Method Of Clamping And Riveting Parts

Abstract

Wire slugs for use as rivets are passed from a slug-forming station to a partial riveting station where a ram forces a slug through a restricted orifice in a spring-loaded guide and clamp member so that the guide and clamp member is pressed against the parts to be riveted as the slug is forced through the orifice into aligned holes in the parts. The parts are positioned upon an anvil which may be a fixture mounted on a turntable moveable from station to station, and the anvil has recesses into which the lower portion of the slug is forced to form a lower cap. The hole in the bottom part is preferably slightly smaller than the hole through the top part so that the slug material will flow outwardly filling the top hole. locking the parts in place and rendering hole alignment noncritical. Upon retraction of the ram, the spring-loaded guide and clamp member is elevated above the partially formed rivet and the two joined parts. The subassembly and anvil may then be moved to a rivet completion station where formation of a top rivet cap may be completed.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a riveting method and apparatus, and more particularly to an automatic riveting technique which may be employed in an assembly line operation to rivet parts to one another.

Although the riveting art is old and well developed, there are still a number of problems associated with this technique, particularly in automatic riveting systems. For example, a frequently occurring problem is that the rivet in the final product does not completely fill the holes in the parts through which it extends and thus the rivet is loose allowing for slight movement of the parts and reducing the strength of the united parts. In the case of automatic riveting systems, there are problems concerned with properly feeding the slugs from which the rivets are formed and with maintaining alignment of the parts to be riveted during the rivet-forming step. A common cause of work stoppage is loose rivets jammed into guide and feed systems.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide an improved automatic riveting system.

Another object of the invention is to provide novel riveting apparatus which eliminates loose rivets and provides a stronger joint between the riveted parts.

Still another object of the invention is to provide a riveting apparatus in which pressure generated by extruding a slug through an orifice in the course of positioning the rivet-forming slug in aligned holes within the parts to be riveted is also utilized to clamp the parts in position.

A further object of the invention is to provide an improved, novel automatic riveting process in an assembly line operation.

Briefly, the present invention utilizes apparatus for feeding a metal or appropriate synthetic plastic rod to a reciprocating shear punch which shears off a slug from the rod and positions the slug over a spring loaded transfer guide and clamp member. A ram then pushes the slug out of the shear punch and extrudes the slug through a restricted sizing orifice in the guide and clamp member into aligned holes on superimposed parts to be riveted which are positioned upon an anvil. The extrusion pressure forces the transfer guide and clamp member downwardly against a biasing force so that the parts to be riveted are clamped in position between the guide and clamp member and the anvil. At this time, a cap is partially formed on the lower end of the rivet. The hole in the upper part to be riveted is preferably slightly larger than the hole in the lower part so that the upper periphery of the rivet can expand into the larger hole locking the parts to each other even though there is not an upper cap on the rivet at this time. Using a larger hole in the upper part than the lower part eliminates the requirement of positioning the parts to close tolerances.

Upon retraction of the ram, the spring-loaded transfer guide and clamp member is elevated out of contact with the united parts. To facilitate this, the lower portion of the opening through the guide and clamp member flares outwardly and downwardly to prevent binding of the expanded rivet to the sides of the member opening. This should be configured to a nonlocking angle like a lathe collet. The anvil, which may be in the form of a fixture on an indexed turntable, may now be moved to a rivet completion station, if desired, where a second ram descends onto the partially formed rivet to complete the formation of the rivet insuring that the holes in the parts are completely filled and that caps are formed on each end of the rivet. After retraction of the second ram, the anvil is moved to a further station at which the finished article is discharged and the anvil is returned to a parts feeding station for the commencement of another cycle of operation.

The above and other objects, features and advantages of the invention will become more apparent as this description proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat diagrammatic view, partially in section, of a presently preferred embodiment of the invention;

FIG. 2 is a view of a portion of the apparatus of FIG. 1 showing the spring-loaded transfer guide and clamp member in its lower, part-clamping position;

FIG. 3 is a view taken primarily in vertical section showing a partially-formed rivet at the rivet completion station; and

FIG. 4 is a view similar to FIG. 3 but showing the arrangement of the apparatus at the completion of the rivet-forming operation.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawing and more particularly to FIG. 1, a metal rod 10, which is the stock material for the production of the rivets, is progressively fed downwardly through a stationary, hollow cylindrical rod guide 12 by a chuck feed mechanism or the like (not shown) into an opening 14 in a reciprocating shear punch 16 when the punch is in a retracted position in which the opening 14 is beneath the opening in the rod guide 12. Movement of punch 16 towards the position shown in FIG. 1 causes a slug 18 to be sheared off of the rod 10. At the conclusion of the outward stroke or movement of punch 16, the slug 18 is positioned as shown in FIG. 1 directly beneath a ram 20 which has an outer diameter slightly smaller than the inner diameter of the opening 14 in the punch 16. Punch 16 reciprocates on top of a support 22. A slug transfer guide and clamp member 24 is disposed beneath punch 16 in alignment with ram 20 and is connected to support 22 so as to enable vertical movement of the guide and clamp member relative to support 22. A spring 26 normally maintains the guide and clamp member biased into the position shown in FIG. 1 in which this member abuts the lower surface of support 22.

As shown in FIGS. 1 and 2, the guide and clamp member 24 has a passageway through which the slug 18 is forced. The passageway has an outwardly flaring inlet or mouth 28 which has a diameter greater than that of the slug and which includes a restricted sizing orifice 30 which has a diameter slightly smaller than that of slug 18, and an outwardly flaring discharge section 32.

A pair of upper and lower parts 34 and 36 to be riveted to each other are positioned upon an anvil 38 when the anvil is at a part feed station (not shown), and then the anvil is moved to the position shown in FIGS. 1 and 2. By way of example, the anvil 38 may be part of an indexed turntable having a plurality of anvils disposed about its periphery. The upper and lower parts 34 and 36 have aligned holes 40 and 42 respectively which, as seen in FIGS. 1 and 2, are not only aligned with each other but with the passageway through the transfer guide and clamp member 24. The diameter of hole 40 in the upper part is preferable greater than the diameter of the hole 42 in the lower part. As has been stated, this differential sizing allows parts placement without adhering to close tolerances.

Upon the downstroke of ram 20, the slug 18 is pushed downwardly out of the hole 14 in punch 16 and through the restricted sizing orifice 30. Since orifice 30 is smaller than the initial diameter of slug 18, it is necessary to extrude the slug through orifice 30. The resulting generated pressure acting upon the wall of the passageway through guide and clamp member 24 just above orifice 30 forces the guide and clamp member downwardly against the bias of spring 26 into the position shown in FIG. 2. In this position, the lower surface 44 of the guide and clamp member 24 is pressed against the upper surface of part 34 thereby clamping parts 34 and 36 between it and the upper surface of anvil 38. With the parts 34 and 36 now firmly held in position by the pressure generated in extruding the slug through orifice 30, further downward movement of ram 20 causes the lower end of the slug 18 to assume the configuration illustrated in FIG. 2 in which the lower end of the slug has partially filled recess 46 in the anvil 38. This recess has the configuration of the cap desired at the bottom of the rivet. At the same time, the sides of slug 18 expand outwardly filling the hole 42 in the lower part 36 and at least substantially filling the larger hole 40 in the upper part 34. The expanded portion of the slug in hole 40 overlies the upper, inwardly extending peripheral edge of the lower part 36 in the vicinity of hole 32 so that parts 34 and 36 are rigidly connected to each other even though the rivet has not been completely formed at this point. Added pressure by ram 20 forces the slug to fill cavity 46 and spread filling the shaped wall of guide 32. This forms the semi-finished assembly.

As the next step in the sequence, ram 20 is retracted to the position shown in FIG. 1. Spring 26 now elevates the guide and clamp member 24 back to the FIG. 1 position out of contact with the partially formed rivet and the parts 34 and 36. In view of the outward flare of the discharge section 32 which may flare outwardly at an angle of about 15.degree. from the vertical, the partially formed rivet does not bind to the guide and clamp member and prevent its retraction. The turntable-mounted anvil 38 is automatically advanced to the rivet completion station.

As shown in FIG. 3, the partially formed rivet now has the configuration designated by reference numeral 18'. At the rivet completion station the partially formed rivet is indexed beneath a ram 48 which is positioned within a support 50 to enable vertical reciprocating movement of the ram. The working face 52 of the ram is contoured to the configuration of the upper cap desired upon the rivet. Ram 48 is now driven down onto the partially formed rivet 18' to further deform this member into the configuration of the completed rivet shown by reference numeral 18" in FIG. 4. As seen in this figure, at the completion of the final riveting step, caps are formed on both ends of the rivet and the rivet has expanded to completely fill the holes in the parts 34 and 36.

Upon retraction of ram 48, the turntable is advanced to a discharge station at which the riveted parts are removed and deposited, for example, upon a conveyor for transfer to a further assembly system. The anvil 38 is now returned to the part feed station to commence another cycle of operation.

As will be appreciated by those skilled in the art, suitable control means for controlling the above disclosed sequence of operations including prearranging a suitable timing sequence and signals to indicate when one operation has been completed and when to commence the next step are now well known in the art and thus specific disclosure of such devices in the present specification is unnecessary.

While a presently preferred embodiment of the invention has been shown and described with particularity, it will be appreciated that various changes and modifications may readily suggest themselves to those of ordinary skill in the art upon being apprised of the present invention. It is intended to encompass all such changes and modifications as fall within the scope and spirit of the appended claims.

Claims

What is claimed is:

1. A method for riveting parts together comprising placing superimposed parts onto an anvil, said parts having rivet-receptive holes in substantial alignment, said anvil portion in alignment with said holes being capable of forming a rivet head, forcing a slug through a restricted orifice of smaller diameter than that of the slug into the substantially aligned holes in said parts from the side opposite the anvil, and utilizing the pressure generated in forcing the slug through said orifice to clamp said parts to the anvil, and then forcing said slug into engagement with said anvil portion and deforming both ends of said slug to thereby rivet the parts together.

2. A method according to claim 1 which includes the step of forming cap means on the forward edge of said slug.

3. A method according to claim 1 further comprising providing the hole in the part most distal from said anvil with a larger diameter than the holes in the other parts joined and deforming a portion of said slug outwardly into the larger hole to lock the parts to each other.

4. A method according to claim 1 further comprising removing the pressure clamping the parts to each other, and thereafter completing the formation of the slug into a rivet including forming a cap portion on the side of the rivet opposed to said anvil.