Patent Publication Number: US-6209722-B1

Title: Tee-nut strip with edge membranes

Description:
This is a continuation of application Ser. No. 09/190,621 filed Nov. 12, 1998 now U.S. Pat. No. 5,918,738. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to fasteners known as Tee-nuts, which are formed into a strip by means of a flexible membrane secured to the Tee-nuts. 
     BACKGROUND OF THE INVENTION 
     Tee-nut fastening devices are widely used in many industries, in particular in the furniture industry. They consist of a sheet metal member having a sleeve with internal threads, and flanges around one end of the sleeve and spikes formed at right angles to the flanges which are embedded in the workpiece around a pre-drilled hole. 
     They are widely used for constructing furniture items such as bookshelves, cupboards, chairs, beds and the like, and in many other situations. Various forms of high-speed insertion machines have been devised, by means of which the Tee-nuts may be driven into a workpiece. Usually there is a pre-drilled hole in which the sleeve is received, and the flange lies on the surface of the workpiece with the spikes embedded in it, thereby holding the entire Tee-nut in position. Modified forms of Tee-nuts are available which are flared out at the free ends of the sleeves so as to provide a more secure hold in the workpiece. Other forms of Tee-nuts are available which are formed with sleeves capable of punching their own hole through the workpiece. 
     The rapidity and repetition rate of the insertion of such Tee-nuts into a workpiece is a significant cost factor in the production of the end product. In the past, insertion machines have been provided with hoppers. The Tee-nuts were simply dumped loose in the hopper, and the hopper vibrated, to separate the Tee-nuts and cause them to enter a feedslide. The feedslide supplied the Tee-nuts, one after another, to the punch. 
     These systems were not always reliable and in some cases the hoppers became jammed with Tee-nuts and in other cases the feedslide became jammed because the Tee-nuts would not slide down the feedslide. 
     Various examples of such Tee-nut setting machines are shown, one example being shown for example in U.S. Pat. No. 3,460,217. A modified form of Tee-nut machine in which the Tee-nuts were driven upwardly into the workpiece is shown in U.S. Pat. No. 4,821,940. The problem with these systems involving loose Tee-nuts is that the slide would feed the Tee-nuts to a feed mechanism which would then deliver them one at a time to a plunger or punch. This was relatively complex and costly, and was not always reliable, at the speeds of operation which are required. 
     With a view to overcoming many of these disadvantages and with a view to providing a much simpler machine, a Tee-nut inserting machine was devised, for receiving Tee-nuts from a coil or roll. The Tee-nuts themselves were formed into a coil by means of a backing tape or membrane, or in some cases by means of welded wire filaments. Examples of such systems are shown in U.S. Pat. Nos. 4,214,843; 5,327,645; 5,299,686 and 5,214,843. 
     The machines and Tee-nut strips disclosed in these patents overcame the problems arising from placing loose Tee-nuts in a hopper, and then attempting to sort out the Tee-nuts and feed them one by one down a Tee-nut slide. 
     However, the formation of the Tee-nuts into a strip by means of a flexible membrane such as a tape was not always totally satisfactory. In some cases, the membrane, which might be for example, paper or the like, would simply break between the Tee-nuts. In other cases, the formation of the Tee-nut strips by means of welded wires was not always satisfactory due to the difficulties and complexities of forming high-speed spot welds. In both systems, when the insertion machines were operated at high speed there was a tendency for the Tee-nut strips to become broken or Tee-nuts to become separated from the strip. In both cases this would lead to a false insertion of a Tee-nut, i.e. there would be a hole in the workpiece with no Tee-nut, and this was unacceptable. 
     The first objective of the invention therefore is to provide an improved fastener strip such as a Tee-nut strip which is capable of high-speed operation with fastener insertion machines, whether of the type described or otherwise. 
     A further requirement which has developed more recently, is the provision of a portable fastener applicator for example for use with Tee-nuts, similar to the air pressure-operated nailing applicators which are in common use. 
     A portable hand-held fastener applicator would have many advantages over the stand-alone applicator machines. However, in order to operate, a satisfactory form of fastener strip must be provided for the portable hand-held fastener applicator. 
     BRIEF SUMMARY OF THE INVENTION 
     With a view to providing an improved fastener strip, for example a Tee-nut fastener strip, the invention provides a fastener strip for fasteners of the type having a grip portion and flanges, having a first side and a second side, formed at one end of the grip portion and the fastener strip comprises membrane means formed of flexible material and bonding means that bonds the membrane means to the first side of the flanges and to the second side of the flanges such that the membrane means grips the flanges on both the first and second sides of the flanges simultaneously. In particular, the fasteners are held in sequential relation along the membrane means. 
     In particular embodiments of the invention, the membrane means may be comprised of one or more membrane means as appropriate. 
     If four membrane means are provided, the first and second membrane means may be bonded on opposite sides of a first, or upper, side of the flanges, defining a linear spacing there between along the length of the centre of the fasteners, and the third and fourth membrane means may be bonded to a second, or under, side of the flanges, on opposite sides of said grip portion. In this case, it may be easier to apply the separate membrane means to the fasteners, such as Tee-nuts, easily and the central portion of the leading and trailing edge of each fastener is clear of obstruction. This improves the ease of preparing the fastener strips and the ability of the fastener strip to be reliably fed in a typical feed slide mechanism. 
     If two membrane means are provided, the first and second membrane means may be bonded to a first, or upper, side of the flanges, such that there is a spacing between the first and second membrane means, and then each of the first and second membrane means folded over and bonded to a second, or under, side of the flanges so that each of the first and second membrane means grip the flanges on both the first, or upper, side and the second, or under, side simultaneously. In this case, the central portion of the leading and trailing edge of each fastener is left clear of obstruction. This improves the ability of the fastener strip to be reliably fed in a typical feed slide mechanism. 
     If only one membrane means is provided, the membrane means may be bonded to a first, or upper, side of the flanges and then folded over and bonded to a second, or under, side of the flanges so that the membrane means grips the flanges on both the first, or upper, side and the second, or under, side simultaneously. 
     A further feature of the invention is that portions of the membrane means extending between the fasteners can be bonded directly to one another between said fasteners to form a double thickness laminate. 
     The membrane means can be of any suitable material such as paper, polypropylene tape, synthetic material such as thermoplastic strip materials and the like, and the bonding means can be any suitable adhesive. Alternatively, the membrane means may be extruded plastic material which is extruded hot directly onto the sides of the flanges of the fasteners and the bonding is provided by thermo-plastic adhesion. 
     It will be understood that the membrane means may comprise combinations of membrane web material, extruded plastic material, or other materials used together or individually on first, or upper, or second, or under, sides of the flanges. 
     It is preferrable that the membrane means be tearable between adjacent fasteners as they are inserted into the workpiece. It is also preferable that the membrane means be sufficiently flexible that the fastener strip can be rolled into a coil if desired. 
     A method of forming fasteners, for example Tee-nuts, into a strip using membrane means as described above is also a feature of the invention, and incorporates the steps of bonding the membrane means to a first side of the flanges on the fastener and bonding the membrane means to a second side of the flanges on the fastener so that the membrane means grips the flanges on both the first and the second sides simultaneously. 
     In particular embodiments of the invention, the method may include the use of one or more membrane means and may include steps of folding the membrane means, as appropriate, so that the membrane means grips the flanges on both the first and the second sides simultaneously. 
     In particular, the method may also include a step of indenting the membrane means between adjacent fasteners to bond the membrane means together to form a double thickness laminate. 
     Although Tee-nut fasteners and Tee-nut fastener strips are a principal application of the invention, the invention is applicable to any fasteners having flange portions which can be engaged by a membrane and for which the membrane can be bonded to two sides of the flange portions simultaneously. 
     The various features of novelty which characterize the invention are pointed out with more particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is an upper perspective illustration partially cut away showing a Tee-nut strip in accordance with a first embodiment of the invention; 
     FIG. 2 is a section along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a section along the line  3 — 3  of FIG. 1; 
     FIG. 4 is an upper perspective illustration partially cut away of another embodiment; 
     FIG. 5 is a section along the line  5 — 5  of FIG. 4; 
     FIG. 6 is a section along the line  6 — 6  of FIG. 4; 
     FIG. 7 is a perspective illustration of one form of feed mechanism showing the Tee-nut strip rolled into coil; 
     FIGS. 8A,  8 B and  8 C are schematic illustrations showing the step-wise formation of the Tee-nut strip in accordance with the embodiments of FIGS. 1 or  4 ; 
     FIG. 9 is a perspective illustration of a further embodiment of the Tee-nut strip according to the invention; 
     FIG. 10 is a section along the line  10 — 10  of FIG. 9; 
     FIG. 11 is a section along the line  11 — 11  of FIG. 9; 
     FIGS. 12A,  12 B and  12 C, are schematic illustrations corresponding to FIGS. 8A,  8 B and  8 C, showing the step wise formation of Tee-nut strips in accordance with further embodiments of the invention; and 
     FIG. 13 is a schematic side elevation of a strip forming production line, showing extrusion of thermo plastic material on both upper and under sides of said fasteners. 
    
    
     DESCRIPTION OF A SPECIFIC EMBODIMENT 
     Referring first of all to FIGS. 1,  2  and  3  the Tee-nut strip according to the invention will be seen to be comprised of a plurality of Tee-nuts indicated generally as  10 . Each of the Tee-nuts has a grip portion, in this case an internally threaded cylindrical sleeve  12 . At the upper end of the sleeves  12  there are formed flanges  14 — 14 . Prongs or spikes  16 — 16  extend downwardly from the flanges at right angles. 
     As explained above, the invention is of general application to forming various types of fasteners into a strip, although Tee-nuts are a typical example of fasteners which are suitable for this system and also troublesome to handle in other ways. However, the invention is not restricted solely to the application of Tee-nuts but comprehends all such fasteners as may be formed into a strip in this way. The use of the term “Tee-nuts” throughout is deemed to be generic to all such fasteners. 
     In order to form the Tee-nuts into a strip, a membrane means is applied to the first or upper surfaces of the flanges  14 — 14 . In this embodiment the membrane means comprises a continuous membrane strip  20 , in this case typically being formed of thin flexible thermo-plastic material. The membrane means may also be formed of polypropylene tape, paper, paper together with a laminate of thermo-plastic material or adhesive, or may simply be an extruded strip or strips of thermo-plastic material which is(are) extruded directly onto the Tee-nuts. In some cases it may be desirable to use a combination of the above, i.e. extruded membrane material on the upper surface of the flanges, and web material bonded on the under surface of the flanges. In this embodiment the membrane strip  20  has a width W 1  indicated by the chain dotted lines in FIG. 1, and the width W 1  is greater than the width W 2  defined by the edges of the two flanges  14 . In this way, the side edges indicated as  22 — 22  of the membrane  20  overlap on either side of the flanges  14 . During fabrication these side edges are folded over the ends of the flanges  14 — 14  of each nut  10 . The membrane  20  is formed typically with an adhesive surface indicated generally as  24  (FIGS.  2  and  3 ). In this way the main portion of the membrane  20  is adhesively bonded to the upper or first surfaces of the flanges  14 , and the folded over edge portions  22 — 22  are bonded to the underside or second surfaces of the flanges  14 — 14 . 
     During manufacture, the portions of the membrane  20  and folded edge portions  22  extending between adjacent Tee-nuts  10  will be pinched or squeezed as at  26 , so that in this way the upper and under portions of the membrane are bonded together to form a double thickness laminate membrane, which double thickness portion extends between adjacent Tee-nut flanges. 
     It will be observed that the Tee-nut flanges  14  are of what may be considered as generally octagonal shape, so that their side edges define angular spacings which will permit the squeezing of the membrane portions  26 — 26  between adjacent flanges  14 . This materially increases the strength and usefulness of the Tee-nut strip. 
     In another embodiment of the invention, as shown in FIGS. 4,  5  and  6 , the membrane means may comprise a pair of membrane strips  30 — 30 , which define a spacing S between them. The spacing S will register with the open upper ends of the internally threaded sleeves  12 . 
     As in the case of the FIG. 1 embodiment, the two membrane strips  30 — 30  will define folded over edge portions  32 — 32 , which are folded under the ends of the flanges  14  of the Tee-nuts. Between the Tee-nut flanges, indented portions  34  are formed, by squeezing the upper and under portions of the membrane strips together to form a double thickness laminate. 
     As explained, the Tee-nut strips may be used in various ways. For example they may be used simply coiled into a large coil and placed on a feed table as shown in FIG. 7, the coil being shown as  40  and the table being shown as  42 . In a typical case the strip as it is uncoiled off the coil  40  may be passed through a feed slide  44  which rotates the strip through a ninety degree rotation so as to place the Tee-nut barrels facing either vertically upwards (as shown) or vertically downwards (not shown) depending upon the design of the insertion machine. 
     Clearly the Tee-nut strips may also be used in other applications and in particular for example in portable Tee-nut applicators (not shown) which would be similar to power operated nailing applicators. The Tee-nut strip would then simply be fed in through a magazine slide (not shown) such as well known in the art relating to nailing applicators. 
     The formation of the strip is believed to be self-evident from the foregoing description, but is illustrated in step-wise form in the schematic drawings of FIGS. 8A,  8 B and  8 C. In FIG. 8A the Tee-nuts  10  are arranged into a continuous column in suitable feed mechanism indicated generally as  50 . 
     The membrane strip  20  is simply extended flat over the first or upper surfaces of the flanges  14 . 
     As shown in FIG. 8B the membrane  20  is then pressed down on flanges  14  and, as shown by the two arrows, the edge portions  22  are folded around the flanges  14 . 
     As shown in FIG. 8C the two folded portions  22  are then folded up underneath the under or second surfaces of the flanges  14  and bonded thereto. 
     The portions  26  or  34  are subjected to a squeezing or pinching action between adjacent Tee-nut flanges so as to form double thickness laminates. 
     Essentially the same operations would be carried out for the embodiment of FIGS. 4,  5  and  6 . 
     As illustrated in FIGS. 9,  10  and  11 , in another embodiment of the invention, the membrane means may comprise separate upper and under membrane strips indicated as  30 A and  32 A. The upper and under strips are separate from one another, and are simply bonded to the upper and under sides of the Tee-nut flanges, without the requirement for folding over the edges. 
     As illustrated in FIG. 11, between adjacent Tee-nuts, the two membranes  30 A and  32 A will be squeezed and laminated together. 
     It will also be appreciated that in some cases, as suggested above, the membrane means may be in the form of continuously extruded thermo-plastic material, which is extruded hot directly onto the upper and under surfaces of the Tee-nut flanges. Again, typically this material would be squeezed together to form a double thickness laminate in the gaps between the Tee-nut flanges as shown above. 
     In other cases, it may be possible to use a combination of extrusion of thermo-plastic, with a web membrane material. This is illustrated specifically in FIGS. 12A,  12 B and  12 C. In this case, extruder nozzles  60 — 60  would be positioned above the Tee-nut flanges  14  on the rails  50 . They would extrude continuous strips of hot thermo-plastic strip material indicated as  62 . This material would then be deposited on the upper surfaces of the Tee-nut flanges  14  where it would become bonded and chilled. 
     A similar extrusion operation could be carried out underneath the flanges. On the other hand, as illustrated in FIGS. 12A,  12 B and  12 C, continuous web material indicated as  64 — 64  may be bonded to the undersides of the flanges. In either case, the membrane means between the Tee-nut flanges will be squeezed together to form a double thickness laminate, in the same manner as shown above. 
     As shown in FIG. 13, the double extrusion operation described above is illustrated in side-elevational schematic form. The rails  50  carry the Tee-nut flanges  14 . 
     Upper extruder nozzles  60  would be positioned as shown in FIG. 12, and under extruder nozzles  66  would be located beneath the Tee-nut flanges. The extruder nozzles are located preferably close to the Tee-nut flanges, and once the line starts to operate, the strip material will extrude continuously, simultaneously from the nozzles  60  and  66  onto the upper and under sides of the Tee-nut flanges. 
     Preferably, rollers  68  and  70  are provided above and beneath the extruded thermo-plastic, so as to squeeze it firmly together against the upper and under sides of the Tee-nuts respectively, and at the same time, squeeze the upper and under strips of thermo plastic material  72  together between the flanges in the manner described above. 
     The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the scope of the appended claims.