US3055255A - Blind rivet with internal mandrel supporting element - Google Patents

Description

Sept. 25, 1962 E. J. BURRELL 3,05 I

BLIND RIVET WITH INTERNAL'MANDREL. SUPPORTING ELEMENT 5 Sm les-Sheet -1 M 24, l 58 Filed arch 9 2 5 1 I Sept, 25, 1962 'E. J. BURRELL BLIND RIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958 5Q Sheets-Sheet 2 Sept. 25, 1962 E. J. BURRELL BLIND RIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958 5 Sheets-Sheet 3 BLIND RIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958- Sept; 25, 1962 E. J. BURRELL 5 Sheets-Sheet 4 P 1962 E. J. BURRELL BLIND RIVET WITH INTERNAL MANDREL SUPPORTING ELEMENT Filed March 24, 1958 5 Sheets-Sheet 5 United States Patent 3,055,255 BLIND ET WITH INTERNAL MANDREL SUFPURTENG ELEMENT Edward James Burr-ell, Woodiey, England, assignor to Avdel Limited, a British joint-stock company Filed Mar. 24, 1958, Ser. No. 723,497 Ciaims priority, application Great Britain Mar. 25, 1957 7 Claims. (Cl. 85-40) This invention relates to blind riveting in which tubular rivets are expanded or clinched into position in the work pieces to be riveted by pulling a mandrel therethrough, especially to blind riveting by means of a mandrel that is itself non-deformed in the clinching or expanding operation, as is essential in blind riveting by means of a magazine type gun in which the stem of a non-deformable mandrel carries a supply of tubular rivets threaded thereover.

The present invention has for an object to provide improved riveting with a tubular rivet and mandrel both so shaped as to ensure effective clinching of sheets.

In accordance with the invention, a high clench headed tubular rivet which may be upset with a broaching mandrel has a shank formed with a relatively strong zone at or near its tail and with a relatively weak zone intermediate its head and the strong zone.

Preferably the strong ZOne is constituted as an external flange or thickened wall at or near the tail of the rivet. The weak zone may be formed by making the wall of the rivet bulbous, or slotting it or thinning it.

In accordance with another feature of the invention, the headed tubular rivet may be formed with an internal conical lead-in to the weak zone.

According to another aspect of the invention, a high clench headed tubular rivet which may be upset with a broaching mandrel has a shank which is formed with a reinforcing flange at or near its tail end and also, at least at that part thereof which when the rivet is first inserted in the registering apertures formed in two or more members to be riveted together lies between said reinforcing flange and the members, with a relatively weak zone which is capable of expansion under longitudinal pressure from the mandrel less than that required to expand the reinforcing flange.

The formation of the shank so as to be capable of such expansion may be effected in various ways; for example, the rivet may have a parallel bore and be longitudinally weakened by slitting or otherwise at at least two places spaced from one another around its circumference, or it may be formed with a waist, the wall thickness of which is preferably less than that of the remainder of the shank.

The rivet may be used with a mandrel the stem of which is a friction fit within the rivet.

In addition, the dimensions of the rivet and the mandrel used therewith are preferably such that in finally passing through the shank the latter as well as the reinforcing flange at its end is expanded thereby.

In accordance with a still further feature of the invention, the head of the mandrel where it joins the stem is of substantially hemispherical shape rather than conical to assist in the expansion of the shank and tight clenching before the reinforcing flange is expanded.

Alternatively, the head of the mandrel where it joins the stem may be conical but of greater included angle than is appropriate for rivets without a reinforcing flange as set forth above, the included angle being dependent upon the axial thickness of the flange, said thickness being reduced as said angle is increased.

Five constructions of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIGURE 1 is a view in sectional elevation of one emice bodiment of a rivet in accordance with the invention.

FIGURE 2 is a view in elevation of a mandrel employed with the rivet in accordance with the invention.

FIGURE 3 is a view in elevation of the rivet threaded on the mandrel and inserted into registering holes in the work to be riveted.

FIGURE 4 is a view in elevation of the rivet mandrel assembly showing initial expansion of the rivet.

FIGURE 5 is a view in elevation of the upset rivet and of the mandrel pulled therethrough.

FIGURE 6 is a view in sectional elevation of a rivet constructed in accordance with another embodiment of the invention.

FIGURE 7 is a view in sectional elevation showing the rivet as illustrated in FIGURE 6 threaded over the mandrel and inserted in apertured holes in the work to be riveted.

FIGURE 8 is a similar View to that of FIGURE 7 illustrating the initial expansion of the rivet after the initial pull on the mandrel.

FIGURE 9 is a view of the upset rivet and of the mandrel pulled therethrough.

FIGURE 10 is a plan view of FIGURE 9.

FIGURE 11 is a view partly in section of another embodirnent of the invention.

FIGURES 12 to 16 show progressive stages of rivet breaching employing the rivet and mandrel as illustrated in FIGURE 11.

FEGURES 17 and 18 are views in elevation of another embodiment of the rivet.

FIGURE 19 is a view similar to that of FIGURE '17 except that a split ring is inserted in the rivet head counterbore.

FIGURE 20 is a cross-sectional plan view on the line X-X of FIGURE 19.

FIGURE 21 is a sectional view of a modified form of the invention.

Referring to FIGURES l5 of the drawings, a parallel bore rivet l is formed with a head 2 at one end of its elongated shank 3 and with a reinforcing flange 4 at its other end. P our circumferentially spaced axial incisions 5 formed in the shank 3 are of such length and so located lengthwise thereof that when the rivet 1 is placed in the hole 6 in the sheets 7 and 8 to be riveted, said incisions 5' extend for a short distance into said hole 6. These incisions 5 adapt the portion of the shank 3 protruding from the remote side of the sheet 8 to expand during the broaching operation as will be later explained. The rivet 1 is threaded tail first over a mandrel 9 having a stem 16 the diameter of which is only slightly smaller than that of the internal bore of the rivet 1 so that the rivet 1 is a close sliding fit on the stem 10 of the mandrel 9. Where it joins the stem 10 the head 11 of the mandrel 9 is of semicircular longitudinal cross-section or has a semi-spherical outline as indicated at 12. It will be observed that the diameter of the flange 4 of the rivet 1 is slightly smaller that that of the registering holes 6 in sheets 7 and 8 to be riveted so as to provide sufficient clearance for the mandrel 9 and the tail end 4 of the rivet 1 to pass through the holes 6. The free end of the mandrel stem 10 is inserted in a known riveting gun or appliance, the head 2 of the rivet 1 bearing against the front jaws (not shown) of the gun which act as an anvil against which the rivet head 2 bears during breaching as the rivet 1 is expanded.

In use the rivet 1 threaded over its mandrel 9 is inserted in apertured holes 6 in sheets 7 and 8 (FIG. 3), the initial pull on the mandrel 9 during breaching causes the rivet shank 3 to expand around the area where the shank 3 is weakened by the incisions 5. Actually the portion of the shank 3 expands into a lantern shape as can be seen from FIGURE 4. Upon completion of this expansion the mandrel 9 continues to pull the flange 4 of the rivet 1 into abutment with the sheet 8. After this has taken place the mandrel 9 continues to pull the sheets 7 and 8 together. When the sheets are tightly clamped the increased force on the mandrel 9 now expands the reinforcing flange 4 and clears the head 11 of the mandrel 9 through the rivet bore and so expands the rivet shank material thus radially filling the holes 6 in the sheets 7 and 8, and at the same time further longitudinally constricts the rivet shank 3. This results in additional clench of the sheets 7 and S. It should be emphasized that the bore of the rivet 1 should be a close sliding fit on the stem 18 of the mandrel 9 otherwise the expansion of the rivet shank 3 would not be uniform and not in axial alignment. The mandrel 9 for placing the rivet 1 has a specially designed head 11 which is substantially spherically shaped at its junction with the stem 1t so as to give maximum end loading. It will be understood that this rivet method employs a mandrel with a thicker stem than is usually employed in magazine type riveting guns thereby lessening the chances of mandrel breakage and at the same time permitting a greater degree of clench.

In the modification of the invention as illustrated in FIGURES 6 to the shank 3 of the rivet 1 is formed with a bulge 13 in that part of the shank which is adapted to form the tail. This bulge 13 is formed by expanding a portion of the shank of an initially parallel bore rivet, for example by hydraulic means, until the bulge 13 reaches an external diameter such as just to pass through the holes 6 in the sheets 7 and 8 to be riveted. For example, for riveting holes of A" diameter the external diameter of the bulge 13 would be approximately .248. The formation of the bulge 13 causes a reduction of the wall thickness of the shank '3 at the locality where the bulge 13 is formed so that this area when subjected to longitudinal pressure becomes easily expansible. As can be seen from FIGURE 7 the bulge 13 extends from approximately the remote side of the farmost sheet 8 to be riveted in the direction of the reinforcing flange 4 of the rivet 1 and becomes more pronounced midway between the farmost sheet surface and the reinforcing flange 4 leaving a non-deformed portion 13a of the shank between the flange 4 and the bulge 13. The initial pull on the mandrel 9 causes the bulge 1-3 to spread outwardly; at this time the bulge 13 cams the sheet 8 into closer contact with sheet 7. An increased pull on the mandrel 9 brings the reinforcing flange 4 into engagement with the bulge 13 forcing it to collapse as shown. Then the mandrel 9 continues to pull the sheets 7 and 8 together.

The rivet illustrated in FIGURES 11 to 16 is a further development of the tubular rivet shown in FIGURE 7. In this embodiment of the invention the elongated shank 15 of the rivet 14 has both a bulbous configuration 16 and a neck 18 intermediate its length, The bulge 16 joins the reinforcing flange 4 at the tail end of the shank 15 by a short parallel portion 17. At its opposite end the bulge 16 merges into the neck portion 18. A diverging conical shank portion v19' joins the neck 18 with a rivet head 20 which is counterbored at 21 to give relief to the broaching mandrel 22 as will be later explained. The rivet 14 is threaded over the mandrel 22 which has a cylindrical head 23 tapering at towards the junction with its stem 24. As illustrated in FIGURE 11 the concal portion 25 of the mandrel 22 diverges from its stem 24 at a point 24:: towards the head 23 so that its faces 25 form an included angle of approximately 60". This angle may vary, the magnitude of the angle depending upon the axial thickness of the reinforcing flange 4 of the rivet 14.

In use the mandrel 22- with the rivet 14- threaded tail first thereon is loaded into the gun and the rivet mandrel assembly is inserted into the hole 6 of the work 7 and 8 to be riveted. During breaching operation the mandrel head 23 sinks into the reinforcing flange 4 of the rivet (see FIGURE 13) causing the reinforcing flange 4 to work harden and to increase its resistance to further expansion radially. As continuous pull is applied on the mandrel 22 the bulged portion 16 yields first to the pressure on the flange and causes the bulge 16 to collapse and expand radially as can be seen in FIGURE 14. Subsequent pull on the mandrel overcomes the resistance to expansion offered by the reinforcing flange 4, and the mandrel head 23 expands the flange 4 and the shank 15, which lies within the rivet hole 6 in the work 7 and S, radially (see FIGURE 15) so that when the mandrel 22 is pulled through the rivet 14, the material of the rivet shank 15 fills the 'hole 6 completely. The formation of the counter bore 21 in the rivet head 20 prevents the extrusion of the surplus rivet material which has been shifted axially by the moving mandrel head 23. The surplus material of the inner Wall of the rivet shank 15 is flattened out by the passing of the head 23 of the mandrel 22 therethrough, thus providing a parallel bore capable of receiving a sealing pin if required. It has been found that any undesirable extrusion of rive-t material has been eliminated by the formation of a counter bore in the rivet head and of the constricted portion or neck on the shank thus resulting in perfect clenching of the work to be riveted.

The purpose of the reinforcing flange 4 is to prevent the mandrel 9 or 22 from expanding the tail end of the rivet shank until the collapse of the weakened zone 5 or 13 or 16 has been effected.

It will be understood that the bulge of the rivet shank can be weakened by reducing its wall thickness in order to induce an early expansion or collapse.

Furthermore, the hardness of the reinforcing flange 4 of the rivet 14 may be increased by work hardening, so that additional pressure would be required on the mandrel 9 or 22 to expand the flange 4.

The proposed method of manufacturing the rivet illustrated in FIGURES 11 to 16 is to form external dimensions, drill, ream and part off, then anneal and hydraulically form the bulge.

In the modification \of the invention as illustrated in FIGURES 17 and 18 a tubular rivet 26 has an elongated parallel'shank portion 27 of uniform wall thickness which merges into a conical portion 28 joining the shank portion 27 with a reinforcing flange 29 at the tail end of the rivet 26. The rivet 26 is formed with two coaxial parallel bores '36 and 31, the bore 39 extending from the head of the rivet 26 being of a larger diameter than the bore 31. The bore 30 tapers at 32 in the direction of the bore 31. It has been found by tests with rivets having A" shank diameter that the'most suitable angle of inclination of the conical portion 28 relative to the axis of the rivet is approximately 19.

Preferably the wall thickness of the conical portion 28 of the rivet 26 is approximately greater than that of the parallel shank portion 27 and in no case is it less than the actual thickness of this parallel portion.

The design of this rivet is based on the same principle as that described with reference to hydraulically preformed rivet illustrated in FIGURES 11 to 16, namely the controlled collapsing of a weakened wall section of the rivet. The complementary mandrel is similar to that shown in FIGURE 11. The reinforcing flange 29 consti-tutes the strong zone, and the conical portion of the shank 28 and that part of the parallel shank portion 27 protruding at the inaccessible side of the sheets 7 and 8 to be riveted the Weak zone, or the collapsible part of the rivet upon the initial pull of the mandrel 22.

The rivet 26 just described does not require to be hydraulically preformed. The manufacturing costs of this rivet are, therefore, more economical than those illustrated in previous examples. The rivet 26 is produced from cylindrical stock of metal by turning the shank portion 27 and the reinforcing flange portion 29, cutting an annular groove 33 and thus forming the conical portion .23; drilling a hole to a diameter equivalent to that of bore 31, parting the rivet from the stock and counterboring the rivet hole 31 to the size of diameter 30 and finishing the rivet. For example when rivets 26 are made from AL 69 alloy it has been found to be advantageous to treat the rivets in a solution of neutral salts for 15 minutes at approximately 490 C. plus-minus and subsequently plunge the rivets into cold Water. Age hardening is completed after approximately 5 to 10 days imparting necessary strength to the rivets.

It will be understood that rivets above described may be made from other materials, for example B.51 SO aluminium alloy; Monel DTD 200A G & C; brass 70/ 30,

etc. Prior to broaching it is preferred to lubricate the rivet or the mandrel. This may be effected in various ways.

Furthermore it may be preferable to use bar material in a semi hard condition to facilitate machining, but such rivets will require an annealing operation in order to assist collapse of the rivet shank during riveting.

The construction of the rivet and mandrel assembly described above may be advantageously employed in magazine type riveting tools.

The bulbous portions 13 and 16, FIGURES 6 and 11 respectively, of the rivet shank are preformed hydraulicwy, and the stem 24 of the mandrel 22 is a sliding fit within the bore of the rivet at two localities. In the construction of the rivet shown in FIGURES 17 and 18 however, the mandrel stem 24 is a sliding fit only within the bore 31 of the reinforcing flange 29 of the rivet 26. The remainder of the rivet shank is not supported by the mandrel stem 24 and in consequence the rivet 26 may become out of alignment with the central line of the mandrel. This causes an uneven collapse of the tail of the rivet during broaching. To overcome this drawback a split ring 33 of soft material may be inserted in the counterbore 31 of the rivet head 32 (FIGURES 19 and 20) for the purpose of centralising the mandrel 22 in the rivet during broaching.

In use a number of rivets 26 and split rings 33 threaded tail first on the mandrel stem 24 are inserted in a magazine type riveting gun. After the rivet is expanded the ring 33 in each rivet 26 is retained on the mandrel upon the upsetting of the rivet until the return stroke of the riveting gun (not shown) when the ring 33 is ejected by a succeeding rivet 26. This requires very little effort due to the split in the ring 33.

In the modification shown in FIGURE 21 the reinforcing flange 29 at the tail of the rivet 26 may be formed with a small cylindrical protrusion 34 which projects into and is located in the counterbore 30 of the adjacent rivet 26.

It should be noted that with snap head rivets the possibility of misalignment during broaching is quite remote as the front jaws of the gun form sufficient bearing surface. With the countersunk head rivets, however, the gun jaws offer insuflicient bearing surface and it is necessary to provide some form of axial control.

I claim:

1. In combination, a high clench headed tubular rivet and a broaching mandrel, said tubular rivet comprising a head, a shank, and a flange, said head, shank and flange portions having concentric longitudinal bores, said shank having a main substantially cylindrical portion and a frusto-conical portion connecting said main portion to said flange, the latter portion having a periphery which progressively reduces in progressing from said shank main portion to said flange, said flange extending peripherally outwardly of said latter portion and having a radial thickness substantially greater than the Wall thickness of said latter shank portion, the bore in said flange being of lesser size than the bore in said shank and said head, said mandrel having a shank received in and extending longitudinally through said head, shank and flange, said mandrel having a shank formed complementarily to the periphery of said bore in said flange, said mandrel having an enlarged head of larger size than said bore in said flange and connected to the mandrel shank by a section tapering from the periphery of the head to that of the mandrel shank, the head being of a size to be freely slidable lengthwise through at least the major portion of the length of said shank, said mandrel shank being slidable in said flange bore, said mandrel head and tapered portion being initially positioned to the other side of said flange with respect to the shank portion of the rivet, and guide means frictionally mounted within said longitudinal bore extending through said shank of said rivet comprising a centering means for said mandrel and having a bore concentric with said bore in said flange and slidably receiving said mandrel shank, the bore in said centering means being of a size smaller than the periphery of said head of said mandrel, the latter means being slidable outwardly of said rivet, when the mandrel is drawn through the rivet.

2. The combination of claim ,1 wherein said centering means comprises a split sleeve.

3. A tubular rivet for use in blind riveting operations Where a mandrel with an enlarged head is drawn through the rivet from the tail end thereof to the head end thereof and expands portions of the rivet, said rivet comprising a head, a shank, and a reinforcing flange, said head being connected to one end of said shank and said reinforcing flange being connected to the opposite end of said shank, said shank, said head, and said reinforcing flange having concentric longitudinal bores, said shank having a first portion and a second portion connected to said first portion, said first portion being positioned adjacent said flange and connected thereto, said second portion being intermediate said first portion and said head, said second portion being of larger internal diameter than that of said flange and larger than the diameter of the head of said mandrel, said first portion being formed of a substantially uniform wall thickness and having a bore which decreases in diameter from the internal diameter of said second portion to the internal diameter of said flange, said flange having a wall thickness substantially greater than said first portion and extending radially outwardly of the adjacent end of said first portion, the bore of said flange being sufficiently large to receive the shank of said mandrel but smaller than the head of said mandrel, an annular member frictionally mounted within the longitudinal bore of said shank at the head end thereof, said member having a bore concentric with the shank bore and being slidable outwardly of said bore of said shank, said bore of said annular member being of substantially the same size as the bore in said flange, whereby when a pulling force is applied between the shank of the mandrel and the head of the rivet, the head of the mandrel first moves said flange towards the head of the rivet and collapses the shank of the rivet, producing outward bulging thereof, and continued movement of the mandrel effects clenching of the bulged and collapsed shank portions against the parts being riveted, and thereafter the mandrel head passes through said flange expanding the same, and removes said annular member from the head of said rivet.

4. A rivet according to claim 3 wherein the periphery of said first portion decreases progressively from said second portion of said shank to said flange.

5. A rivet according to claim 3 wherein said first portion is of frusto-conical shape with its apex positioned toward said flange and its base toward said second portion of said shank.

6. A rivet according to claim 3 wherein said member comprises a split ring.

7. In combination, a high clench headed tubular rivet and a breaching mandrel, said tubular rivet comprising a head, a shank, and a flange, said head, shank and flange portions having concentric longitudinal bores, said shank having a main substantially cylindrical port-ion and a frusto-conical portion connecting said main portion to said flange, the latter portion having a periphery which 7 V progressively reduces in progressing from said shank main portion to said flange, said flange extending peripherally outwardly of said latter portion and having a radial thickness substantially greater than the wall thickness of said latter shank portion, the bore in said flange being of lesser size than the bore in said shank and said head, said mandrel having a shank received in and extending longitudially through said head, shank and flange, said mandrel having a shank formed complementarily to the periphery of said bore in said flange, said mandrel having an enlarged head of larger size than said bore in said flange and connected to the mandrel shank by a section tapering from the periphery of the head to that of the mandrel shank, the head being of a size to be freely slidable lengthwise through at least the major port-ion of the length of said shank, said mandrel shank being freely slidable in said flange bore, said mandrel head and tapered portion being initially positioned to the other side of said flange with respect to the shank portion of the rivet, and including an annular protruding portion projecting axially from said flange on the side opposite from said rivet shank, said protruding portion having a central bore concentric with and of substantially the same size as the bore in said flange, said protruding portion having an outer periphery formed complementary to said bore in said shank and being adapted to be received in the shank bore of a second rivet to constitute a positioning member.

References Cited in the file of this patent UNITED STATES PATENTS Re. 20,055 'Huok Aug. 4, 1936 927,064 Mower July 6, 1909 2,148,977 Buck Feb. 28, 1939 2,255,650 Burke Sept. 9, 1941 2,384,321 Lees Sept. 4, 1945 2,612,073 Taylor Sept, 30, 1952 2,670,021 Torresen Feb. 23, 1954 2,887,926 Edwards May 26, 1959 FOREIGN PATENTS 737,284 France Oct. 3, 1932 410,423 Great Britain May 17, 1934 982,415 France June 17, 1943 596,275 Great Britain Dec. 31, 1947 613,882 Great Britain Dec. 3, 1948

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