US 3408705 A
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NOV. 5, 1968 J KAYSER ETAL I 3,408,705
FFFFF NEH ART ICLES Filed July 7, 1966 WWMM TOR/V636 United States Patent 3,408,705 FASTENER ARTICLES James H. Kayser, St. Paul, Minn., and William C. Flanagan, Jr., Hudson Township, St. Croix County, Wis., assignors to Minnesota Mining and Manufacturing Com pany, St. Paul, Minn., a corporation of Delaware Filed July 7, 1966, Ser. No. 563,520 7 Claims. (Cl. 24-204) ABSTRACT OF THE DISCLOSURE Fasteners comprising pairs of unitary interengaging articles. Each article has a base carrying a multiplicity of headed engaging elements over its surface. The positions of the element heads are unordered with respect to each other. This lack of order makes the engagement force of the articles much more uniform at all relative angles and positions of engagement than if the elements were ordered, e.g. in rows.
This invention relates to fasteners, and more particularly to fasteners comprising mechanically interacting functional surfaces which can be engaged without regard to alignment.
Various types of fasteners comprising complementary pairs of articles capable of engaging and holding to one another over an area or surface are known, e.g. see US. Patents 2,499,898 and 3,192,589. The individual articles of these fasteners have functional surfaces with patterns of headed elements located in ordered positions relative to one another on a base. The patterns usually consist of straight rows of equally separated elements. When the articles are engaged, the element heads of each are held between the element heads and the base of the other.
The fasteners of these patents are satisfactory for some uses, but if an attempt is made to interengage them at random angles relative to one another (e.g. at relative angles at which the rows of elements in one article are not parallel to those of the complementary article), either engagement is impossible, the surfaces are damaged (many elements being broken) or at best an unsatisfactory engagement is achieved (a relatively large force being required to engage and a relatively small force being required to disengage).
The need to carefully align the prior art fastener articles before engaging them considerably limits their utility since in many applications in industry and in the home,
it is impractical or inefiicient to align the complementary fastener articles precisely when mounting them for use. Furthermore, when the complementary articles are mounted on rigid substrates (such as metal or wood), they cannot shift and adjust to one another upon engaging.
A second general type of fastener in which the complementary articles hold over an area is exemplified by US. Patent 2,717,437. These articles can be interengaged at random angles, but have a low degree of holding power and are substantially dilferent in operation and constuction then either the previously mentioned types of fasteners or those of the present invention.
It has now been found possible to provide fasteners which do not require careful alignment before engagement, which have a high degree of holding power and are relatively easily manufactured. Elements are not damaged and the force required to engage the fasteners and the force which resists separation is quite uniform, regardless of alignment.
The fasteners of the invention comprise complementary pairs of interengaging unitary articles each having a relatively stiff base from which emanates a multiplicity of resilient cam elements, each comprised of a stem ter- 3,408,705 Patented Nov. 5, 1968 minating in an enlarged shaped head, the position of each element head being unordered with respect to the positions of the other element heads.
They combine a high degree of holding power with properties of operation and holding which are substantially independent of the relative angles at which the surfaces engage and of the positions of the surfaces which are engaged (i.e. the properties of engagement are substantially independent of angular and translatory changes in relative positions of the complementary articles). Thus, they can be considered to be essentially isotropic in nature. In any position of engagement, many or most of the elements of the surfaces are out of their normal no-stress positions (i.e. their positions when not engaged). The direction and extent of the stress and strain of any individual element being generally unordered and unpredictable when the surfaces are engaged.
Various illustrative embodiments of the invention, including certain features which are discussed hereinafter, are shown in the accompanying drawings wherein:
FIG. 1 is a top view of an article of the invention having elements with heads of uniform circular cross section, the elements being in unordered positions. The stems are hidden behind the heads and are not shown.
FIG. 2 is a fragmentary side view of an article of the type shown in FIG. 1 in which the elements have essentially spherical heads of a uniform size.
FIG. 3 is a fragmentary side view of an article of the invention having elements with bullet-shaped heads.
FIG. 4 is a top view of an article of the invention in which ordered sub-groups are located at unordered positions, the sub-group configuration being such that the centers of the elements therein are in a triangular relationship to one another.
FIG. 5 is a fragmentary side view of an intermediate in the preparation of still another article of the invention showing several unheaded element stems which are cylindrical in shape, the ends thereof being planes which are at acute angles to the axes of the cylinders.
FIG. 6 is a fragmentary side view of an article of the invention having unsymmetrically headed elements, said article being prepared by heating the article of FIG. 5 from the ends of the elements to melt them and form the heads.
FIG. 7 is a fragmentary side view of an article of the invention having elements of varying lengths with stems and essentially spherical or globular heads of varying diameters. In FIGS. 2, 3 and 5-7 a depth of field ofonly one to two elements are shown for clarity.
The individual elements are stiff, spine-like and elastic and are unitary with the relatively rigid and stilfbase of the unitary articles. The latter preferably remains substantially undeformed during engagement and disengagement of the articles. The elements tend to resist positional displacement but normally bend to the side like cantilever beams in response to forces brought about by engagement movements of the articles. This resistance to positional displacement (which is transmitted from element to element through the base) is important in providing the high degree of holding power of the fasteners.
The term unordered as used herein refers to the relative positions of the element heads on a single fastener article and means a lack of mathematical predictability thereof. It can result from a lack of order in the positions of entire individual elements, of the heads of individual elements or of the orientation of unsymmetrical element heads. In any of these cases, the elements are unordered (i.e. their positions cannot be predicted). The unorder may appear in only one or in more than one of the coordinates used to describe the locations thereof. Thus, for example, using the rectangular coordinate system to describe the positions of the elements, the length and width measurements might be ordered but the height measurement unordered and hence the location of any element head would be mathematically unpredictable.
FIGS. 1-3 of the drawings provide clear illustrations of articles of the invention in which the entire individual elements are unordered. Articles having the element heads at unordered positions, as in FIG. 1, but in which the element stems are attached to the base at ordered positions also have essentially isotropic properties and fall within the invention.
FIG. 4 illustrates articles containing ordered sub-groups of elements which sub-groups are unorderd in their relation to one another. Such surfaces are generally unordered and their performances are substantially isotropic as are those of the other articles of the invention.
In contrast to the surfaces of the present invention, ordered arrangements of element locations indicate mathematical predictability, i.e. mislocation or omission of an element therein could be detected as could elements present in addition to the pattern.
Although the functional surfaces of the articles of the invention (those carrying the headed elements) are unordered, certain overall limitations thereon are generally applied. Thus, sufiicient overall space is provided between elements so that engagement is possible, yet there is a suflicient density of elements so that strong engagement is achieved.
The overall density of elements per unit area and ranges of permissible sizes and shapes thereof can be used to control these factors. The density of elements can be limited by restraints on the distances between elements, such as minimum or maximum distances, proportions of distances, etc. or by limiting the volume of space wherein elements may be located. The positions of heads may also be related to the stem diameter, or other parameter.
The engagement movements of the fasteners of the invention involve the movement of the heads of the elements of each article past those of the other article and include the initial engagement of the articles, the shifting of relative positions of engaged articles, in certain cases, and disengagement. The element heads of each complementary article of the fastener bear against those of the other during engagement movements and holding in engagement is provided when element heads of each article are held between the element heads and base of the other (i.e. below the element heads of the other). Each engagement movement is accompanied by the clastic deformation of a great majority of the cam elements within the proportional limits of the elastic material and then at least partial recovery from deformation when the new position is reached. The behavior of any particular element or elements in any particular engagement may not be typical of the majority, e.g. an element may be simply bent to the side but its head not pass by the heads of the adjacent elements of the complementary article. Also a particular element may be elastically deformed during interengagement but may not recover even partially upon reaching the engagement.
Preferably the surfaces of the invention are capable of undergoing simultaneous operational engagement over the entire surfaces although in some particular articles of the invention simultaneous engagement is difficult or impossible and sequential engagement (e.g. engagement progressing from one side of the functional surfaces to the other) is used. Even where not necessary the bases can sometimes be deformed, for convenience, eg to bring about sequential engagement in articles in which simultaneous engagement is possible but more difficult. Also the base of an engaged article can be made concave and disengagement or a change in engagement thereby made difficult or impossible.
Among the variables in the design of the fasteners 4 are the length, diameter, shape, composition, stiffness and angle of intercept with the base of the element stems; the composition, shape, size and resistance to volume deformation of the heads; and the thickness, shape, composition and stiffness of the base. Preferably, in the articles of the invention the element heads are at a uniform distance above the base since such articles are more easily manufactured and perform quite satisfactorily. In addition the heads are preferably of the same size and shape, these features adding further to the ease of manufacture.
-The heads and stems of the elements can be of a wide variety of shapes. Often, but not always, the elements are circular in cross section and symmetrical about an axis. The heads of the elements shown in FIGS. 2 and 7 are, for example, essentially spherical or globe shaped. These form a preferred class since they can be easily wormed on unheaded cylindrical stems (or rods) by simply melting the tends thereof (using an infrared source, jets of hot air or passing the article with unheaded elements under a heated object such as a metal bar) and then cooling them. Another advantage of the articles having elements with globe-shaped heads is that they ordinarily can undergo many engagement and disengagement cycles without undue wear.
Another preferred head shape is illustrated in FIG. 3 wherein the heads are essentially bullet shaped. The force required to disengage these articles is substantially greater than the force required to engage them. Thus they are illustrative of another important and novel subclass in which the maximum angle between the axis and the bearing surface of each element during engagement is substantially less than the maximum angle between the axis and the bearing surface of each element during disengagement, the angles being measured within the element heads, so that the force required to disengage the articles is substantially greater than the force required to engage them.
The fasteners of this invention can be fabricated by known techniques such as injection molding, compression molding, extrusion, progressive stamping and die forming, casting, investment molding, embossing, vacuum forming, flocking, etc.
The unordered positions of the elements can be determined either during manufacture or prior thereto. They can be determined during manufacture, for example, by flocking rods without heads onto a base sheet and aflixing them thereto (e.g. by having the base sheet in molten condition at the time of flocking, by using a strong, permanent adhesive, etc.). Each rod is sufficiently long so that its volume is equal to the volume of the headed cam element to be made from it. Using vibratory flocking techniques, the rods are oriented substantially perpendicular to the base but in unordered positions. In a subsequent operation, the rods can be formed into headed cam elements, as described elsewhere herein. Alternatively, stems with enlarged heads on both ends can be flocked onto a base and affixed thereto (and the head adjacent the base can be buried if desired by a heavy adhesive coat).
If, during the flocking operation, the rods or headed stems are constrained so that each becomes affixed to a limited base area, then the positions of the elements will be unordered, with limitations, in two dimensions. If rods or headed stems of varying lengths and/or diameters are used which will form cam elements whose heads are located at various heights, then the heads of the elements will be located at unordered positions (heights) above the base (see FIG. 7) and will be unordered in three dimensions.
It is sometimes desirable to use a mixture of rods of different materials to flock onto a base, e.g. when rods of varying diameters are to be attached to the base and then headed (since if all were of the same material, those of smaller diameters would tend to form heads more quickly than those of larger diameters).
The pattern of elements in unordered positions can be also determined before manufacture of the fasteners. The articles with unheaded stems can be formed continuously, for example, on the surface of a die roll (which carries an unordered pattern of holes for the formation of unheaded stems or rods). In a subsequent operation, heads can be formed on the stems by melting the ends thereof as previously described, or by pressing the ends of the stems in to heated forming dies to form and shape the heads, cooling the dies to solidify the heads and then withdrawing them from the dies. The latter technique is used where particular shapes of heads (such as bullet shaped heads), which will not normally form by unconstrained melting, are desired. The individual fastener articles are then cut from the continuous web. Alternatively, a base sheet carrying the unheaded rods can be formed in an injection mold and the headed elements formed as previously described. In some cases the elements are formed so that the stems and portions of the corresponding heads are hollow. Regardless of how the articles of the invention are formed, there is ordinarily no repetition of the unordered pattern in a single final article. In any case, the particular advantages of the unordered pattern (such as the ability to engage complementary articles without regard to careful alignment) are realized.
Unordered element patterns can be formed in various ways. In one technique a large number of cylindrical disks of varying diameters with holes through the centers of the circular flat sides thereof are utilized (each disk representing one headed element and a surrounding space which is associated with it in two dimensions). The relative diameters of the disks may vary only a few percent or the ratio thereof may be as high as 3 to 1 or even higher. Any convenient thickness of the disks can be used which will allow them to be pressed together without overlapping. The disks are mixed together, tumbled randomly onto a piece of graph paper (usually rectangular coordinate graph paper) and turned so that one circular side of each is against the graph paper. The disks in this field are then pressed together from the edges (although usually not shaken or jogged to obtain maximum packing) and marks are made on the graph paper through the center holes. Preferably no marks are made through the center holes of the disks near the edges of the field (e.g. those on the edges or one removed therefrom) to avoid edge effects. The resulting pattern of marks on the graph paper represents elements located at unordered positions, limited by a minimum distance between positions, since element centers cannot be closer than when two of the smallest cylinders adjoin. This pattern of holes, usually at a reduced scale, can be used to form the pattern of holes in the stem forming roll or injection mold. Depending on the depth of the holes, the stems may be all of the same length or may vary according to some mathematical rule. In this instance, order will exist in the third dimension (height). However, in the other two dimensions, the positions are unordered, and the fasteners can be engaged without regard to careful alignment. If the stems are made so that the lengths, or diameters, vary without order, the heads of the elements will be located at unordered positions in three dimensions. Alternatively, the lengths or diameters of the stems can be related to particular sizes of the cylinders used to make the pattern.
By a modification of this method, ordered sub-groups of elements can be located at unordered positions, e.g. the cylinders are first arranged into ordered sub-groups by afiixing them to small sheets of paper. A number of these ordered sub-groups are placed in unordered positions and then used to form a pattern of holes in the same fashion as individual cylinders were used in the preceding description. A pattern formed in this manner is shown in FIG. 4, the centers of the elements in each triangular sub-group being shown connected by dashed lines for purposes of illustration. Sub-groups having other ordered arrays, for example, square, rectangular, circular, regular polygonal or irregular configurations, may be used. Sub-groups of different ordered arrays (ife. not having identical configurations) may be mixed together and adjoin or overlay each other.
Unorder can also be introduced into the articles of the invention by forming the element heads off center With respect to the stems and/or making them non-symmetrical. This oan be done by using heading dies which register off center from the elements to be headed or by heating a non-symmetrical unheaded stem from the top. If this non-symmetry of the heads is unordered from element to element, articles of the invention will be formed, even though the elements are attached to the base at ordered positions.
Die holes for the non-symmetrical stems can be formed using the electro discharge machinery technique in which the drilling tool does not rotate. Thus, the hole which is drilled has the same shape as the tool, which can, for example, be a cylinder the end of which is a plane at an acute angle to the axis of the cylinder. The tool is positioned for drilling so that the orientation of the angle at the end of the cylinder corresponds to the orientation of a directional vector for each point location (determined randomly, for example, by spinning a pivoted arrow for each hole). Articles molded using the resulting die have unheaded rods or stems of the same shape as the drilling tool but randomly oriented. Headed elements formed by heating these rods from the ends will be unsymmetrical and unordered with respect to one another. Heads of varying sizes and shapes can be made on the same fasteners by drilling the holes in the die With tools having varying diameters and end planes at varying angles with respect to the cylinder axis.
The articles of the invention are preferably of thermoplastic or thermosetting polymers such as polyethylene, polypropylene, nylons, melamine, polystyrenes, polycarbonates, various fluorinated polymers, epoxy resin, cellulose acetate, vinyl chloride polymers, copolymers of the above and other materials, modified polymers including filled and plasticized polymers, etc.; although they may in certain cases also be of metals, ceramics, glasses, fibrous products such as papers, resin bonded fibrous sheeting, laminated sheets, glass filament reinforced webs, etc. The actual material which is chosen for a particular application depends upon such factors as suitability to fabrication in the desired configuration, projected ambient conditions of use (heat, moisture, acidic or basic conditions, etc.), mechanical conditions of use (tensile, and elastic stresses, repeated flexing), etc. In some cases, it is desirable to place the articles in the location of intended use and even to engage them when the material of construction is at an intermediate stage, for example, as a partially cured polymer or as a green ceramic and then bring the material to its final stage, e.g. by curing.
The versatility of the articles of the invention with respect to function as well as materials of construction render them widely useful. Panels orh'angings can be attached to walls with great ease, invisi'bly and, if desired with great tenacity. Adverse conditions of temperature, humidity, chemical corrosion, dirt, grease, etc. are of comparatively little concern. Depending upon the design and the particular elastic material which is used, the articles of the invention can be usable once, several times or many times. In certain articles of the invention disengagement can be accomplished only by forces suflicient to destroy the functional surf-aces by tension or shear, these articles being intended to hold permanently. The functional surfaces can be carried on the flat or curverlsurfaces of variously shaped articles, e.g. on sheets, spheres, cylinders, cubes, etc. and a single unitary article can have a plurality of functional surfaces thereon.
Various polymeric systems can be used in conjunction with the articles of the invention. Thus, for example, the base surface between the contour elements of the functional surface can be coated to any desired depth with a liquid or partially cured semisolid polymeric system, the surface engaged with another functional surface and the polymer thereafter activated and/ or cured. Some types of systems which can be used in this way are cements (which can be subsequently dried), sealants (which can be subsequently set), foaming systems (which can be subsequently foamed) and cross linking polymers (which can be subsequently cross linked).
The contour elements of the invention vary greatly in size and proportions, the actual limits depending largely upon the ease and efficiency of production and the intended use. Ordinarily, for ease of fabrication, handling, storage and use the elements are from about 0.025 to 1 inch in length and the length to diameter ratios of the stem portions thereof are from about 0.5 to
For definitions of terms herein relating to strength of materials, reference is made to the book Formulas for Stress and Strain by R. J. Roark, McGraw-Hill Book Company, Inc., 1943, especially at pages 5-12.
What is claimed is:
1. A fastener comprising a complementary pair of unitary interengaging articles, each having a relatively stitf base from which emanates a multiplicity of resilient cam elements each comprised of a stem terminating in an enlarged shaped head, in which (1) the position of each element head is unordered with respect to the positions of the other element heads (2) a substantial number of pairs of adjacent element heads over the surface are spaced so that the distance between the heads is greater than the stem diameter (3) ordinarily three or more adjacent element heads lie along curved paths and (4) when the complementary articles are interengaged, a majority of the element heads of each article are held beneath the element heads of the other article.
2. A fastener according to claim 1 wherein the element heads are globe shaped.
3. A fastener according to claim 1 wherein the element heads are unsymmetrically shaped.
4. A fastener comprising a complementary pair of unitary interengaging articles, each having a relatively stiff base from which emanates a multiplicity of resilient cam elements each comprised of a stem terminating in an enlarged shaped head, in which (1) the position of each element head is unordered with respect to the positions of the other element heads (2) a substantial 8 number of pairs of adjacent element heads over the surface are spaced so that the distance between the heads is greater than the stem diameter (3) ordinarily three or more adjacent element heads be along curved paths and (4) when the complementary articles are interengaged, a majority of the element heads of each article are held beneath the element heads of the other article, the maximum angles between the axes and the bearing surfaces of the elements during engagement being substantially less than the maximum angles between the axes and the bearing surfaces of the elements during disengagement, the angles being measured within the element heads, whereby the force required to disengage the articles is substantially greater than the force required to engage them.
5. A fastener according to claim 4 wherein the element heads are bullet-shaped.
6. A fastener comprising a complementary pair of unitary interengaging articles, each having a relatively stiff base from which emanates a multiplicity of resilient cam elements each comprised of a stem terminating in an enlarged shaped head, in which (1) the position of each element head is unordered with respect to the positions of the other element heads (2) a substantial number of pairs of adjacent element heads over the surface are spaced so that the distance between the heads is greater than the stem diameter (3) ordinarily three or more adjacent element heads lie along curved paths and (4) when the complementary articles are interengaged, a majority of the element heads of each article are held beneath the element heads of the other article, the elements being of a uniform size and shape and each element being symmetrical about its central axis.
7. A fastener according to claim 6 wherein the element heads are globe shaped.
References Cited UNITED STATES PATENTS 2,499,898 3/ 1950 Anderson. 3,031,730 5/1962 Morin 24-204 3,101,517 8/1963 Fox 24-204 3,191,255 6/1965 Nealis 24-204 X 3,266,113 8/ 1966 Flanagan 24-204 FOREIGN PATENTS 815,072 9/ 1' Germany.
BERNARD A. GELAK, Primary Examiner.