US1857754A - Riveted joint - Google Patents

Description

May 10, 1932. f;- w HAlL 1,857,754 l l RIVETED JoNT Filed March 26, 1925 INVENTOR A TTOR/VEY Patented May 10, 1932 UNITED lCHARLES WARD HALL, OF LARCHMONT, NEW' YORK RIVE'IED JOINT Application flled March 26, 1925. Serial No. 18,542.

The forms of riveted joints have long been standardized, andin all of them the material, proportionsand pitch of the rivets, which are subjected chiefly to shearing stress, are

5 determined accordlng to well-established specifications. The rated eiiiciency of the various forms of' the joints ranges all the way from a minimum of about 50 per cent., for a single-riveted lap-joint, to 94 per cent.

l in the case of a quadruple-riveted butt-joint, the utmost attainable in lap-joints being 67 per cent.

The object of my present invention is to improve upon the established practice in l joints of this typeand, by increasing their eliiciency, to reduce both the weight and the cost ofl the jointed structure.

To this end the invention consists, briefly, in forming the rivet-holes in the bottoms of conical offsets or countersinks stamped in the plates, and to rivet together the two plates with the projections on one nested within the depressions in the other.

In the joint thus formed the shearing stress is practically all transferred from the rivets to the flanged edges of the holes, while the rivets are subjected to little if any additional longitudinal tension in holding the plates clamped together. As a result, the sectional area of the rivets required for a given joint being reduced, either smaller rivets may be used or, as is preferable, they may be given a greater pitch or be arranged in fewer rows. Furthermore, I am able not only to produce presenting a smooth surface on one side due to the countersinking of the rivet heads in the depressions in one of the two plates, a result which in the case of very thin yplates or sheets could not otherwise be obtained.

Several forms of my improved joint are shown, by way of illustration and not of limitation, 1n the accompanying drawings, in which- Figure 1 is a view showing, in longitudinal section, a double-riveted lap-joint embodying my improvements; Fig. 2 is a plan view of the bottom or inner side of the same; Fig. .3 is a sectional view, similar to Fig. l, show- 0 ing a modified lform of the joint; Figs. 4

lap-joints of 100 per cent. efficiency but j oints view of a broken length of spiral riveted pipe showing the application thereto of a singleriveted lap-joint embodying my improvements.

Referring first to Figs. l and 2, a and b indicate the two plates, or plate sections, and c indicates a cover strap used in connection with the inner of the two rows of rivets d and c, by which the plates are joined. The rivets of the inner row are set in holes d1 a formed in the bottoms of the conical offsets or countersinks al, b1 and c1 which are stamped out in the respective plates and form as it wereconical anges around the rivetholes, and in which are nested the projections ofthe lower plate within the the depressions formed in the upper plate and the projections of this upper plate within the depressions formed in the cover. The rivets of the outer row are similarly set in holes e1 formed in the bottoms of a second row of conical offsets or countersinks a2 b2, which arc formed and nested together in the same way. In both rows the headed ends of the rivets are countersunk in the conical depressions formed in the lower side of the bottom plate.

As a matter of' practice, the offsets and concentric rivet holes will usually be punched in both plates, and in the cover, at a single operation in a suitable press, which should form the offsets slightly in advance of the rivet-holes since, if the rivet-holes are formed first, the off-sets will be split around the edges of the holes and so weakened. A depth for the conical depressions of from two to three times the thickness of a plate will be Vfound to give satisfactory results and is recommended. The size and pitch of the rivets, and hence of the rivet-holes, will depend largely upon the angle which is given to thel conical depressions and projections formed in the plate around the holes. Inasmuch as the smaller this angle the less the force required to 'maintain the joint, asthe angle decreases and the walls of the offsets approach parallelism the smaller will be the test their diameter of the rivets which may be used or in very ductile material such for instance as `duralumin immediately afteroquenching or soft annealed steel, may be nearly parallel. For plates of less ductility the angle will usually vary from the neighborhood of 80 up to about 110 degrees. A preferred way of determining the most economical riveting for plates of non-standardized material is to ductility for the offsetting operation b y successive trials and to adopt the offsets with the steepest sides, or having the smallest conical angle, to which the material can be formed without developing incipient cracks. As the angle approaches Zero and the walls parallelism, the outer end or tip of the body of the punch should be of one-fourth to one-half larger .diameterthan the rivets so as to form at the bottom of the depressions an annular projection or shoulder around the,

rivet-hole over which to upset the rivet-head. In the joint here illustrated, the angle of the conical Walls of the depressions and offthickness of each and the rivets, of a diamsets is 72 degrees,

and one-half times the eter .equal to two and a short pitch respectively of five and three times such diameter. AThis joint, with rivets of' the same material as the plates, hasa 100 per cent. efficiency, or, Without the cover strap shown, cent.; whereas, the specifications for a stand ard double-riveted lap-joint, in which as stated the highest efficiency attainable is 67 per cent., call for rivets of a diameter two and three-fourths to three times the plate thickness and set at along pitch of only three and one-fourth diameters. I therefore obtain with less than tivo-thirds the number and sectional area of rivets a joint of greater efliciency than that vheretofore attainable.

In the modified joint shown in Fig. 3, the conical offsets al and 721 around the inner row of rivet holes are reversed, being lpunched out from the upper tothe lower sides of the plates so as to project in the opposite direction to the ofsetsa2 and Z22 of the outer row, and the rivets l used therein are countersink, instead of button-head, rivets. By this modification I obtain, without the aid of any cover strap, a joint of 100` per cent. efficiency.

In the triple-riveted lap-joint ofFigs. 4 and 5, the angle w1 of the conical offsets al a2 1.3, etc., around the rivet holes is shown as of 1 90 degrees, and the rivets have, as shown, a

diameter equal to three times the plate thickness. The short pitch of the three rows of rivets d e and f is four times the rivet diam,- eter, while the long pitch of the rivets is the same in the middle row and twice as great, or

plate, have a long pitch an efficiency of 76 per eight times the rivet diameter, in the inner.

and outer rows. Individual cover caps 02, with conical offsets c3, are here used in connection with the inner row of rivets in place of the continuous cover strap shown in the double-riveted joint already described. Here again the joint produced has an efficiency of 100 per cent.

For spiral pipe, where as is well known the strain upon the rivets is much less than in pipe with longitudinal riveted joints, the single-riveted joint illustrated in Fig. 7, with rivets Z set in` holes surrounded by nested offsets b5 in the overlapped edges a4 b4 of the spiral plate, produces a pipe of' high strength, to approach which a double-riveted joint would be required according to the present standard practice.

It will of course be understood that the invention is applicable to butt-joints as well as to lap-joints, and that the details of the joint may be variously modified without departing from the spirit or sacrificing the substantial advantages thereof-for instance, While a circular conic frustum isy shown as a con-I venient form for the offsets, they may have other than circular sections and may also be inclined so as to present a more nearly lperendicular face on one side than on the other.

What I claim as new, and desire to secure by Letters Patent, is-

1. In a joint of the type described, the combination, of two plate sections and a cover superimposed one on another and rivets set in holes formed in the bottoms of conical offsets which are stamped in the two plate sections and in the cover and are nested together the projections on one plate section within the depressions of the second plate section and the projections of thev second plate sec tion within the depressions in the cover, the

heads formed on the ends of the rivets being CHARLES WARD HALL.

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