Fasteners engageable with loops of nonwoven fabrics and with other open structures, and methods and machines for making fasteners

Abstract

A method of forming a fastener is provided, including (a) forming, from a thermoformable material, a preform product having a sheet-form base and an array of preform stems integrally molded with and extending from the base to corresponding terminal ends; (b) heating the terminal ends of the stems to a predetermined softening temperature, while maintaining the sheet-form base and a lower portion of each stem at a temperature lower than the softening temperature; and (c) contacting the terminal ends with a contact surface that is at a predetermined forming temperature, lower than the softening temperature, to deform the terminal ends to form heads therefrom that overhang the sheet-form base. Fasteners and other methods of forming them are also provided.

Description

Complete combustion uses 9.5 moles air for each mole of CH₄, thus oxygen in the air gas mix is (2 moles O2/10.5 moles total) equal to 19.0% O₂.

The burner face is approximately 1″ wide. The web carrying the stem preform travels at speeds in the range of 20 to 200 ft/min (depending upon the product desired and operating parameters), and so a stem preform element spends only a fraction of a second underneath the burner. In this amount of time a sufficient amount of heat is transferred into the preform element to enable it to be deformed into a hook. Heat is transferred to the preform element by forced convection. Heat is transferred through the stem tops as well as sides. The amount of heat transferred to the preform element, is controlled by the position of the burner relative to the elements.

Simple steps may be followed in set-up for such flat-topping.

• • 1. Extrude and form a web of preform stems on a continuous backing, as described above.
  • 2. Set gap position of the forming roll (Gap between rolls 3 and 4) at a position that corresponds with desired hook height while stem forming is occurring. At this point stems passing through the gap will buckle since their tips are not being heated.
  • 3. Turn on the burner and, step-wise, bring the burner closer to the terminal ends of the stems. The burner position will typically vary from 0.2″ to 1″ from roll 4. The flame set-up (i.e. flow conditions) is maintained constant, so that the only variable altered is the position of the burner with respect to roll 3.

In some cases the line speed is dependent upon the amount of heat desired to be transferred to the stems. For instance, comparing 2 sets of stems, Group A: 0.008″×0.008″×0.027″ vs. Group B: 0.012″×0.012″×0.075″. Group B requires more heat per stem, and passing heat through a larger body requires more time for heat to be transferred such that Group B may run at a speed ⅓ that of Group A.

The mold cavities in roll 2, FIG. 23G, are shown in FIGS. 23I-23M. Rings 70 and 72 are placed face-to-face together in registry such that when viewed from a plan view down upon the periphery of the mold ring pair, a plus sign mold shape is provided, with fin shaped cavities of between about 2 and 3 length to thickness ratio in accordance with the provided explanation. Many sets of rings are placed side-by-side and pressed onto a shaft, providing an axial distribution of peripheral rows of cavities, FIG. 23N. The size of the cavities and their distribution is selected according to the needs of the particular fastening system being constructed. Typically a slight draft angle, e.g. of 1° is employed to enable the molded fin to readily leave its mold. As shown in FIG. 23N, solid spacer rings 73 having no mold cavities are placed between pairs of rings 70, 72. A first set of rings 70, 72 is spaced by a spacer ring from the next set, and so on. In the mold pattern of FIG. 23N the mold cavities of adjacent pairs are aligned axially of the mold roll.

In FIG. 23O, a typical off-set pattern is shown for the tool rings. Adjacent pairs of rings are off-set by 50%, as one useful pattern for enabling engagement with loops.

According to the concept of this embodiment, the plus sign cross-section stems 104 with thin fins 19, 21 when pressure-formed by conformation roll 4 will provide polymer flow in directions of the four lobes off the ends of the fins. For diaper applications, for instance, where cross-machine directionality of the hook is often important due to the orientation of the machine direction of the fastener in the diaper forming process, this can achieve better engagement with the nonwoven loop component of a diaper than by hooks formed with a round or square profile cross-section design.

To explain why the thin-fin quadrolobal stem preform will provide better cross-machine directionality, referring to FIGS. 23P and 23Q, a square stem with a circular head is shown. In the side view of FIG. 23Q a loop is shown attached to the hook. The loop extends upwardly, perpendicular to the bottom surface of the hook overhang. The case where the loop is being pulled directly away from the base of the hook can be explained by vectors as in FIG. 23R. In this case the force F exerted on the loop is shown as the vector coming from the outer portion of the hook head down to underneath of the hook head to the mid point of the stem. This vector may be explained to be the sum of a vector A that extends tangent to the circle to the point where the loop exits from underneath the bottom of the hook head, heading away from the stem, and a third vector B drawn at 90 degrees, extending from the end of vector A to the end of vector F, to create a right triangle formed by side vector A, side vector B and hypotenuse vector F. The angle Φ between vectors A and F enables vector A to be written as vector F consine Φ.

For Φ between 0 to 90 degrees, as Φ increases, vector A decreases, hence the loop becomes less likely to slide off the hook when pulled.

This case is compared with one lobe of head 18 of a thin-fin hook, as shown in FIG. 23S, a top view. The loop filament is at the end point of the stem and is being pulled directly up as shown in FIG. 23T.

In this case, by vector analysis shown in FIG. 23U, the angle Φ is greater than the angle Φ for the circles Φ_fin is greater than Φ_circle. The reason for this is, according to the present concept, the tips and short ends of a thin fin stem are deformed more compared to the long section of the fin due to greater exposed surface area to the heating conditions. The greatest overhang of the hook head then is at the end of the fin. This causes a tangent to the overhanging rim to be closer to horizontal (in plan view) than the tangent line of a similar round head, and the beginning of the widest portion of the head to be close to the end surface of the thin fin. In the case of a circular head on a stem, the widest portion of a circular head (its diameter) lies at the center axis of the stem structure rather than off-set as is the case with the thin fin.

The concept described here rests in part on the proposition that the fin tip heats locally towards its profile ends because of a higher surface to mass ratio, related to surface exposed to the localized, non-contact radiant or convection heat that reaches the side margins of the stem.

Consider the top end of the quadrolobal fins with points A on the end of one fin, B in the middle where the two fins join and C on the end of the opposite fin. When passed under a non-contact heat source points A and C are predicted to acquire more heat per unit volume of polymer and are easier to deform compared to point B. During pressure forming by roll 4, more resin is pushed off (deformed) in areas A and C compared to the middle, B, because more heat per unit volume has been transferred to the synthetic resin at those points, A and B, and therefore that resin reaches a higher temperature, and consequent lower viscosity, and more readily flows in response to forming pressure.

For a typical square stem that has a cross-section size of 0.008×0.008 inch, the head has approximately two times the width of the stem. Thus the area of the footprint of an individual hook is 0.008²×ì, or 2×10⁻⁴ inches², while the stem cross-section area is of 6.4×10⁻⁵ inches². With a thin fin stem construction of the same area of ratio of 2 to 1, (length×base=2.04×10⁻⁵), the thickness is about 0.0056 inches and the length about 0.0113 inches. For the same size footprint, comparing the angle Φ between a square stem and a thin fin stem, the angle Φ is considerably greater with the fin for the same footprint than for the Φ of the circular head, or said another way, a thin fin hook of equal peel performance to that of a circular head will have a smaller footprint on the loop surface.

Footprint is important for applications such as diapers, because a small footprint allows for good penetration into a low loop mass, whereas a larger footprint tends more to push down on the loops and not allow the crook or bottom part of the head of the hook to enter under the loops that are pushed down.

This analysis indicates, further, that one can make a thin fin hook with a footprint less than that of a round head that will penetrate loop better, and get more engagement, and it can still be such that the loop tends less to slide off than with the round head.

The relationship so-far described shows the difference between a circle and a fin when the hook and loop are being separated in tension mode, i.e. at their stages of peel which are in tension mode, when the loop is pulled at an angle close to 90 degrees to the base of the hook.

The benefits of a fin may be further explained considering the condition in which the hook is subjected simultaneously to a component of sheer loading. FIG. 23V shows a flat top hook in which the loop is being pulled back at an angle between the loop filament and an imaginary horizontal line extending across the bottom of the hook head in the X, Z plane. When angle è is introduced, with the previous vector work, an equation may be generated to show the relationship between è and Φ, i.e. the relationship between the angle at which vector A is coming off the angle between vectors A and F. Vector A is the vector in which the loop is coming around the hook and angle è is the angle relative to the bottom of the hook head. With angle è=0 degrees, the loop and hook are in perfect sheer mode and with angle è=90 degrees, the loop and hook are in perfect tension mode. This enables an equation to be generated, with the vectors added, to show a minimum no-slip condition effect, angle è minimum in relation to Φ minimum is equal to the inverse cosine of the group of cosine Φ divided by sine Φ. From this relationship a graph is created, FIGS. 23X, that shows the minimum no-slip condition relationship between Φ and è, angle Φ being the angle between vectors F and A and vector A being the force tending to cause the loop to slide off the hook. It shows that for an angle Φ of less than or equal to 45°, è minimum must be 0. A loop will slide off unless it is in perfect sheer mode for Φ equal to or less than 45 degrees. This graph also shows that there is a sharp portion of the line between Φ=45 and Φ=50 degrees. It is realized that any small increase in Φ between angles from 45 to 50 degrees results in a much larger difference in what is required for è minimum. Small improvements in Φ result in less of a necessity to be in perfect sheer mode.

An important aspect of the invention concerns the realization that small changes in the head configuration can give relatively larger benefits; hence the important advantage of the thin fin construction for peel mode. Explaining further referring to FIG. 23Y a hook component is shown being peeled from a loop component. At the bottom area of the valley between the hook and the loop component the forces are substantially in tension mode, angle è being close to 90 degrees, because no sheer force is involved. The hook is being pulled directly away from the loop at the bottom of the V during peel mode, similar to the application of forces shown in FIGS. 23P and 23T. Now, so long as the hook can hold onto the loop, as it moves up the V, angle è starts to decrease.

If a hook at the horizontal portion of the fabric is still mated with a loop, all force is in the shear mode, i.e. resisted by the stem.

This shows the importance of having a large Φ angle to avoid dependence on the è angle. It is believed the fin designs will have a higher Φ angle when compared with a standard round head product. Therefore, for any given è angle, the fin design should be less likely to slip when compared to a standard round top hook. These calculations were made with the assumption of no friction; the loop conforms to head shape, thus loop stiffness is negligible, gravity is negligible and the hook is a rigid body.

The analysis applies to a plane single fin, and to the fins 19, 21 of a plus-form hook as well, and to other configurations that provide flow or forming capabilities to increase angle Φ.

In condition where only cross-machine peel strength is important, a hook component formed with single fins lying cross-wise can be employed.

The plus-form or the “quad” configuration allows one to engage in differing directions.

FIG. 24 is a 3-D (three dimensional) view of the quadrolobal hook created with (see FIGS. 24C and 24D) fins 21′ in the X axis that are shorter than the fins 19′ in the Y axis to form a hook 10 with better loop engageability in the cross-machine direction because the profile causes more polymer in the cross-machine direction to be heated and subject to forming a hook compared to the polymer of fins in the machine direction.

In certain instances the fins 21′ may be so short that their outer tip portions are not reformed by roll 4. In such case, the X-direction fins act as supports for fins 19′.

FIG. 25 is a top view of a hook created with Y axis fins 21″ and 21′″ offset from each other, neither being at the center of the X axis structure.

In the case of FIG. 25 fins 19″ protrude at the extremities of the X axis structure beyond fins 21″, at the forming station at roll 4.

In the alternative embodiment of FIG. 25D the Y direction fins are at the extreme ends of the X direction structure.

Likewise, of course, where the effect is desired for the machine direction, the stem cross-section may be placed at 90° to that which is shown in FIG. 25D.

As shown in FIG. 25D this forms an irregular shaped hook. Under certain conditions, as shown, the head has bulbous ends and reduced width section in-between, e.g. a dog bone or bow tie configuration. Such a configuration enables a loop, that passes the widest point of the hook, to slide towards the middle of the hook, where the head is narrower, effectively trapping such loops to improve hook-to-loop engagement.

FIG. 26 is a side-view of a four feature hook created with X axis fins 21A of considerable length, and Y axis protrusions 17 that are very short in machine direction md. The Y axis protrusions 17 serve to support the hook during formation and in use as well. Importantly they reduce the foot print of the hook, allowing for easier penetration into the loop mass e.g. of thin nonwoven fabrics.

FIG. 27 is a top-view of a quadrolobal hook formed with a conformation roll having an array of embossing features much smaller than the head diameter, indicated in the form shown, as square projections. Penetration of these projections into the top surface of head 18 during its formation, serves to displace resin to a useful degree, to the undersurface though not to as great a degree as at the top surface. This provides roughness or rigidity to the undersurface and edges of the head. Such features provide mechanical obstacles or “catches” to the sliding of loops along that surface, and hence enhance loop engagement.

In other embodiments, pointed pyramidal shapes, rounded dimples and the imprint of randomly placed particles such as those of sandpaper can have like effect on the edges or undersurface of the head.

Preferably, at least three of such deformations are employed and, except in the case of relatively fine sandpaper, preferably there are less than about 15 of the deformations to avoid “wash-out” of the effect.

In certain cases the surface features of the conformation roll are selected to force resin from one X, Y location to another to enhance head overhang in some regions, decrease it in others, or provide edge friction points for improving loop engagement.

The hook form of FIGS. 28 and 28A has the head 28″ shifted to one side along axis A aligned with the machine direction. This form can be created by over- or under-driving the forming roll 4 of FIG. 23G. Hooks of this type are useful in applications that require one-directional engagement.

It is useful to explain use here of the term “superheating.” In general, the non-contact heating step described, when the gas flow rate and orifice sites are set has an established range of heating capability that is controlled by the distance of adjustment and is independent of the particular polymer. Using the set-up technique described above, the heating is readily adjusted to enable flat-topping and stabilization of the forms shaped by the cold forming roll 4. By adjusting the distance of the burner closer to roll 3, more heat than the minimum required for flat-topping can be applied. The system remains within the range of the flat-topping action. In that case, flat-topping is effective to distribute the resin and apply a shape, but a point is reached at which it is readily observed that the emerging forms have not yet frozen, and further, predictable deformation is observed.

It is realized that benefit can be obtained from this secondary, “self-forming” action.

In one case, by choosing a resin having a low heat deflection temperature, the method is useful to form rounded mushrooms of the self-engaging fastener type. For the example of FIGS. 29-29A, low density polyethylene (LDPE) having a heat deflection temperature of 113 degrees F. was employed (significantly lower than the heat deflection temperatures of 186 degrees F. and 204 degrees F., of high density polyethylene (HDPE) and polypropylene (PP), respectively). (For nylon and High Density PE, see FIGS. 30, 31.)

With a given coolant flow through the cold forming roll 4, after satisfactory flat-topping of the LDPE heads was established with frozen shapes emerging, the heater was brought closer to roll 3, and the line speed slowed to apply excess heat. As heating was increased, gradual change in the final conformation of the flat-topped product was observed. A point was reached in which, in a stable process, the rounded mushroom shapes shown in FIGS. 29-29C were produced. In this case flat-topping was effective to flatten and spread the bulbous molten polymer, and following roll 4, the mass sank and rounded to the form shown. Two components of this shape were effectively engaged to serve as a self-engaging fastener as depicted in FIG. 29D.

Thus, the embodiment of FIG. 29 is formed employing an initial preform stem of the form of that of FIG. 23C, however parameters are controlled to form a rounded upper profile. In addition or in combination with previous techniques mentioned for forming round tips, it is found that resin selection and an extra degree of melting, produced by “super-heating” at the non-contacting heating steps can be usefully employed.

By choice of low deflection temperature resin, e.g. certain polyethylenes, and either by making the fin construction very thin and or subjecting the tip portion to large heat transfer by the proximity or intensity of the flame, a condition can be obtained in which useful gravity flow of resin occurs after passing by roll 4. This condition can for instance also be obtained by maintaining roll 4 at such temperature that it does no entirely solidify the tip portions.

With higher deflection temperature resins, e.g., high density polyethylene, a useful self-bending action of outer edges of the flat-topped structure form the “J” profile mentioned.

The process of forming the stem preform by filling dead-end mold voids with polymer, does not orient the polymer. As previously mentioned, heating this preformed stem results in a ball of molten polymer at the top of the stem. After heating, the molten top is reformed with a flat or configured forming roll to form a head structure extending out in all directions to an extent dependent upon the height and mass of the reformed portion.

In the pictures of FIGS. 29, 29A a low-density polyethylene resin was chosen. The tip portions were super heated, i.e. heated in excess of that to be removed by cold flat-topping to retain residual gravity flow capability.

Following flat-topping, the flattened resin head gathers under surface tension to form a well shaped mushroom head.

Under essentially the same thermal conditions, the flattened head of nylon and high density polyethylene bent bodily to turn down the peripheral tips of the heads to provide a J profile, see FIGS. 30 and 31.

FIG. 32 is a side view of a quadrolobal hook with a curved head that has portions at the fin ends shaped as a J style hook. This is accomplished by choice of the resin of which the preform stem element is molded and appropriate control of the non-contact heating and of the end of the stem and softness of the head following reformation by the conformation roll; e.g. roll 4, to enable a degree of slump of peripheral portions of the resin following flat-topping.

The amount of heat provided prior to the forming determines whether the polymer will flow while, as shown by comparison of FIGS. 29, 29A with FIGS. 30 and 31, the type of resin determines the shape of the formed head and down the stem giving a curved head or whether the ends of the head bend down to provide the J style referred to. The resultant J form is beneficial to retain loops trapped underneath the head.

FIGS. 33, 33A and 33B, perspective, side and top views, respectively, show a quadrolobal “M” hook, so-named because of the configuration of the preformed stem from which it is formed, shown in correspondingly FIGS. 33C, D and E and FIGS. 33 G, H and I illustrate mold tooling for the element of FIG. 33.

Referring first to FIGS. 17A and 17B , that preformed stem has more polymer at the outer-most portions of the stem in the machine direction, the amount of polymer decreasing linearly moving toward the center of the stem V.

FIGS. 34C, D and E show a similar M stem preform element, oriented in this case in the cross-machine direction, and conceptually formed of two “half M” configuration stem segments, see the corresponding mold tooling shown in FIGS. 34F through 34J.

In the cases of FIGS. 17A and 34, the principle of the thin fin is employed, having more of the resin concentrated at the X direction ends of the fins, adjacent vertical surfaces of the formation. Depending upon the method of deformation, an oval such as the machine direction oval of FIG. 18 or the cross-machine “figure 8” head of FIG. 34B can be obtained. With the quadrolobal M stem of FIGS. 33 similar deformations can be obtained. In the case of the hook depicted in FIG. 33, non-contact heating provides four lobes of molten resin, concentrated at the periphery, see FIG. 33F. Flat-topping of this resin can then produce the head 18B shown in FIG. 33B. The resin, as it melts, finds the path of least resistance to be predominately at the “precipice” provided at the steep sides of the M, with the desirable result of forming a large Φ angle in the flat-topped product, according to the analysis presented earlier. If a “super heating “condition” is employed, with resins such as Nylon and high density polyethylene, J-shaped profiles are obtainable at the corners.

The M-configuration can usefully be reformed to provide a loop-engageable head by contact heating techniques as well, though potentially at slower speeds. Thus the hot roll and ultrasound techniques described above with respect to FIGS. 12 and 13 may be employed to obtain head shapes that may, in the case of ultrasound or low level heat forming by a heated roll, be more sharply defined as suggested by FIGS. 34 and 34A.

In the case of the non-contact melting followed by flat-topping, steps can be taken also to limit resin flow back toward the center of the “V” shaped void, as suggested by FIGS. 34 and 34A, for instance by limiting the non-contact heating so that only the sharp tips of the M are rendered molten, while the larger cross-sections further down the wedge-form section are rendered mechanically deformable but not molten. Following this, flat topping with a chilled roll below the softening temperature or in some cases with a heated roll at or even above the softening temperature, provides useful hooks for some applications.

FIG. 34A′ depicts the profile of a hook provided by the flame heat-cold roll technique, the thicker hook tips being attributable to the non-contacted heated resin that melted and rounded under surface tension prior to the flat topping action.

FIG. 33, the 3-D view of a quadrolobal M hook has larger outer margin portions of the hook head overhanging compared with the hook of FIG. 23. More polymer on the outer portion of the fin is created from a stem that has more polymer on the outer portion of the fins and the distribution of polymer and its proximity to the heat source decreases towards the center of the stem as shown in FIG. 33C.

According to this aspect of the invention, the more the hook heads extend past the stem is beneficial for forming a crook for better engagement, to obtain better holding of loops underneath the hook. A greater distance is then required for the loop to slide off when it is at the top of the stem. When it is at the end of the stem underneath of the head, a greater distance is required for the loop to travel around the head of the stem before disengagement hence the loop will be held better.

FIG. 34B is a top view of FIG. 34A that shows the head of the hook is formed in the cross-machine direction, showing that the bulk of the polymer has indeed been pushed out to the side.

In FIGS. 34A and 34B the Φ angle is approaching 90 degrees, in this case, being high because of the large amount of polymer pressed out to the side. At the loop along the base underneath the hook, by the stem, is at approximately the widest portion of the hook. Therefore, the Φ angle will be very close to 90 degrees and the tendency of the loop to slide off will be very low.

FIG. 34A′ illustrates a hook profile similar to that of FIG. 34A.

In FIG. 34G the tool ring shown is cut at a 30 degree angle, so that when one of the rings of these figures is flipped over and two are placed together, they provide the center two rings of the mold of FIG. 34F. The rings form a peak together, FIG. 34G. In FIG. 34F two outer spacer rings make-up the beginning and end portion of the M profile.

In FIG. 34F, the four different rings are 40, 42, 44 and 46, ring 42 being the one turned over 180 degrees and otherwise is the same as ring 44.

FIG. 35 shows another alternative of the M style hook in which a small rectangular block is placed between the two halves of the M. This design provides a bigger cross-directional hook. Referring to FIG. 35A it allows more volume of polymer to be excluded between the two hooks. When this preform formation is flat topped, even more resin is pushed out to the sides. FIG. 35A′ illustrates a hook profile similar to FIG. 35A but formed in a different manner.

FIG. 36 comprises one side of the M hook design sometimes referred to as an “N” design. It can be used by having half the rings face to the left cross-machine direction and half the rings face to the right cross-machine direction. It enables heating and flat topping a stem to make a hook that bends in one direction in the cross-direction. The benefits of this hook compared to the M hook are a smaller footprint and allowing better penetration into the loop mass, yet still having cross-machine direction features. FIG. 36A′ is a hook profile similar to FIG. 36A but formed in a different manner.

FIGS. 37-37B show a hook element again formed entirely by actions in the machine direction to have significant peel properties in the cross-machine direction.

In this embodiment a monolithic fin has a parallelogram profile in cross-section as shown in FIG. 37E, with its long sides set at an angle of 45° to the machine direction and its short end surfaces aligned with the machine direction.

As a consequence the pair of smaller opposed included angles at the corners of the stem are only 45°, creating a localized region of the tip of the stem having a very high ratio of exposed surface to mass. When exposed to non-contact heating, and in particular to the hot gases of a closely held flame heater, those corners preferentially melt, to be readily deformed by the flat topping action, and indeed, when desired, can be super-heated such that desirable “J” formations can be formed as a consequence of the flow mentioned in respect of FIGS. 30 and 31. Such hook formations have a significant component of orientation in the cross-machine direction.

On the other hand, the other set of corners with large included angle locate a large mass of resin at the cross-machine extremity available to be flattened into a strong loop-engaging disc structure having substantial over-hang beyond the upright stem surface, leading to a large angle Φ. Thus both corners of the parallelogram can contribute significantly but differently to the loop-engaging function.

Referring to FIGS. 37F and G, the mold ring MR for forming the stem preform of FIG. 37C is formed simply by forming an angular passage fully through the thickness of the metal plate that forms the mold ring, the passage having the required transverse profile end, the thickness of the mold plate thus determining the thickness for the narrow dimension of the thin fin.

The alternating male fastener pattern of FIG. 37H is achieved by orienting the parallelograms of adjacent rows of molds in opposite orientations. This is done simply by reversing adjacent mold tool rings, with a solid spacer ring SR face-to-face between each adjacent mold tool ring pair. The bands of the fastener component in FIG. 37H that correspond with the mold rings are indicated by I and I_R and the bands that correspond to the mold spacer ring are indicated by II. (“I” denoting one direction orientation of a mold ring and “I_R” the reverse orientation.)

Whereas one embodiment of the parallelogram construction may have straight-sided stems as suggested in FIGS. 37-37E, another advantageous construction, especially for relatively tall fins, for providing columnar strength, has a thickened pedestal portion of the profile. This is readily understood from the mold cavity shown in FIG. 37G, of length L₁, with shoulder, of length L_P, shown on both of the long sides.

This form is simple to manufacture. The parallelogram seen in the plan view of FIG. 37F relates to the fin structure and its mold cavity as follows. Parallelograms 430 and 438 correspond to the filet-defining stress-relieving transition at the base. The next inward parallelograms 432, 436 represent the strengthening shoulders of the base pedestal of the thin fin, and the central parallelogram 434 represents the main height of the thin fin, extending to its tip.

All of these cavity portions appearing as parallelograms in FIG. 37F extend at 45 degrees to the machine direction of the mold ring.

In a preferred embodiment, with total height L₁ of 0.05 inch, the pedestal height B may be 0.020 inch, to provide added columnar strength for the flat-topping operation, and, as well, to enable the mold to provide clearance for removal of the entire fin structure from the rotating mold by the usual expedient of turning about the stripping roll 5. The mold ring plate thickness T, may for instance be 0.010 inch resulting in a diagonal tip to tip length for the fin of 0.020 inch, a length along each side of 0.014 inch a thickness t measured normal to the long sides of 0.005 inch and an end profile thickness t_p of 0.007 inch.

Taking the length of the fin as the full length of one side of 0.014 inch and thickness t measured normal to that side of 0.005, the length to thickness ratio of this fin is 2.8.

With respect to the pointed ends of the fin, flat-topping of those regions can lead to a relatively small radius arc of considerable arc extent, with a resultant Φ angle approaching 90°.

It is anticipated when a loop is engaged on that point, the loop will be prone to pass down the sides away from the tip since it will not be riding along a directly opposed stem, but rather a stem that slants at an angle away from the end of the hook.

A sense of the loop engagement capability of the embodiments of FIGS. 37-37G is obtained from the diagrammatic perspective views of FIGS. 37I and J, taken from different points of view.

Another benefit of that hook is similar to that of the quadrolobal thin fin hook of FIG. 23, in that a footprint of size equal to that of current hooks manufactured, results in a larger Φ angle about the entire narrow end of the fin. If a loop is engaged on that end it is believed that the Φ angle will be larger compared to standard flat top products that have a square stem.

As has been indicated, the benefits of using convection heating from a gas flame and forming with a cold roll are considerable.

The process allows the polymer to become molten and permits geometric configurations of the remaining formation and the flat topping step to determine the direction of the polymer flow.

The cold roll is beneficial in that it freezes the polymer quickly. This enables high line speeds and relatively inexpensive production of hooks for high volume applications.

Another non-contact heating approach is the use of a radiant heating block the heat from the metal, through radiation, with convection, heats the tips of the stems.

As has been mentioned, another way for forming similar hooks is the ultrasonic method whereby vibration is used for localized heating and deformation as determined by surfaces of the ultrasonic horn or the anvil.

A possible benefit is to obtain desired head shapes, as a consequence of a more localized heating, avoiding effects of surface tension and hence not requiring as large a fin ratio. It may also be beneficial in providing more curvature of the heads and in making a head with a smaller thickness for improved loop penetration, but with the drawback of lower line speed.

Another method used is a hot-wire method which would be a contact method. It would be with a heated wire. When the stems pass and touch the wire they could then be formed by a forming roll or nip. Those would be the main flat-topping methods.

Other features and advantages will become apparent from the following Description of the Preferred Embodiments, the drawings and the claims.

Another aspect of the invention is a composite fabric, and the making of such fabric, on which stems have been directly molded in accordance, for instance, with the teachings of U.S. patent application Ser. No. 09/808,395 filed Mar. 14, 2001, which has been incorporated herein by reference above, followed by use of a flame of burning gas jets or the combustion products flowing from the flame, to rapidly soften the extreme ends of the stems, followed by engagement by a cooled press surface such as a cooled forming bar or a forming roll, as described therein. The numerous features of stem design and conditions of forming the male fastener member as presented here are applicable to the manufacture of such composite materials.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims

1. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each first portion having only one second portion extending therefrom, an intersection of the second and first portions occurring at a distance from the surface equal to at least half the height of the stem formation, the intersection defining a discrete transition in cross-sectional area of the stem formation that corresponds to a flat upper surface of the first portion, such that the second portions are more susceptible to deformation energy than the first portions, and are sized to form heads that overhang sides of the first portions for releasable engagement with a loop product, when deformed.

2. The hook fastener pre-form product of claim 1, wherein an area of any cross-section of the second portion taken parallel to the surface is less than an area of any cross-section of the first portion taken parallel to the surface.

3. The hook fastener pre-form product of claim 2, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 50% of the area of any cross section of the first portion taken parallel to the surface.

4. The hook fastener pre-form product of claim 2, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 25% of the area of any cross section of the first portion taken parallel to the surface.

5. The hook fastener pre-form product of claim 1 in which each second portion projects above each first portion without overhanging the surface.

6. The hook fastener pre-form product of claim 1, wherein each second portion includes at least four spaced apart projections.

7. The hook fastener pre-form product of claim 6, wherein each spaced apart projection tapers from the intersection of the second and first portions to a narrow distal extremity.

8. The hook fastener pre-form product of claim 6, wherein a wall of each spaced apart projection is angled with respect the surface.

9. The hook fastener pre-form product of claim 1, wherein each first portion is substantially rectangular in shape in transverse cross-section.

10. The hook fastener pre-form product of claim 1, wherein each second portion is substantially rectangular in shape in transverse cross-section.

11. The hook fastener pre-form product of claim 1, wherein each second portion is substantially circular in shape in transverse cross-section.

12. The hook fastener pre-form product of claim 1, wherein each first portion is substantially cruciform in shape in transverse cross-section.

13. The hook fastener pre-form product of claim 1, wherein each second portion defines a pyramid shape, the intersection of the second and first portions being defined by a base of the pyramid.

14. The hook fastener pre-form product of claim 1, wherein each of the first and second portions have different shaped transverse cross-sections.

15. The hook fastener pre-form product of claim 1, wherein each first portion is cruciform in shape in transverse cross-section and each second portion is rectangular in shape in transverse cross-section.

16. The hook fastener pre-form product of claim 1, wherein each first portion is substantially rectangular in shape in transverse cross-section.

17. The hook fastener pre-form product of claim 1, wherein the first portions are of circular transverse cross-section.

18. The hook fastener pre-form product of claim 1, wherein the second portions are cylindrical.

19. The hook fastener pre-form product of claim 1, wherein the second portions are centrally located on their corresponding first portions.

20. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each second portion including at least four spaced apart projections, an intersection of the second and first portions occurring at a distance from the surface equal to at least half the height of the stem formation, each spaced apart projection tapering from the intersection of the second and first portions to a narrow distal extremity, the intersection defining a discrete transition in cross-sectional area of the stem formation, such that the second portion is more susceptible to deformation energy than the first portion, for deformation of the second portions to form overhanging heads for releasable engagement with a loop product.

21. The hook fastener pre-form product of claim 20, wherein an area of any cross-section of the second portion taken parallel to the surface is less than an area of any cross-section of the first portion taken parallel to the surface.

22. The hook fastener pre-form product of claim 21, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 50% of the area of any cross section of the first portion taken parallel to the surface.

23. The hook fastener pre-form product of claim 21, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 25% of the area of any cross section of the first portion taken parallel to the surface.

24. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each first portion being substantially rectangular in shape in transverse cross-section, an intersection of the second and first portions occurring at a distance from the surface equal least half the height of the stem formation, the intersection defining a discrete reduction in cross-sectional area of the stem formation from the first portion to the second portion, such that the second portion is more susceptible to deformation energy than the first portion, for deformation of the second portions to form overhanging heads for releasable engagement with a loop product.

25. The hook fastener pre-form product of claim 24, wherein an area of any cross-section of the second portion taken parallel to the surface is less than an area of any cross-section of the first portion taken parallel to the surface.

26. The hook fastener pre-form product of claim 25, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 50% of the area of any cross section of the first portion taken parallel to the surface.

27. The hook fastener pre-form product of claim 25, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 25% of the area of any cross section of the first portion taken parallel to the surface.

28. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each second portion being substantially rectangular in shape in transverse cross-section, an intersection of the second and first portions occurring at a distance from the surface equal to at least half the height of the stem formation, the intersection defining a discrete transition in cross-sectional area of the stem formation, such that the second portion is more susceptible to deformation energy than the first portion, for deformation of the second portions to form overhanging heads for releasable engagement with a loop product.

29. The hook fastener pre-form product of claim 28, wherein an area of any cross-section of the second portion taken parallel to the surface is less than an area of any cross-section of the first portion taken parallel to the surface.

30. The hook fastener pre-form product of claim 29, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 50% of the area of any cross section of the first portion taken parallel to the surface.

31. The hook fastener pre-form product of claim 29, wherein the area of a cross-section taken parallel to the surface and near the distal end of the second portion has an area less than 25% of the area of any cross section of the first portion taken parallel to the surface.

32. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each second portion including at least four spaced apart projections, an intersection of the second and first portions occurring at a distance from the surface equal to at least half the height of the stem formation, the intersection defining a discrete transition in cross-sectional area of the stem formation that corresponds to a flat upper surface of the first portion, each spaced apart projection tapering from the intersection of the second and first portions to a narrow distal extremity, such that the second portions are more susceptible to deformation energy than the first portions, and are sized to form heads that overhang sides of the first portions for releasable engagement with a loop product, when deformed.

33. The hook fastener pre-form product of claim 32, wherein a wall of each spaced apart projection is angled with respect to the surface.

34. A hook fastener pre-form product for subsequent formation of a loop engaging hook fastener product, the pre-form product comprising:

a base sheet having a surface of thermoplastic resin; and

a plurality of stem formations formed integrally with the surface to protrude therefrom, the stem formations being arranged for engagement with a field of loops after deformation of terminal ends, each of the stem formations including a first portion extending upwardly from the surface and a second portion extending upwardly from the first portion to a distal end to define a height of the stem formation relative to the surface, each second portion defining a pyramid shape, an intersection of the second and first portions being defined by a base of the pyramid, the intersection occurring at a distance from the surface equal to at least half the height of the stem formation, the intersection defining a discrete transition in cross-sectional area of the stem formation that corresponds to a flat upper surface of the first portion, such that the second portions are more susceptible to deformation energy than the first portions, and are sized to form heads that overhang sides of the first portions for releasable engagement with a loop product, when deformed. occurring at a distance from the surface equal to at least half the height of the stem formation, the intersection defining a base of the pyramid, and also defining a discrete reduction in cross-sectional area of the stem formation from the first portion to the second portion, such that the second portion is more susceptible to deformation energy than the first portion, for deformation of the second portions to form overhanging heads for releasable engagement with a loop product.