Apparatus for forming self locking fasteners

Abstract

For the production of screw fasteners with plastic patches thereon, the fasteners are preheated to a high temperature. Each heated fastener pauses at a processing station where a predetermined increment of a plastic strip is severed and dropped onto the hot fastener and as the plastic melts a pressure shoe forms the plastic to the curved cross-sectional configuration of the fastener. The fasteners are then quenched. For high production a number of the fasteners are processed simultaneously on each of the repeated cycles of operation. The apparatus is readily adjustable to handle fasteners of different sizes.

I claim: 
     
       1. .[. In an apparatus for forming a plastic patch on a workpiece having a curved cross-section configuration, for example, on the screw thread of a fastener, the combination of: means to place a workpiece in preselected position at a processing station;   means to advance an increment of plastic strip to a position above the workpiece;   means to shear off a fragment from the increment and to carry the fragment to the workpiece, and   means having a curved working face shaped to a curvature that is substantially complementary to the curvature of the workpiece to press the sheared fragment of plastic strip against the curved surface of the workpiece for adherence thereto..]. .Iadd.An apparatus for forming a plastic patch on a workpiece which is an externally threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising:   means for heating the threaded fastener to an elevated temperature sufficient to convert the plastic patch to a completely molten state when the patch is brought into contact with the heated fastener;   means to place the heated fastener in a preselected position at a processing station;   means to advance an increment of plastic strip to a position adjacent the heated fastener;   means for cutting a fragment from the increment and to carry the fragment to the heated fastener;   means having a smooth working face which is shaped to a curvature that is substantially complementary to the curvature of the threaded fastener to press the fragment of plastic strip about the fastener and into engagement with the crests of the threads of the heated fastener, and   means to yieldingly move said means having a smooth working face against said heated fastener with a force which applied a work shaping pressure to the fragment that is sufficient to hold the fragment engaged with the crests of the threads of the heated fastener without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient for the heated crests of the fastener to sever the fragment into discrete segments which in a completely molten state flow downwardly of the crests and into the valleys between adjacent crests of the threads to adhere to adjacent flanks of the threads in forming a unitary plastic patch on the threads in which accurately predetermined quantities of the plastic are present in each of the discrete severed segments of the plastic patch. .Iaddend.   
     
     
       2. .[. A combination as set forth in claim 1 which includes means providing a heating zone to heat the workpieces; and which includes means to convey the workpieces through the heating zone to deliver the workpieces to the processing station..]. .Iadd.The apparatus of claim 1 which includes means providing a heating zone to heat the fasteners,   means to convey the fasteners through the heating zone to deliver the heated fasteners to the processing station. .Iaddend.   
     
     
       3. .[. A combination as set forth in claim 1 which includes driving means to actuate the moving parts of the apparatus through successive operating cycles; and which includes guide means for gravitational movement of the workpieces through said processing station and beyond..]. .Iadd.An apparatus for forming a plastic patch on a workpiece which is an externally threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising: means for heating the threaded fastener to an elevated temperature sufficient to convert the plastic patch to a completely molten state when the patch is brought into contact with the heated fastener;   means to place the heated fastener in a preselected position at a processing station;   means to advance an increment of plastic strip to a position adjacent the heated fastener;   means for cutting a fragment from the increment and to carry the fragment to the heated fastener;   means having a smooth working face which is shaped to a curvature that is substantially complementary to the curvature of the threaded fastener to press the fragment of plastic strip about the fastener and into engagement with the crests of the threads of the heated fastener;   means to yieldingly move said means having a smooth working face against said heated fastener with a force which applies a work shaping pressure to the fragment that is sufficient to hold the fragment engaged with the crests of the threads of the heated fastener without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient for the heated crests of the fastener to sever the fragment into discrete segments which in a completely molten state flow downwardly of the crests and into the valleys between adjacent crests of the threads to adhere to adjacent flanks of the threads in forming a unitary plastic patch on the threads in which accurately predetermined quantities of the plastic are present in each of the discrete severed fragments of the plastic patch;   guide means for providing gravitational movement of the workpieces through said processing station and beyond, and   driving means to actuate the moving parts of said apparatus through successive operating cycles. .Iaddend.   
     
     
       4.  A combination as set forth in claim 3 in which said guide means comprises a chute which has an inclined portion extending downward from a receiving station past the processing station, said chute having a terminal portion which is not downwardly inclined; and which includes means operating in said cycle to discharge the workpieces from the terminal portion of the chute. .[.5. A combination as set forth in claim 3 which includes a stop at the processing station to interrupt the gravitational movement of a workpiece and to hold the workpiece in position for processing; and which includes, means operating in said cycle to move the stop between a retracted position and its effective position to interrupt the gravitational movement of a workpiece..]. .Iadd.An apparatus for forming a plastic patch on a workpiece which is a threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising: means for heating at least a portion of the workpiece to a temperature in excess of the flow point of the plastic;   means to place the workpiece in a preselected position at a processing station including guide means for gravitational movement of a workpiece through said processing station and beyond with a stop at the processing station to interrupt the gravitational movement of a workpiece and to hold the workpiece in position for processing with means operating in the cycle of said apparatus to move the stop between a retracted position and its effective position to interrupt the gravitational movement of a workpiece;   means to advance an increment of plastic strip to a position adjacent the workpiece;   means for cutting a fragment from the increment to carry the fragment to the workpiece;   means having a curved working face shaped to a curvature that is substantially complementary to the curvature of the workpiece to press the fragment of plastic strip about the curved surface of the workpiece with work shaping pressure sufficient only to hold the fragment engaged with the crests of the threads of the workpiece and without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient to cause the material of the fragment to melt and in a molten state to flow into each valley of the adjacent threads engaged with said fragment, and   driving means to actuate the moving parts of said apparatus through   
     
     
        successive operating cycles. .Iaddend. 6. A combination as set forth in claim 5 in which the position of the stop at the processing station is adjustable for cooperation of the stop with workpieces of different sizes. 
     
     
        . A combination as set forth in claim 6 which includes means operating in said cycle to advance the stop means from its retracted position to its effective position, said advancing means being spring-loaded to permit the stop means to be stopped at selected positions for cooperation with workpieces of different sizes;   and which includes adjustable means to block the advance of the stop means   
     
     
        at the selected positions. 8. .[. A combination as set forth in claim 3 which includes means at a receiving station synchronized with the cycle of operation to release a workpiece to the guide means for movement to the processing station on each cycle; which includes means to sense the presence or absence of a workpiece at the receiving station;   and which includes means responsive to the sensing means to disable the strip-advancing means temporarily in the absence of a workpiece at the receiving station..]. .Iadd.An apparatus for forming a plastic patch on a workpiece which is a threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising:   means for heating at least a portion of the workpiece to a temperature in excess of the flow point of the plastic;   means to place the workpiece in a preselected position at a processing station which includes guide means for gravitational movement of a workpiece through said processing station and beyond with means at said receiving station synchronized with the cycle of operation of said apparatus to release a workpiece to the guide means for movement of the workpiece to the processing station on each cycle with means to sense the presence or absence of a workpiece at said receiving station;   means to advance an increment of plastic strip to a position adjacent the workpiece;   means responsive to said sensing means to temporarily disable said means to advance an increment of plastic strip in the absence of a workpiece at said receiving station;   means for cutting a fragment from the increment and to carry the fragment to the workpiece;   means having a curved working face shaped to a curvature that is substantially complementary to the curvature of the workpiece to press the fragment of plastic strip about the curved surface of the workpiece with work shaping pressure sufficient only to hold the fragment engaged with the crests of the threads of the workpiece and without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient to cause the material of the fragment to melt and in a molten state to flow into each valley of the adjacent threads engaged with said fragment, and   driving means to actuate the moving parts of said apparatus through   
     
     
        successive operating cycles. .Iaddend. 9. A combination as set forth in claim 8 which includes electrically actuated means to prevent operation of the means to advance an increment of the plastic strip; and in which said sensing means includes a switch to energize said   
     
     
        electrically actuated means. 10. .[. A combination as set forth in claim 1, including: a patch-applying assembly that is movable from an upper retracted position to a lower position into contact with the workpiece;   said patch-applying assembly including said means to advance an increment of plastic strip, said means to shear a fragment from the increment of the plastic strip after a strip has been advanced, and said means to press the sheared fragment of plastic against the workpiece after the plastic strip has been sheared off;   a first clamp means positioned at said station, and   a second clamp means carried by said patch-applying assembly, with said first and second claim means cooperating to clamp the workpiece when the patch-applying assembly is moved to a lower position and the sheared fragment of plastic strip is pressed against the workpiece..]. .Iadd.An apparatus for forming a plastic patch on a workpiece which is an externally threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising:   means for heating the threaded fastener to an elevated temperature sufficient to convert the plastic patch to a completely molten state when the patch is brought into contact with the heated fastener;   means to place the heated fastener in a preselected position at a processing station;   means to advance an increment of plastic strip to a position adjacent the heated fastener;   means for cutting a fragment from the increment and to carry the fragment to the heated fastener;   means having a smooth working face which is shaped to a curvature that is substantially complementary to the curvature of the threaded fastener to press the fragment of plastic strip about the fastener into engagement with the crests of the threads of the heated fastener;   means to yieldingly move said means having a smooth working face against said heated fastener with a force which applies a work shaping pressure to the fragment that is sufficient to hold the fragment engaged with the crests of the threads of the heated fastener without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient for the heated crests of the fastener to sever the fragment into discrete segments which in a completely molten state flow downwardly of the crests and into the valleys between adjacent crests of the threads to adhere to adjacent flanks of the threads in forming a unitary plastic patch on the threads in which accurately predetermined quantities of the plastic are present in each of the discrete severed segments of the plastic patch;   a patch-applying assembly including said means for cutting a fragment from an increment of plastic strip after the strip has been advanced and said means to press the fragment of plastic about the fastener after the fragment has been cut from the increment of plastic strip;   said patch-applying assembly being movable from an upper retracted position to a lower position into contact with the fastener;   a first clamp means positioned at said processing station, and   a second clamp means carried by said patch-applying assembly, with said first and second clamp means cooperating to clamp the fastener when the patch-applying assembly is moved to a lowered position and the fragment of   
     
     
        plastic strip is pressed about the fastener. .Iaddend. 11. A combination as set forth in claim 10 in which said means to .[.shear.]. .Iadd.cut .Iaddend.the increment comprises a pair of cutting edges, one of the 
     
     
        cutting edges being on said second clamp means. 12. A combination as set forth in claim 10 in which said assembly comprises: a reciprocative plunger;   a head slidingly mounted on the plunger and movable relative thereto between a position extending beyond the plunger and a retracted position,   said plunger being said pressing means;   spring means acting between the plunger and the head to urge the head to its relative extended position,   said second clamp means being on the leading end of the head to contact the workpiece before the plunger makes contact with the workpiece when the assembly advances,   said plunger and head respectively having cutting edges cooperative to .[.shear.]. .Iadd.cut .Iaddend.said strip in response to retraction of the head relative to the plunger by impingement of the head against the   
     
     
        workpiece. 13. A combination as set forth in claim 12 which includes actuating means to reciprocate the plunger, said actuating means including spring means to yield when the plunger contacts the workpiece and to cause the plunger to exert pressure against the workpiece after the plunger 
     
     
        contacts the workpiece. 14. A combination as set forth in claim 13 which includes mechanism carried by the head to advance the increment of the plastic strip, said mechanism being actuated by advance of the head 
     
     
        towards the workpiece. 15. A combination as set forth in claim 14 which includes a rack and a cooperating pinion to actuate said mechanism, the rack being stationary adjacent the path of reciprocation of the head, the pinion being carried by the head for rotation by the rack means and being 
     
     
        connected to the mechanism for actuation thereof. 16. A combination as set forth in claim 15 in which the rack is adjustable longitudinally of the path of advance of the head to adjust the length of said increment of the 
     
     
        plastic strip. 17. The combination as set forth in claim 15 which includes means to retract the rack out of the path of the pinion to prevent operation of the mechanism in the absence of a workpiece at said station. 
     
     
         8. A combination as set forth in claim 17 which includes solenoid means 
     
     
        to retract the rack in the absence of a workpiece at said station. 19. A combination as set forth in claim 17 which includes means responsive to the absence of a workpiece at said station; and in which said retracting 
     
     
        means is responsive to the responsive means. 20. In an apparatus for forming a plastic patch on a workpiece, for example on the screw thread of a fastener, the combination of: .Iadd. means for heating the workpiece to a temperature in excess of the flow point of the plastic; .Iaddend.   means to support successive workpieces in reclining position at a processing station;   a plunger above the processing station;   means to reciprocate the plunger between an upper retracted position and a lower advanced position in contact with a workpiece at said processing station;   a head mounted on the leading end of the plunger to contact a workpiece at the processing station and movable relative to the plunger between a retracted position and a position extending beyond the leading end of the plunger;   yielding means effective between the head and the plunger to urge the head to its advanced position relative to the plunger;   means carried by the head to advance an increment of plastic strip in response to reciprocation of the head with the plunger;   cutting edges on the plunger and head respectively cooperative to cut off the advanced increment of the plastic strip in response to retraction of the head relative to the plunger by impingement of the head against a workpiece,   whereby the advance of the plunger causes in sequence:   advance of an increment of the plastic strip;   abutment of the head against a workpiece;   advance of the plunger towards the workpiece after the head contacts the workpiece with consequent pressing of the head against the workpiece by yielding means;   continued advance of the plunger to cooperate with the head to sever the advanced increment of the plastic strip; and   continued advance of the plunger to press the severed plastic strip against the workpiece .Iadd.with work shaping pressure sufficient only to hold the severed plastic strip engaged with the crests of the threads of the workpiece and without pressurally forcing the material of the fragment into the valleys of the threads for time sufficient to cause the material of the fragment to melt and in a molten state to flow into each valley of   
     
     
        the adjacent threads engaged with said fragment. .Iaddend. 21. A combination as set forth in claim 20 in which the workpiece is curved in cross-sectional configuration and in which the leading end of the plunger is curved in accord with the cross-sectional concurvature of the 
     
     
        workpiece. 22. A combination as set forth in claim 20 in which the means to reciprocate the plunger includes a yielding operating connection to the plunger to permit the plunger to be stopped by contact with the workpiece and to cause the plunger to exert pressure against the workpiece after the 
     
     
        workpiece stops the plunger. 23. A combination as set forth in claim 20 in which the workpieces are heated and in which said head is water cooled to 
     
     
        prevent excessive heating of the head by the heated workpieces. 24. A combination as set forth in claim 20 in which said means to advance an increment of the plastic strip comprises a rack and a pinion for rotation by the rack, the rack being positioned adjacent the path of movement of the head and the pinion being carried by the head, the pinion being operatively connected to the means for advancing an increment of the 
     
     
        plastic strip. 25. .[. A combination as set forth in claim 24 which includes means operative to retract the rack out of the path of the pinion to prevent advance of an increment of the plastic strip in the absence of a workpiece at the processing station..]. .Iadd.In an apparatus for forming a plastic patch on a workpiece, for example on the screw thread of a fastener, the combination of: means for heating the workpiece to a temperature in excess of the flow point of the plastic;   means to support successive workpieces in reclining position at a processing station;   a plunger above the processing station;   means to reciprocate the plunger between an upper retracted position and a lower advanced position in contact with a workpiece at said processing station;   a head mounted on the leading end of the plunger to contact a workpiece at the processing station and movable relative to the plunger between a retracted position and a position extending beyond the leading end of the plunger;   yielding means effective between the head and the plunger to urge the head to its extended position relative to the plunger;   means carried by the head to advance an increment of plastic strip in response to reciprocation of the head with the plunger which includes a rack and a pinion rotated by the rack with the rack being positioned adjacent the path of movement of the head and the pinion carried by the head and the pinion operatively connected to the means for advancing an increment of the plastic strip;   means operative to retract the rack out of the path of the pinion to prevent advance of an increment of the plastic strip in the absence of a workpiece at the processing station;   cutting edges on the plunger and the head respectively cooperative to cut off the advanced increment of the plastic strip in response to retraction of the head relative to the plunger by impingement of the head against a workpiece,   whereby the advance of the plunger causes in sequence:   advance of an increment of the plastic strip;   abutment of the head against a workpiece;   advance of the plunger towards the workpiece after the head contacts the workpiece with consequent pressing of the head against the workpiece by said yielding means;   continued advance of the plunger to cooperate with the head to sever the advanced increment of the plastic strip, and   continued advance of the plunger to press the severed plastic strip against the workpiece with work shaping pressure sufficient only to hold the severed plastic strip engaged with the crests of the threads of the workpiece and without pressurally forcing the material of the fragment into the valleys of the threads for a time sufficient to cause the material of the fragment to melt and in a molten state to flow into each   
     
     
        valley of the adjacent threads engaged with said fragment. 26. A combination as set forth in claim 25 in which the rack is adjustable along the path of movement of the head to adjust the extent to which the pinion is actuated by the rack thereby to adjust the length of said increment of 
     
     
        the plastic strip. .[.27.  An apparatus for forming a threaded fastener having self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising: means for heating a threaded fastener to a temperature in excess of the flow point of the plastic;   means for transferring the heated fastener to a work station on said apparatus;   means for feeding a flat ribbon of a preselected thickness of the plastic to said work station;   means at said work station for cutting a fragment of a predetermined length from said ribbon with said fragment having a width substantially less than the circumference of the major diameter of the threads of the fastener;   means at said work station for placing and holding the fragment of the flat ribbon of the plastic on the heated fastener at a preselected location thereon and for pressurally shaping the said fragment to the circumference of the major diameter of the threads with sufficient work shaping pressure to hold said fragment about the circumference of the major diameter of the threads and against longitudinal and radial movement relative to the said threads for a time sufficient to cause the heated crests of the threads engaged with said fragment to sever the fragment into discrete segments whereby accurately predetermined quantities of the plastic formed by the discrete segments melt and flow downwardly of the crests and into the valleys between adjacent crests of the threads to adhere to adjacent flanks of the threads to form a unitary coadhesive patch of the plastic at the said preselected location thereon; and    means for transferring said fastener with the plastic adhered to the   
     
     
        threads of the same from said work station..]. .[.28.  An apparatus for forming a threaded fastener having self-locking characteristics by reason of a patch of polyester adhered to a preselected plurality of unmodified threads of the fastener comprising: means at one work station on said apparatus for heating a threaded fastener to a temperature in excess of the flow point temperature of the polyester;   means for transferring said heated fastener to a second work station on said apparatus;   means for advancing a flat ribbon of a preselected thickness of the plastic polyester to said second work station;   means at said second work station for cutting a fragment of a predetermined length from said ribbon with the fragment having a width substantially less than the circumference of the major diameter of the threads of the fastener, including means for pressurally engaging said fragment with the heated fastener at a preselected location thereon and for simultaneously pressurally shaping the said fragment to the circumference of the major diameter of the threads with sufficient work shaping pressure to hold said fragment against longitudinal and radial movement relative to said threads for a time sufficient to cause an amount of the polyester determined by the longitudinal extent of the fragment between adjacent crests of the threads to melt and flow into each valley of adjacent threads engaged with said fragment and outwardly of the same to form a unitary coadhesive patch of the polyester adhered to the threads of the fastener at the preselected location thereon;   means for transferring said fastener from said second work station to a third work station; and   means at said third work station for abruptly cooling the fastener to solidify the polyester adhered to the threads thereof..]..Iadd. 29. The apparatus of claim 1, including:   a patch-applying assembly that is movable from an upper retracted position to a lower position into contact with the workpiece, and   said patch-applying assembly including said means to cut a fragment from the increment of plastic strip after the strip has been advanced, and said means to press the fragment of plastic material about the workpiece after the fragment has been cut from the plastic strip. .Iaddend..Iadd. 30. The apparatus of claim 29 wherein   said patch-applying assembly includes said means to advance an increment of plastic strip, and   said means to advance an increment of plastic strip is actuated by movement of said patch-applying assembly. .Iaddend. .Iadd. 31. The apparatus of claim 1 in which said means to cut said fragment includes   a pair of cutting edges for cutting said fragment;   one of said cutting edges being on said means having a curved working face, and   said means having a curved working face then carrying said fragment to said workpiece, and thereafter pressing said fragment about the curved heated surface of said workpiece. .Iaddend..Iadd. 32. An apparatus for forming a plastic patch on a workpiece which is an externally threaded fastener to provide the fastener with self-locking characteristics by reason of a patch of plastic adhered to a plurality of unmodified threads of the fastener comprising:   means for heating the threaded fastener to an elevated temperature sufficient to convert the plastic patch to a completely molten state when the patch is brought into contact with the heated fastener;   means to place the heated fastener in a preselected position at a processing station;   means to advance an increment of plastic strip to a position adjacent the heated fastener;   means for cutting a fragment from the increment and to carry the fragment to the heated fastener;   means having a smooth working face which is shaped to a curvature that is substantially complementary to the curvature of the threaded fastener to press the fragment of plastic strip about the fastener and into engagement with the crests of the threads of the heated fastener;   means to yieldingly move said means having a smooth working face against said heated fastener with a force which applies a work shaping pressure to the fragment that is sufficient to hold the fragment engaged with the crests of the threads of the heated fastener without pressurally forcing material of the fragment into the valleys of the threads for a time sufficient for the heated crests of the fastener to sever the fragment into discrete segments which in a completely molten state flow downwardly of the crests and into the valleys between adjacent crests of the threads to adhere to adjacent flanks of the threads in forming a unitary plastic patch on the threads in which accurately predetermined quantities of the plastic are present in each of the discrete severed segments of the plastic patch;   a patch-applying assembly that is movable from an upper retracted position to a lower position into contact with the fastener;   said patch-applying assembly including said means to cut a fragment from the increment of plastic strip after the strip has been advanced and said means to press the fragment of plastic material about the workpiece after the fragment has been cut from the plastic strip;   said means to press the fragment of plastic material about the workpiece including a reciprocative plunger in said assembly;   actuating means to move said assembly and said plunger toward said fastener;   stop means to interrupt the movement of said assembly when it approaches said fastener, and   said plunger then continuing its movement to press said fragment about said fastener. .Iaddend..Iadd. 33. The apparatus of claim 32 wherein   said patch-applying assembly includes said means to advance an increment of plastic strip, and   said means to advance an increment of plastic strip is actuated by movement of said patch-applying assembly. .Iaddend. .Iadd. 34. The apparatus of claim 1 including:   a single drive means, and   means interconnecting said drive means with the moving parts of said apparatus to actuate the moving parts of the apparatus through successive operating cycles. .Iaddend..Iadd. 35. The apparatus of claim 20 including:   a single drive means, and   means interconnecting said drive means with the moving parts of said apparatus to actuate the moving parts of the apparatus through successive operating cycles. .Iaddend.