Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to cold-formed machine bolts and, in particular, methods and tooling for economically producing such machine bolts. 
       PRIOR ART 
       [0002]    Machine bolts are commonly made by producing a headed blank or preform in a progressive cold-forming or forging machine and, thereafter, rolling a thread on the shank of the blank. Typically, the shank end of the blank is chamfered so that when finished, the threaded bolt has a “point”, albeit blunt, that enables it to be self-centering with a threaded hole and thereby facilitate its final assembly. 
         [0003]    Conventionally, the cold-forming process can involve five progressive forming stations. Typically, the tooling for shaping at least the shank part of the blanks is dependent on the length of a bolt. Thus, the prior art number of forming stations and the use of length specific tooling makes the tooling for a full range of bolt lengths relatively expensive for a bolt manufacturer. Consequently, to limit tooling costs, it is not unusual for a manufacturer to produce only a limited number of bolt lengths for a given bolt size (diameter). As a result, the manufacturer may not achieve the greatest economy and a bolt distributor or high volume user may have to depend on more than one manufacturer to supply its needs. Frequently, the cold-forming tooling available to a manufacturer may be incapable of pointing the blank so that a second machining operation is required and attendant material, machine time and labor costs are incurred. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention provides an exceptionally versatile tooling package for progressive forming machines capable of producing blanks for a full range of bolt lengths, all pointed, in four die stations. The number of tools or dies is greatly reduced compared to prior art practices, and can be applied to a four station header to produce a full range of pointed bolt lengths. This feat, which greatly reduces the number of tools, is accomplished in part by use of different fillers and/or a multi-position blank head supporting sleeve to axially position a tool or tools each at an appropriate one of multiple locations and thereby account for different blank lengths. More specifically, a complete set of forming tools can comprise a progressive series of cavities for forming and supporting the blank head and groups of tools for shaping the shanks of threaded to the head blanks or blanks with partially threaded shanks. 
         [0005]    The ability to use a four station machine, as afforded by the invention, rather than a five station machine, represents a significant reduction in tooling. Moreover, the disclosed methodology permits the use of some of the same tools to make hex flange bolts, hex head bolts, and socket head cap screws, thereby affording significant additional savings in tooling costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a cross-sectional view taken in a horizontal plane of a four station progressive cold-forging machine set up to make short threaded to the head hex flange bolts; 
           [0007]      FIG. 2  is a cross-sectional view taken in a horizontal plane of a four station progressive cold-forging machine set up to make long partially threaded hex flange bolts; 
           [0008]      FIG. 3  is a is a cross-sectional view taken in a horizontal plane of a four station progressive cold-forging machine set up to make full thread hex head bolts; 
           [0009]      FIG. 4  is a cross-sectional view taken in a horizontal plane of a four station progressive cold-forging machine set up to make partially threaded hex head bolts; 
           [0010]      FIG. 5  is a cross-sectional view taken in a horizontal plane of a four station progressive cold-forging machine set up to make short threaded to the head socket head cap screws; 
           [0011]      FIGS. 6   a - i  are a series of partial sections of the third station of the forging machine set up to point blanks of different lengths in the process shown in  FIG. 2 ; 
           [0012]      FIG. 7  is an exploded perspective view of a multi-position bolt head supporting sleeve and associated case and keys of the invention; 
           [0013]      FIG. 8  is a fragmentary cross-sectional view of the fourth station of the machine depicted in  FIG. 1 , taken in a vertical plane, set up for pointing relatively short, threaded to the head hex flange head bolts; 
           [0014]      FIG. 9  is a view similar to  FIG. 8  showing a set up for extruding the roll diameter of relatively long partially threaded hex flange head bolts; and 
           [0015]      FIG. 10  is an exploded perspective view of a hard plate and case assembly constructed in accordance with the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0016]    A cold forging machine  10  of generally conventional construction is represented by a die breast  11  and a slide  12  in  FIGS. 1-5 . The illustrated machine  10  has and the disclosed bolt forming processes uses four part forming or work stations  13 - 16 . In  FIGS. 1-5 , the slide or ram  12  is shown in its forwardmost position where the opposed faces of the punch and die cases can be as close as 1 mm. 
         [0017]    As mentioned above and explained in greater detail below, the invention offers a methodology for forming several popular styles of bolts in standard lengths, pointed and ready to be roll threaded, with a greatly reduced number of tools compared to that of previously used conventional methods. It will be understood that the tooling and process disclosed herein produce pointed bolt preforms or blanks that are subsequently finished in thread rolling dies, known in the art. These bolt preforms or blanks, as is customary in the industry, are sometimes simply called bolts herein, and this term is likewise applied herein to the parts being progressively formed. 
         [0018]    In the following written disclosure and drawings, like parts are identified with the same numerals. With reference to  FIG. 1 , the machine  10  receives wire stock  18  at a cut off station  19  where, during each cycle of the slide  12 , a precise length of material  26 , hereinafter referred to as a bolt, is severed by a pair of shear plates  22 ,  23 . A transfer of known design moves the bolt  26  from the cut off station  19  to the successive work stations  13 - 16 , each time the slide  12  reciprocates. 
         [0019]      FIG. 1  illustrates the progressive formation of pointed and eventually threaded to the head hex flange head bolts that, when rolled with a thread, can conform to the European standard DIN EN 1662, for example. When a bolt is removed from the last station in any of the bolt types disclosed herein, it will be finish headed, pointed, and ready for roll threading on a roll diameter on its shank. 
         [0020]    When the slide or ram  12  is retracted from its illustrated position, the bolt  26  is transferred to the first station  13 , it being understood that any preceding bolts in the first and subsequent stations  14 - 16  are simultaneously indexed or transferred to the next station and eventually discharged after forming in the fourth or last station  16 . 
         [0021]    The bolt  26 , in the sequence depicted in  FIG. 1 , has its shank portion received in a die or insert tool  27  on the die breast  11  and its head portion initially upset in an insert tool  28  on the slide  12  at the first station  13 . The diameter of the wire supplied to the cut off station  19  is substantially equal to, i.e. slightly smaller, e.g. a few thousandths of an inch, than the ideal or nominal roll or pitch diameter of a finished shank to account for any incidental growth in diameter in the first station  13  and subsequent stations  14 - 16 . The nominal roll diameter at the first station  13  and subsequent stations  14 - 16  exists along the full length of the shank so that the part can be of the threaded to the head style of fastener. 
         [0022]    The bolt  26  is transferred to the second work station  14  during the next machine cycle. Here, a hex shape is extruded on the head of the bolt  26  by a pair of tools  29 ,  30  on the die breast  11  and slide  12 , respectively. Next, the bolt  26  is transferred to the third station  15  where a flange is formed between die and punch tools  31 ,  32 . Thereafter, the bolt  26  is transferred to the fourth or last forming station  16  where the flanged head is supported in a sleeve  33  on the slide  12  and the distal end of the shank is pointed in an extrusion die  42 . A spring assembly  43  is disposed in the sleeve  33  and is effective in temporarily supporting the bolt  26  to facilitate transferring action.  FIG. 8  illustrates the forth station  16  in a vertical cross-section on a somewhat enlarged scale over  FIG. 1 . 
         [0023]      FIG. 7  illustrates the sleeve  33  in exploded relation to a case  44  in which it is selectively axially positioned in accordance with the length of bolt  26  being produced. A forward face or surface  46  of the sleeve  33  supports the head of the bolt  26  during the pointing or forming step at the fourth station  16  depicted in  FIG. 1 . Both the sleeve  33  and case  44  are generally cylindrical tubular bodies. An outside diameter or surface  47  of the sleeve  33  is proportioned with a close fit to a bore  48  of the case  44 . The exterior  47  of the sleeve  33  is cut with pairs of opposed chordal slots  51 . The case  44  is similarly cut with pairs of opposed chordal slots  52  that extend through the wall of the case. 
         [0024]    The axial position of the sleeve  33  in the case  44  is fixed by a pair of identical keys  53  having chordal profiles. Outer circular or peripheral areas  56  of the keys  53  have a radius that is essentially the same as the radius of the outer surface of the cylindrical case  44 . The axial dimension of the major thickness of the keys  53  provides a close fit with the axial length or width of the case slots  52 . At their central area, the keys  53  have chordal webs  57  of an axial thickness half that of the outer or major parts of the keys and are sized to closely fit into the slots or notches  51  in the sleeve  33 . Preferably, the axial dimensions of the key webs  57 , key periphery  56 , sleeve slots  51 , sleeve slot axial spacings, case slots  52 , and case slot spacings are all units or multiples of the increments that the standard bolts differ in length, e.g. 2, 4, or 5 mm. When tooling is set up to make a particular bolt length, the sleeve  33  is positioned in the case  44  at a desired location, the keys  53  are placed in whichever sleeve and case slots  51 ,  52  line up (on each side of the case) and this sleeve, case, and key assembly is slipped into the sleeve of the respective work station  16  ( FIGS. 1 and 5 ) or  15  ( FIGS. 3 and 4 ). By properly setting the sleeve  33  in the case  44 , standard length threaded to the head bolts can be produced using the same pointing die  42 . 
         [0025]    A bolt with a head having a hex shape or otherwise non-circular form should not rotate when being transferred from one station to another, so that the head will be angularly registered with the tools at the succeeding station. The risk of unwanted rotation, in accordance with the invention, is reduced by locking the part against such rotation, while it is being picked up by the transfer fingers, with a formation of a small diametral chisel edge or projection  60  on the end face of knockout pins  61  in the relevant work stations. At various stations, a knockout pin  61  lies at the center line of a work station. Typically, the knockout pin extends through a bore  65  in hard plate  62  mounted on the die breast  11  and backing up or axially supporting the tooling against forming loads at the respective die station. With reference to  FIG. 10 , the angular orientation or position of the hard plate  62  in a cylindrical bore  63  of a circular case  64  is maintained, in accordance with the invention, by headless set screws  66  received in axially oriented, threaded, semi-circular slots  67  in quadrature on its periphery and open to the bore  63 . The hard plate  62  has a complementary set of axially extending semi-circular slots  68  arranged, in quadrature, on its periphery to register with and complement the slots  67  in the bore  63 . The associated knockout pin  61  and, therefore, its chisel end face is maintained in a proper orientation with reference to the hard plate  62  by a shoe  69  biased by bevel springs  71  against an elongated flat  72  on a side of the knockout pin. The springs  71  and shoe  69  are retained in a radial bore  73  in the hard plate  62  by an axially oriented pin  74 . The shoe  69 , bearing against the flat  72 , allows the pin  61  to reciprocate but prevents rotation of the pin about its longitudinal axis. 
         [0026]      FIG. 2  illustrates the inventive process and tooling as applied to producing standard hex flange bolts, again under the European standard DIN EN 1662 where the standard lengths are greater than the standard threaded to the head lengths as discussed with respect to  FIG. 1  above. Machine elements or parts that are the same or similar to that described in connection with  FIG. 1  are identified with the same numerals here in  FIG. 2  and, below, with reference to  FIGS. 3 through 5 , and certain other figures. The sequence of transferring bolts discussed in reference to  FIG. 1 , similarly, is the same for the tooling set ups in  FIGS. 2 through 5 . The bolt  76  begins successive heading, pointing, and roll diameter formation at the first work station  13  where it is upset to partially form the head with punch and die tools  77 , and  78 . At the second forming station  14 , a hex shape is extruded on the head by cooperating tools  79 ,  80  on the slide  12  and die breast  11 , respectively. In the third work station  15 , opposed tools  83  and  84  form the flange of the head in an upset action, and a tool or die insert  39  in a limited extrusion like action forms a point on the distal end of the bolt shank. 
         [0027]    At the fourth station  16  also depicted in a vertical cross-section in  FIG. 9 , the distal end of the bolt shank is extruded in a die insert or tool  86  reducing its diameter to that of a roll diameter along a length corresponding to a standard thread length. The head of the bolt  76  at this station  16  is axially supported and driven by the sleeve  33  described above in connection with  FIG. 7 . In the set-up of  FIG. 2 , the sleeve  33  is held by the keys  53  towards the rear of the case  44  such that the head and a significant portion of the shank is received in the case. The stepwise multiple positions of the sleeve, similar to its use in the process described in connection with  FIG. 1 , allows a single die insert  86  to be used to extrude the roll diameter on a plurality of lengths and preferably the full range of standard lengths of partially threaded bolts. 
         [0028]    Returning to the discussion of the process at the third station  15 , differences in the lengths of bolts in a standard range are, in accordance with the invention, accounted for by axially shifting a pointing tool or insert in its respective case and/or substituting another insert with an incrementally different axial location of the pointing area or throat in the insert, the differences in location corresponding to differences in standard bolt lengths.  FIGS. 6   a - i , illustrate these variations, the numerals  37 ,  38 ,  39  and  40  identifying different inserts. The elements  34  are fillers of equal length. 
         [0029]      FIG. 3  illustrates the inventive process and tooling applied to making threaded to the head hex head screws or bolts such as conforming to European Standard DIN EN ISO 4017. Like the process shown in  FIG. 1 , wire stock fed to the cut off station  19  is slightly less than the nominal roll diameter of the finished blank. At the first station  13 , a bolt  91 , with this near a roll diameter along substantially the full length of its shank, has its head initially coned or upset in punch and die tools  92 ,  93 , respectively. At the second station  14 , the head is further upset between punch and die tools  94 ,  95 . The bolt  91  is pointed in an extrusion like process in a die  96  on the die breast  11  at the third station  15 . Differences in the lengths of hex head bolts are accounted for by the multiple position sleeve  33 , optionally having its face modified to conform to the intermediate head profile of the bolt  91  at this station  15  with the case  44  and keys  53  as disclosed in connection with the set up of  FIG. 1 . Additionally, the die or insert  96  can be double ended and reversed end for end to change the axial location of the operative extrusion like pointing throat and thereby supplement the range of position adjustment offered by the sleeve  33  carried on the slide  12 . The cross section of the head of the bolt  91  preferably produced in the first two stations  13 ,  14 , is generally circular. In the fourth station  16 , the head of the bolt  91  is trimmed into a hex between opposed tools  97 ,  98 . 
         [0030]    Referring to  FIG. 4 , conventional partially threaded hex head pointed bolts are made with the inventive process and tooling. Such bolts can conform to the DIN EN ISO 4014 standard. The head of a bolt  101  is initially headed or coned at the first station  13  between tools  102 ,  103 . At the second station  14 , the head is further upset by tools  104 ,  105  and the distal end of the shank is pointed by an extrusion like tool  39 . The specific length of the bolt  101  is accounted for by using the dies, fillers, and techniques described in connection with  FIGS. 2 and 6  with reference to the set up at the third station of  FIG. 2 . The roll diameter of the bolt  101  is extruded on the shank at the third station  15  in a tool or insert  86  which can be the same tool as used in the set up of  FIG. 2  at the fourth station  16 . Variations in the length of the bolt  101  can be accommodated by the multi-position sleeve  33  as explained above. The head of the bolt  101  is trimmed to a hex shape at the fourth station by tools  106 ,  107 . 
         [0031]      FIG. 5  illustrates the method and tooling by which the invention produces threaded to the head socket head cap screws  111  such as specified in the DIN EN ISO 4762 standard. Again, like the processes shown in  FIGS. 1 and 3 , wire stock fed to the cut off station  19  is slightly less than the nominal roll diameter of the finished blank to account for incidental growth in diameter at the work stations  12 - 16 . The bolt  111  with the near roll diameter along its shank has its head initially upset in the first station  13  in die and punch tools  112 ,  113 . At the second station  14 , the bolt  111  is progressively formed by further upsetting the head in tools  114 ,  115 . At the third station  15 , the bolt head is fully upset and formed with an internal hexagonal blind hole with punch and die tools  116 ,  117 . At the last station  16 , the part is forced into a die tool the same as or like the tool  42  used on the last die station illustrated in  FIG. 1 . As in  FIG. 1 , the sleeve  33  or an equivalent thereof can be appropriately positioned in the case  44  on the slide in the last station  16  to account for differences in the lengths of the bolts  111  being produced. 
         [0032]    While the invention has been shown and described with respect to particular embodiments thereof, this is for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein shown and described will be apparent to those skilled in the art all within the intended spirit and scope of the invention. Accordingly, the patent is not to be limited in scope and effect to the specific embodiments herein shown and described nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.

Technology Category: b