(L-x)/Ew[h 2 +h 1 -h 2 /L(L-x)] 3 where x is the absissa, y Is the ordinate, L is' the beam length W Is the fσroe applied to the end of the.beam, h j is the beam height at the support end, h 2 Is the beam height at L, w is the beam width, M is the bending moment, and I is the moment of Inertia. In use, the knife edge should be tipped slightly, for example about 5 degrees, to the center tangent of the wheel. While not essential, a slight increase in taper to compensate for such tipping is beneficial. The knife can be tipped in any suitable manner. The upper surface of support is machined at 5 degrees to the horizontal for mounting to a horizotal plate as described below. A mount for the knife 95 is shown in Figures 5A-5C. It Includes a plate 110 terminating in a horizontal base 112 to which the center support 6 of the blade 95 is bolted. Base 112 has Its center line parallel to the axis of rotation of the molding wheel and has two locating bolt holes for the support 96 which are located off-center to dispose the knife at the desired skew angle, .for example 15. degrees, as shown in Figure 5C. Adjustable screws 130 and 132 are provided at the ends of base 112 to deflect the ends of knife 95 to contact the surface of the wheel. As shown in Figures 5B and 5C, plate 110 Is secured to plate 116 which extends through plate 18; An arm 120 is fixed to plate 110 and carries , a rod 122 to which a flexible spring finger 121 is secured to dispose its free end 126 in contact with the surface of the plastic film immediately in advance of the knife, for example by a distance of about 20 mils. As shown in Figure 5C, arm 120 is bolted to plate 110 at an angle which permits a flat rectangular spring to be employed. While a single tapered blade 95 Is Illustrated, supported In the center and tapering toward each end, two or more blades can be employed one or more of which are mounted at one end and tapered toward the other end. The optional stretching mechanism 17 of Figure 3Λ can take a variety of forms. One suitable form makes use of diverging sprocket, wheels as shown in Figures 6A through 6D. For simplicity the fastener stock 11 (Figure 6E) is formed by longitudinally extending side members 10a and 10b which are Joined together at regular intervals by a succession of unsbretched, transversely extending cross connectors 12. It will be appreciated that the fastener stock 11 can be made In any suitable fashion and take a wide variety 'of forms. The fastener stock typically is a unltized plastic structure manufactured, for example, of nylon, polyethylene, ' polypropylene, polyurethane, or other similar material. The only limitation on the stretching is that it not exceed the tensile limit of the material. Individual fasteners are provided from the stretched stock by severing the side members 10a and 10b between adjoining filaments 12 to provide a fastener with cross bars on the opposite ends of each filament. With reference to Fig. 6A, an apparatus 17 for stretching stock in accordance with the.invention is formed by a pair of rotatable wheels 218 and 220 with projections 222 and 221 spaced around their peripheries for engaging successive cross members of the stock at intervals substantially equal to their distances of separation. The wheels 218 and 220 are rotated by synchronous motors 226 and 228 at substantially the same speed, and are angularly mounted with respect to one another such that extensions 230 and 232 of their planes of rotation converge In an acute angle. As a result, the wheels have-a position of maximum convergence 231 and a position of maximum divergence 236 at an angular displacement of -100°. The motors 226 and 228 are pivotally mounted to permit variation of the angle between the wheels as Indicated by the arrows 238 and 210. This can be accomplished by using clamping bolts in an arcuate track (not shown). A change in the angle between the wheels 218 and 220 and the accompanying variation in the divergence .236, permits different lengths of stretched filaments to be made from a single length cross bar. As indicated in Fig. 6B the unstretched fastener stock 11 Is fed mechanically or manually under a feed bar 212 and over projections of the two wheels, such as the projections 221 of the wheel 220, at a point where the wheels converge with a distance between them no greater than the length of the unstretched cross connector 12. Opposed pairs of projections, such as the projections 222 and 221 as shown In Fig. 6C engage opposite ends of each cross connector to advance and simultaneously stretch the connectors as the wheels diverge. Stretching continues until the wheels 218 and 220 reach their position of maximum divergence 236, after which, as indicated in Fig. 6D, pairs of projections converge and release the stretched filaments. The stretched stock Is then removed at a bar 211, as illustrated in Figs. 6C and 6D. The only condition Imposed on the wheels 218 and 220 is that they He in converging planes. The point of maximum convergency 231 of the wheels 218 and 220 is illustratively less than the length of any unstretched cross connector 12, and the point of maximum divergency 236 is equal to the length of the stretched filament. If desired, however, the gap 231 may equal the length of the unstretched connector and the maximum divergency 236 may be somewhat greater than the desired length of the stretched filament, especially where the plastic material possesses resilience. It has been found, for example, that the stretching of fastener stock in accordance with the invention is beneficial even where the material stock is so resilient that it returns to nearly Its original length af er stretching. While the unstretched fastener stock 11 is shown being fed onto the projections * at the peripheries of the wheels near the position 231 of maximum convergence, the stock may be fed at any other position where the wheels are spaced apart a distance no greater than the length of the unstretched cross connectors 12. Similarly, it is preferred that the stretched stock be advanced beyond the position of maximum stretching 236 to facilitate removal. However, the stretched stock may -be forcibly withdrawn at an earlier position, particularly if the maximum divergency 236 exceeds the desired stretched length of the fastener. Fixed peripheral projections are preferred and shown for retaining the fastener stock on the engagement wheels. Any other suitable retainer, however, may. be employed. For example, the peripheries of wheels 218, 220 may be grooved to receive end members 10a and 10b with clamps that retain the end members in the grooves during stretching. It should be further understood that the present Invention Includes all modifications and equivalents within the scope of the appended claims. OMPI

Claims: I CLAIM: 1. Apparatus for continuous molding comprising: (a) a molding wheel mounted for rotation about its axis and having cavities therein; and (b) a manifold surface substantially complementary to a portion of the wheel surface and having an orifice spaced from the molding wheel. 2. Apparatus according to claim 1 including means for fortαinga film on said molding wheel. 3 * Apparatus according to claim 2 further comprising means for contacting said film in advance of a knife' and adjacent thereto to hold plastic ι n said cavities during skiving. 1. Apparatus according to claim 3 wherein the knife comprises at least one blade tapered from a thicker portion toward at least one end, an< *. mounting means being adapted to fix the thicker blade portion and deflect the tapered end toward the wheel. 5. Apparatus according to claim 3 wherein the knife comprises a thin, flexible blade and . mounting means comprising, aclamp adapted to bend and hold the blade cutting edge in the shape of an eliptical arc. 6. Apparatus according to claim3;. wherein the knife comprises a plurality of blades and mounting means fadapted to hold each blade in contact with a portion of the wheel surface. 7« Apparatus according to claim 2 further comprising universal means for mounting the manifold to the extrusion means to provide automatic alignment of the manifold with |the wheel. 8. A method for continuously molding plastic objects including fastener stock having parallel end members cross-coupled by a plurality of cross-members and from which individual fasteners inαluding one of the cross-members may be severed, the method comprising the. steps of: (a) providing a molding wheel mounted for rotation about its axis and having circumferential mold cavities; (b) rotating the wheel past a substantially fixed orifice; and (α) extruding plastic under pressure into the cavities to fill them. 9. A method as defined in claim 8 further including the steps of: (d) forming over said cavities thin continuous film; and (e) thereafte skiving the film from the plastic in the cavities at an angle to the axis of rotation of the wheel while reβiliently holding the plastic in. the cavities. 10. Plastic fastener stock of the type having elongate substantially parallel end members cross-coupled by a plurality of cross-members and from which Individual fasteners including one of the cross-members may be ,8or severed,produced by the method of claim 9, or by the apparatus of claims l-7« OMPI . WHO

Inventors: RUSSELL DAVID BATES, RUSSELL, DAVID, BATES
Applicants: DENNISON MFG CO, DENNISON MANUFACTURING COMPANY
Application year: 1984
Main classification: B29C17
IPC codes: B29C47, B29C55