US776758A - Boiler-seam. - Google Patents

Description

No. 776,758. y 1 PATENTBD DBG.6,1904.

. G. H. RHBU'TAN.

BOILER SEAM.

APPLIGATION FILED APR. 14. 1904.

vNo MODEL.

No. 776,758. Patented December 6, 1904.

UNITED STATES PATENT OEETCE.

GARRETT H. RHEUTAN, OF BOSTON, MASSACHUSEITS, ASSIGNOR OF ONE- .HALF TO ROBERT B. LINCOLN, OF VALTHAM, MASSACHUSETTS.

SPECIFICATION forming part of Letters Patent N o. 776,758, dated December 6,` 1904. Application iled April 14, 1904. Serial No. 203,194. K (No model.)

T @ZZ 10771077@ may @OwW/b: A seam of the above character exhibits a 5o Be it known that I, GARRETT H. RHEUTAN, strength considerably above that of the ordiot Boston, in the county of Suiiolkand State nary lapped seam and equal to or exceeding' of Massachusetts, have invented certain new the usual forms of butt-seams employing reand useful Improvements in Boiler-Scams, ot' intorcing straps, plates, or welts, besides bewhich the following is a speciiieation. ing much lighter, `flexible, and less expensive This invention relates to riveted seams ot' than the last said seams and capable of being steam-boilers and other pressure vessels or subjected to the action oll the lire without structures subject to tensile strain; and it has danger. My seam may be employed in conxo for its object to attain greater strength in nectienwith ordinaryroundabout-seams,ifdelapped seams than has heretofore been obtainsiredw-that is, by bending up single plates into able, thereby providing a form of joint. which the form of short cylindershavinglongitudinal affords to the structure adegree ol strength joints constructed aecordingtomyinvention, a which has been obtainable only by the use of number oi" these short cylinders being riveted I5 bulky and cumbersome butt or strap seams, together by roundabout-joints to form a coman increased degree of elasticity, less weight, plete drum or shell. lt is permissible, howand a less-expensive form of construction. ever, and in general preferred to do away ln steam-boilers this seam may be placed with the roumlabout-seam and run the plates nearer' to the fire than a butt or strap seam lengthwise ot' the boiler, as indicated in Fig.

2o without danger, and its use dispenses, it' de l. This gives a much lighter and more liexisired, with the roundabout-seams heretofore ble boiler, and although the seams 19. may be employed in boilers. more or less subjected to the action of the The invention applies particularly to the fire there will obviously be a smaller number outside shells or similar parts otl boilers,which ot' rivets directly in the iiame than would be 2 5 are subjected to a tensile strain tending to the case with a number ot' seams occurring pull the edges of the plates apart at the seam. on the bottom et' the boiler.

Of the accompanying drawings, Figure l As is well known to those skilled in the art, represents a side elevation of the shell er drum certain requisites must be observed in making el: a boiler or similar pressure vessel provided a riveted seam whose strength shall be the 30 with a seam constructed kaccording' to my inmaximum obtainable with the particular devention. Fig. 2 represents a transverse secsignet seam and the minimum amount of ma- 8O tion thereof. Fig. 3 represents an enlarged terial, and among these requisites are, lirst, view of one of the units or angles of the seam a certain proportion between thickness of with the rivets in section. plate and diameter ot' rivet-hole. Thus with y 35 The same reference characters indicate the a boilerplate of .375 inch thickness the same parts in all the iigures. rivet-holes should be about .78 inch in di 85 Tn the. drawings, l0 is a cylindrical shell ameter. A second requisite is to have the made up of plates 1l l1, having overlapping shearing strength et' the rivets in the seam edges riveted together and forming lengitudisubstantially equal to or somewhat exceeding 40 nal seams or joints 12. The rivets 13 are arthe tensile strength of a thickness of plate,

ranged in two parallel zigzag lines or rows since otherwise the rivets would give way to composed of a series of arched units, one of a strain before the plates would do so. Calwhich is enlarged in Fig. 3, the units preferculation will show that ii" this second requiably forming substantial right angles, as site be preserved in a straight lapped seam 45 shown. l prefer also to form the edges lt ot' having a single line olI rivets the minimum the boiler-plates in zigzag or sinuous lines pitch 'for the above given dimensions olE plate 95 parallel to the lines of the rivets, as this saves and rivet would be about 1.75 inches, and the material Without sacrificing strength and instrength of metal remaining in the plate in creases the flexibility of the seam. any cross-section et' a zone extending longitudinally of the direction of greatest tension can never exceed about 55.5 per cent. of the strength of a similar unperforated section of plate. If such a seam be double-riveted, a maximum strength of about 68.5 per cent. of that of the plate may be obtained. A third requisite is that the callring pitch must not exceed acertain maximum amount beyond which the plates would have a tendency to bow between the rivet when calked. This maximum pitch for the thickness of plate above assumed-namely, .375 inchwould be about 2.5 inches.

Tn the above calculations a tensile strength of plate of sixty thousand pounds to the square inch and a shearing strength of rivet of fortysix thousand pounds to the square inch has been assumed.

Examining Fig. 3, which represents a single unit of the joint, it is evident that the greatest strain or tension is exerted in lines which are parallel to a zone or parallel-sided strip of the shell extending vertically of the paper and having a width t The theoretical lines of fracture are therefore in general parallel to a b. Let it be assumed that the distance a b is equal to 17.5 inches, the thickness of the plates .375 inch, the diameter of rivet-holes .7 8 inch, he maximum calliing pitch between centers of rivets 2. 5 inches, and the lap of the plates 4. 25 inches. The strength of the joint along various lines of possible fracture may then be examined. Along the lines co b and c CZ the metal removed by a single rivet-hole amounts to 4.46 per cent. of the total section of the plate along this line, and the strength of the plate along said line is therefore 95.54 per cent. of the strength of a similar section of imperforate plate. If a similar calculation be made for the fractureline e f, it will be found that the total amount of linear inches of the two plates remaining after abstracting the diameters of the four rivet-holes crossed by this line amounts to about 18.5, which is obviously more than one hundred per cent. of the metal in the shortest imperforate section of the zone, such as a b. Similarly, it will be found that the strength of double plate along the line g it z' amounts to about 99.7 per cent. of the strength of the imperforate section a b. By a like process it will be found that the percentage of strength of the plates along any other fracture-line between lines a I) and c ci' is in excess of the strength along either of said lines a Z) or c d. The weakest fracture-line (there being two such fracture-lines in this instance) is therefore that which includes the smallest number of rivets. Thus the upper line L Z2 includes one whole rivet and the lower line c Z two half-rivets. Since there must be in any riveted joint at least one unsupported rivet for each unit along any fracture-line, it is evident that by the construction described I am enabled to make the joint of a strength corresponding to a fracture-line taken through single rivets pertaining to units of a length considerably increased over that heretofore attainable.

It will be observed that the number of rivets shown in Fig. 3 in the unit zone is twenty. Vith the dimensions of parts and strengths of materials hereinbefore assumed the aggregate shearing strength of the rivets therefore equals that of 19.32 inches of plate, so that the second requisite, as well as the other two requisites before referred to, are satisfied by the construction of my improved joint. It will be understood that the invention is not confined to the dimensions nor to the exact spacing, arrangement, or number of rivets per unit herein given. The construction of the joint is such that by increasing or decreasing the number of rivets in each unit by adding rivets to or subtracting them from the base of the pyramid or triangle the percentage of strength of the joint may be increased or diminished. This is equivalent to saying that the strength of the joint increases as the relative length of theiunits increases, and vice versa.

Itis apparent that the serration of the edge of at least one of the overlapping plates is an important feature with respect to the calking of my improved form of joint applied to a pressure vessel. The apex rivets of the several units are too far apart for proper calling if the edge of the plate is made a straight line, and accordingly the plate whose edge is to be calked is made to follow the line of rivets nearest its edge in order that the plate may be calked without bowing between rivets. In general the outer plate, such as the one whose edge is uppermost in Fig. 1, is the one to be calked.

I claim- 1. A pressure vessel having a pressure-retaining wall including a pair of overlapping main shell-plates subject to tensile strain, and a zigzag series of rivets connecting the margins of said plates, the arrangement being such that the weakest fracture-line of the joint is that which includes the least number of rivets.

2. A pressure vessel having a pressure-retaining wall including a pair of overlapping main shell-plates subject to tensile strain, and a zigzag double row of rivets connecting the margins of said plates.

3. A pressure vessel having a pressure-retaining wall including a pair of overlapping plates subject to tensile strain, and a zigzag series of rivets connecting the marginal portions of said plates, said portions having sinuous edges substantially parallel to the line of the rivets.

4. A boiler or other pressure vessel comprising a plurality of longitudinal plates form- IOO IIO

ing an outwardly-convexed tubular shell and having longitudinal overlapping margins connected by a zigzag line of rivets.

5. A riveted lapped joint comprising overlapping main wall-plates subject to tensile strain and connected by a series of rivets arched across a zone extending longitudinally of the direction of greatest tension, the weakest fracture-line of the joint 'being that which includes the smallest number of rivets.

6. A riveted lapped joint comprising overlapping main wall-plates subject to tensile strain, and an angular series of rivets arched across a zone extending longitudinally of the direction of greatest tension, said series consisting of rivets at the apex and ends of the arch and intermediate rivets along the sides thereof.

7. A riveted lapped joint comprising overlapping main wall-plates subject to tensile strain, a row of rivets next the edge of one of said plates arched across a Zone extending longitudinally of the direction of greatest tension, and a second row oi' rivets arched across said Zone and substantially parallel to the iirst said row.

8. A pressure vessel having' a pressure-retaining wall including a pair of overlapping main shell-plates subject to tensile strain, a zigzag row of rivets connecting said plates and having apex rivets at a greater distance apart than the proper calking pitch, and a sinuous callied edge portion on one of the plates following the line of rivets, substantially as described.

In testimony whereof| I have aiiixed my signature in presence of two witnesses.

GARRETT H. RHEUTAN.

Witnesses:

R. M. PiERsoN, A. C. RATIGAN.

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