Patent Publication Number: US-6907647-B2

Title: Eyelet for reinforcing the edge of a hole in a carrier strip and device for attaching an eyelet to a carrier strip

Description:
The invention pertains first to an eyelet of the type indicated in the introductory clause of claim  1 . There are two-part eyelets, the first part of which consists of an eyelet, the second consisting of a disk. These two parts are located on opposite sides of the carrier web and clamp the carrier web between them in sandwich-like fashion. 
   One-part eyelets are also known, however, which do not have a disk part and which thus consist only of an eyelet part (U.S. Pat. No. 2,107,375 A). Pleats are formed in the end of the neck of the eyelet part, as a result of which radial expansions are created between axial projections. When the eyelet part is flanged over, a C-shaped profile is formed between the neck and the plate, the radial expansions being supported against the rear surface of the carrier web. The carrier web thus extends radially into the interior of the C-shaped profile. This known eyelet has limited resistance to pull-out. 
   In connection with a single-part eyelet comprising of an eyelet collar with a semi-circular profile and an eyelet neck with uniformly circumferentially extending V-shaped cross-section on the end face of the neck, it is known (EP 0 673611 A1) to close the resulting C-shaped profile to such an extent that the carrier web is clamped in the remaining gap between the outer edge of the eyelet collar and the end face of the eyelet neck. The semi-circular interior of the eyelet collar is divided by a peripheral annular rib into an inner and an outer groove wherein the annular rib over portions thereof carries pointed tips. The transition area between the eyelet neck and the eyelet collar is provided with conical stabilizing ribs which prevent flanging of these areas. After flanging of the residual length of the neck, the end face of the eyelet neck is aligned only with the outer groove of the eyelet collar. In the interior of the C-shaped profile, a labyrinth for the carrier web is provided. The tips of the annular rib appear to effect a holding action securing the carrier web against rotation but the tearing-out stability of the carrier web is insufficient because the topside of the carrier web is contacted only by the outer edge of the eyelet collar and the bottom side of the carrier web is only contacted by the end face of the eyelet neck. 
   Moreover, for a single-part eyelet it is also known (DE 299 03 124 U1) to cut the free end of the neck in the flanging tool into individual tab-shaped securing elements and to bend them radially outwardly. For this purpose, the bottom part of the flanging tool is provided with a circular arrangement of widening depressions which are separated from one another by cutting edges that point toward the top part of the tool. After attachment to the carrier web, the securing elements form, viewed in cross-section, together with the eyelet disk a V-shaped folded product. The carrier web which is clamped between the legs of the V is secured only insufficiently in this folded product. 
   The invention is based, first, on the task of developing an inexpensive, quickly installable eyelet of the type indicated in the introductory clause of claim  1 , which, after it has been attached to the carrier web, is characterized by high resistance to tear-out. This is achieved according to the invention by the measures cited in claim  1 , to which the following meaning attaches: 
   In the invention, a ring-shaped profile is formed which extends across more that a complete circle because practically the entire length of the neck is rolled spirally into the interior of the ring-shaped profile when the neck is flanged over; the projections provided at the end of the neck are included in the formation of the spiral. As a result, special compression points, which provide very high resistance to the tensile stresses exerted on the carrier web, are produced on the gripped carrier web inside the spirally rolled-in ring-shaped profile. These compression points are formed because the projections on the spirally rolled-in ring-shaped, flanged-over neck press an area of the carrier web surrounding the hole against opposite support surfaces, which, in the case of the present ring-shaped profile, are formed by the plate or by the transition between the plate and the neck of the eyelet part. The carrier web adapts with a ring-segment shape to the ring-shaped profile and the rolled-in projections on the neck and is compressed in a sandwich-like fashion between the ring surfaces and the spiral surfaces. The carrier web extends beyond the compression points to the edge of the hole in the interior of the ring-shaped profile. The projections on the spirally shaped rolled-in end pieces of the neck point toward the interior of the ring-shaped profile and are oriented counter to the tensile loads occurring during use of the carrier web. In front of these real compression points a step-like increase of the web material takes place which upon stresses acting on the carrier web actually improve the grip at the compression points. The spiral rolling of the end piece of the neck provides a very clean riveting action without having to fear injuries being inflicted on the user. The eyelet according to the invention is much more resistant to pull-out than the state of the art indicated above. 
   In comparison with the much more complicated, two-part eyelets, the eyelet according to the invention provides a surprisingly high resistance to tear-out; it is, in fact, 30-75% stronger. This strength is obtained precisely in the case of the previously so difficult to handle flexible or stretchable carrier webs, which could not be processed at all with one-part eyelets in the past. Because of the one-piece design of the invention, the disk part is eliminated, which saves material, warehouse costs, freight costs, and handling during the installation process. Because the one-part eyelet part according to the invention can be installed rapidly, the cost of installing the eyelet is reduced. The neck of the eyelet part according to the invention must be long enough to make it possible for the desired ring-shaped profile to be obtained during the flanging operation. The thickness of the carrier web, of course, must also be taken into account. The only other step to be taken is to produce the axial or radial projections at the free end of the neck, which can be done in various ways. 
   One possibility is to form the projections by making radial holes in the tubular wall of the neck. When the neck is flanged over, these radial projections penetrate into the edge area of the material around the hole in the carrier web being gripped, where they dig themselves in and produce the compression points against the opposing support surface on the plate. The other possibility, namely, forming projections which proceed in the axial direction, is easier to manufacture, however. The pronged or wave-like terminal edge of the neck mentioned for this purpose in claim  2  is suitable. In this case, the entire edge of the neck has a continuous profile and does not, as in the state of the art mentioned above, show individual projections spaced a certain distance apart. When the ring-shaped profile is formed, both the neck and its projections are deformed jointly according to the invention. When the ring-shaped profile is produced during the flanging-over operation, the prong digs into the web material, and there is therefore not just a clamping effect between the prong and the opposing support surface of the plate but also a positive connection, which is established between the prong and the carrier web. The greater the tensile force exerted on the carrier web, the greater the strength with which the prongs dig into the web. This explains the surprisingly high resistance of the eyelet according to the invention to tear-out. 
   The invention also pertains to a device for installing the eyelet according to the invention. In the case of the known device (U.S. Pat. No. 1,838,973 A), which is intended for two-part eyelets, the thrust ring in the lower tool projects beyond the cutting edge provided here. The upper tool has an axially movable, central insert with a bore; this insert projects out axially beyond the adjacent surfaces of the upper tool. During the working stroke of the two tools, the carrier web is pushed by the central insert of the upper tool into the thrust ring before the central insert meets the cutting edge of the lower tool to cut the hole in the carrier web. The attachment of the carrier web to this two-part eyelet, which consists of both an eyelet part and the previously mentioned disk part, is therefore unattractive, because folds are formed in the carrier web. 
   The invention is therefore also based on the task of developing a device which can be used to attach the one-part eyelet cited in claim  1  more attractively to the carrier web and with greater resistance to tear-out. This is accomplished according to the invention by the features cited in the characterizing clause of claim  9 , to which the following special meaning attaches: 
   In the invention, the upper tool is provided with a counter-thrust ring to work together with the thrust ring in the lower tool, the counter-thrust ring being subjected to a force acting toward the lower tool. It is recommended here, in accordance with claim  10 , that these two rings be provided with opposing beveled surfaces. When the two tools perform their stroke, the carrier web is tensioned between the two rings, and the beveled surfaces exert an additional stretching and smoothing-out effect on the carrier web. During the following flanging operation of the one-part eyelet, the carrier web is kept flat and smooth, which ensures that the eyelet is attached ideally to the carrier web. The tensioning of the web minimizes the amount of material which is pulled into the eyelet. This has the result that spacing of the eyelets can be maintained with precision, and positional deviations can be limited even in the case of large tarps. 

   
     Additional measures and advantages of the invention can be derived from the subclaims, from the following description, and from the drawings. The drawings illustrate the invention on the basis of an exemplary embodiment: 
       FIGS. 1 and 2  show top views of the visible side and the rear surface, respectively, of a carrier web equipped with an eyelet according to the invention; 
       FIG. 3  shows a greatly enlarged cross section through the installed eyelet according to  FIG. 1  along the cross-sectional line III—III in  FIG. 1 ; 
       FIG. 4  shows an axial cross section through the special eyelet part of the diskless eyelet according to the invention in the original state, that is, before it has been installed in the carrier web; 
       FIG. 5  shows an enlarged, flattened view of part of the edge area of the eyelet part according to the invention, namely, the area indicated by the “V” in  FIG. 4 ; and 
       FIG. 6  shows an axial half-cross section of the parts of a two-part device according to the invention for installing the eyelet part shown in  FIG. 4 , the upper tool being at the top end of its stroke with respect to the lower tool. 
   

   As  FIGS. 1 and 2  show, an eyelet is to be used to reinforce the edge area  21  around a hole  22 , which has been cut in a carrier web  20 . The carrier web  20  is usually a flexible and possibly stretchable material such as an automobile tarp. According to the invention, the hole is reinforced with a one-piece eyelet part  10 . In  FIGS. 4 and 5 , the eyelet part  10  is shown in its original state, before installation.  FIGS. 1 ,  2 , and  3 , however, show the eyelet part  10 ′ after installation, in its final state in which it is exercising its hole-reinforcing function. 
   As  FIGS. 1 and 2  show, an eyelet is to be used to reinforce the edge area  21  around a hole  22 , which has been cut in a carrier web  20 . The carrier web  20  is usually a flexible and possibly stretchable material such as an automobile tarp. According to the invention, the hole is reinforced with a one-piece eyelet part  10 . In  FIGS. 4 and 5 , the eyelet part  10  is shown in its original state, before installation.  FIGS. 1 ,  2 , and  3 , however, show the eyelet part  10 ′ after installation, in its final state in which it is exercising its hole-reinforcing function. 
   The eyelet part  10  can be divided into a plate  11  with a curved cross section, extending essentially in the radial direction, and a tubular neck  12 , extending in the axial direction. To increase the dimensional stability of the eyelet and to make it easier to flange over the neck  12  into a ring, as will be described in greater detail below, the plate  11  is provided with a curved profile  13 . As a result, an especially conspicuous arc-shaped transition  14  is obtained between the plate  11  and the neck  12 . The neck is provided at its free end  15  with axial projections  16 , which, therefore, extend in the direction of the neck  12 . These projections consist in the present case of a curved, pronged terminal edge  17 , as can be seen in FIG.  5 . This edge has the following appearance. 
   The tips  17  of the prongs are provided with convexly rounded areas  27 , whereas the gaps  18  between the prongs have concavely rounded areas  28 . As a result, the pronged profile  19  acquires a wave-like form. The course of the waves is asymmetric. That is, the radius of curvature of the rounded areas  27  of the prong tips  17  is smaller than that of the rounded areas  28  of the gaps between the prongs. 
   This eyelet part  17  is attached to the carrier web  20  by the device  30 , shown in FIG.  6 . The device  30  consists of essentially five parts, which are able to move in the axial direction with respect to each other in a chronological sequence. These parts include, first, the bottom tool  32 , which, in the present case, remains at rest and which carries a thrust ring  34 , which is able to move passively in the axial direction with respect to the lower tool. In addition, the device  30  also includes an upper tool  31 , which is able to move actively with respect to the lower tool  32  and which has a central, coaxial insert  33 . This insert is also able to move passively in the axial direction with respect to the upper tool  31 . Finally, the upper tool  31  is enclosed circumferentially by a counter-thrust ring  54 , which is also able to move passively in the axial direction. The central insert  33  and the counter-thrust ring  54  are subjected to load in the direction of the force arrows  35  and  55  toward the lower tool  32 , whereas the thrust ring  34  in the lower tool  32 , in mirror-image fashion, is acted upon by a group of springs  56  acting in the direction of the force arrow  36  toward the upper tool  31 , these springs being installed in axial holes in the bottom tool  32 . The springs  56  are designed as helical springs, and pins  57  seated on the thrust ring  34  fit into the interior of the helical turns. The tool assembly  31 ,  33 ,  54  on the one side and the tool assembly  32 ,  34  on the other are able to move up and down with respect to each other, as indicated by the motion arrow  37  of the upper tool assembly  31 ,  33 ,  54 . 
   The counter-thrust ring  54  is guided on the circumferential surface  63  of the upper tool  31 . The force  55  exerted by the counter-thrust ring  54  is produced by a compression spring  64 , which is supported between a flank of a circumferential flange  65  on the upper tool  31  and the contact surface of a cutaway portion  66  of the counter-thrust ring  54 . The extent to which the counter-thrust ring  54  extends outward is determined by end stops. These consist in the present case of the heads  67  of a group of guide rods  68 , the length of which can be adjusted by the use of a threaded section  69  and a lock nut  71 . When in the resting state, the head  67  of the rod is supported on the top surface of the flange  65 . As a result, the desired extension  70  of the counter-thrust ring  54  relative to the upper tool  31  is determined. 
     FIG. 6 , as already mentioned, shows the device at the upper reversal point of its stroke  37 , at which the maximum distance  38  is present between the upper tool  31  and the lower tool  32 . As a result, an eyelet part  10  can be conveniently inserted into the receiving profile of the upper tool  31  and around the central insert  33 . For this purpose, the upper tool  31  has a receptacle  39 , which conforms to the profile of the plate  11 . The area provided with the receptacle  39  is subject to wear during normal use. To facilitate the renewal of a worn-out device  30 , therefore, the lower part of the upper tool is provided with an insert  31 ′, which is detachably connected to the upper part of the upper tool  31  by suitable means such as the screw shown in the drawing or the like. This insert  31 ′ carries the receptacle  39 . 
   After the eyelet part  10  has been inserted, the end of the neck  20  is supported on the circumferential surface of the central insert  33 . The central insert  33  is provided with a flat end surface  43 . To secure the eyelet part in position in the tools  31 ,  33 , a retaining element  44 , which, in the present case, consists of a radially spring-loaded pin, is used, which is located in the circumferential area of the central insert  33 . 
   The carrier web  20  is laid between the two tool parts  31 ,  32 ; at this point, the web is still unperforated. The previously mentioned springs  56  hold the thrust ring  34  in a defined starting position, shown in FIG.  6 . At maximum stroke of the tool, the defining-upper surface  45  of the thrust ring  34  is located above or preferably at the same level as a cutting edge  42  provided on the cutting tool  32 . As a result, a horizontal support plane  60  for the carrier web  20 , illustrated in broken line in  FIG. 6 , is created at the thrust ring  34 . 
   During the downstroke  37  of the upper tool assembly  31 ,  33 ,  54 , the leading counter-thrust ring  54  makes contact first with the carrier web  20  lying on top of the thrust ring  34 . The two rings  34 ,  54  are provided with bevels  58 ,  59 , which are essentially parallel to each other and which grip the carrier web  20  between them, as a result of which the carrier web  20  is initially put under a certain amount of tension. The bevel  58  of the thrust ring  34  forms an acute angle  61  to the support plane  60 , shown in dash-dot line in  FIG. 6 , which plane is determined by the end surface  45  of the thrust ring  34  serving to support the carrier web  20 . The counter-thrust surface  59  of the thrust ring  54  just mentioned is essentially parallel to the thrust surface  58 . When the two tools  31 ,  32  are moved toward each other  37 , therefore, the carrier web  20  is pulled over the edge  62 , which is formed between the end surface  45  and the bevel  58  of the thrust ring  34 . As a result, the carrier web is drawn flat in the area  29  to be punched. The carrier web  20  thus assumes a stretched-out condition in the support plane  60  mentioned. 
   Then the central insert  33 , under the force being exerted by the press plunger, makes contact with the upward-facing, visible side  23  of the carrier web  20 , thus pressing it against the cutting edge  42  of the lower tool  32 , which is resting against the bottom surface  24  of the carrier web. As a result, a circular hole is punched out of the carrier web  20 . The radius  46  of the hole determined by the cutting edge  42  is smaller than the radius  26  of the neck  12  of the eyelet indicated at  26  in FIG.  6 . 
   When the upper tool  31  is lowered further in the direction of the stroke arrow  37 , the carrier web  20  is pulled even tighter between two bevels  58 ,  59  of the two rings  34 ,  54 . The neck  12  of the eyelet part  10  continues to pass through the hole thus formed and into the lower tool until the plate  11  of the eyelet part  10  arrives at the thrust ring  34 , the carrier web  20  ending up between the plate and the ring. During this downward movement  37 , the upper tool  31  overcomes the elastic force  36  being exerted from underneath by the thrust ring  34 , and the neck  12  of the eyelet and its axial projections  16  are flanged over against the flanging profile  47  of the lower tool  32 . The elastic force  54  of the thrust ring  34  acting from above is weaker than the ejection force  36  acting from below on the thrust ring  34 . As in the case of the upper tool  31 , the lower tool  32  also has an insert  32 ′, positioned in the axial area, which carries the defining flanging-over profile  47 . This flanging-over profile  47  wears out after prolonged use. At that point, it necessary merely to replace this insert  32 ′. 
   During the flanging operation, the special riveting relationships shown in  FIG. 3  are obtained. Practically the entire length  48  of the neck of the eyelet part shown in  FIG. 4  is rolled up into a ring-shaped profile  50 , shown in  FIG. 3 , on the rear surface  24  of the carrier web  20 . The neck projections  16  are rolled up inside this ring-shaped formation  50 . These neck projections  16  are pressed against an opposing support surface  49 , provided by the previously described curved section  13  of the plate  11 ; the previously mentioned area  21  of the carrier web  20  situated around the edge of the hole as indicated in  FIG. 6  ends up between the projections and the opposing support. As a result, the compression points  40 , which proceed around the plate in a ring-like manner, are obtained, as can be seen in FIG.  3 . The end part  41  of the carrier web  20  continues into the interior  51  of the ring-shaped profile, conforming to the profile  50  and thus acquiring the form of a segment of a ring. The bevels  58 ,  59  continue to hold the carrier web firmly in place while the end part  41  is being rolled up during the riveting process. 
   When the eyelet part installed on the carrier web  20  is properly used, the tensile forces indicated by the force arrows  52  in  FIGS. 1-3  will occur. These tensile stresses  52  are absorbed at the compression points  40 . First, a clamping action between the neck projections  16  and the opposing support surface  49  is present at the compression points  40 . There is also a positive interconnection because of the profiling  19  of these projections  16 , as described above. That is, the tips  17  of the prongs dig into the web material, but, because of the rounded areas  27 ,  28  of the pronged edge  19 , the web  20  is not torn. A notch effect is thus avoided. On the other side of these compression points  40 , as designated at  53  in  FIG. 3 , the web becomes thicker again in front of the prong tips and also in the curved gaps  18  between the prongs. That is, the web  40  tries to return to its original thickness  25  at  53 . Under the tensile stresses  52  on the web  20 , the wave-like edges of the neck projections  16  dig into these step-like areas of increased thickness  53  of the web material  20 . The positive interlocking is thus improved even more, and the eyelet part  10 ′ riveted into the web  20  thus acquires a surprisingly high degree of tensile strength. 
   LIST OF REFERENCE NUMBERS 
   
       
         10  eyelet part (original state,  FIG. 4 ) 
         10 ′ riveted state of  10  ( FIGS. 1-3 ) 
         11  plate of  10   
         12  neck of  10 , eyelet neck 
         13  curved profile of  11   
         14  arc-shaped transition between  11  and  12   
         15  end part of  12   
         16  axial projection of the neck at  15  ( FIG. 4 ) 
         17  tip of prong ( FIG. 5 ) 
         18  gap between prongs 
         19  pronged edge at  15  ( FIG. 5 ) 
         20  carrier web 
         21  area at edge of hole in  20   
         22  hole in  20   
         23  visible side of  20   
         24  rear surface of  20   
         25  web thickness of  20  ( FIG. 6 ) 
         26  radius of neck  12  ( FIG. 6 ) 
         27  convexly rounded area of  17  ( FIG. 5 ) 
         28  concavely rounded area of  18  ( FIG. 5 ) 
         29  hole punching from  20  ( FIG. 6 ) 
         30  device 
         31  upper tool of  30   
         31 ′ replaceable insert in  31   
         32  lower tool of  30   
         32 ′ replaceable insert in  32   
         33  central insert in  31   
         34  thrust ring in  33   
         35  force arrow of  33   
         36  arrow of the elastic force of  34   
         37  stroke arrow of  31  with respect to  32  ( FIG. 6 ) 
         38  maximum stroke between  31  and  32   
         39  receptacle in  31  for  11   
         40  compression point of  20  between  16  and  49  ( FIG. 3 ) 
         41  end part of  20  on the other side of  40  ( FIG. 3 ) 
         42  cutting edge of  32   
         43  flat end surface of  33  ( FIG. 6 ) 
         44  retaining element for  10  at  33  ( FIG. 6 ) 
         45  end surface for  20  on  34   
         46  radius of hole  29  ( FIG. 6 ) 
         47  flanging profile of  32  ( FIG. 6 ) 
         48  length of neck  12  ( FIG. 4 ) 
         49  opposing support surface on  11  for  16  ( FIG. 3 ) 
         50  ring-shaped profile of  12  at  10 ′ ( FIG. 3 ) 
         51  interior of the ring-shaped profile of  50  ( FIG. 4 ) 
         52  arrow of the tensile force on  20   
         53  step-like increase in the thickness of  20  behind  40  ( FIG. 3 ) 
         54  counter-thrust ring 
         55  force of  54   
         56  spring for  36   
         57  pin on  34  for  56   
         58  bevel of  34 , beveled surface 
         59  counter-bevel of  54 , counter-beveled surface 
         60  support plane 
         61  angle of  58  with respect to  45   
         62  edge between  45  and  58  of  34   
         63  circumferential surface of  31   
         64  compression spring 
         65  flange 
         66  cutaway area 
         67  head of  68   
         68  guide rod 
         69  threaded engagement 
         70  extension 
         71  lock nut