US811861A - Tube-making machine. - Google Patents

Description

PATBNTLD FEB. 6, 1906. G. B. MELLINGER.

TUBE MAKING MACHINE.

APPLIOATION FILED 00T. 20,1904.

4 BHBETJ--SHEET 1.

@Wi/tween@ PATENTED FEB. 6, 17906.

G. B. MBLLINGBR.

TUBE MAKING MACHINE. APPLIUATION FILED 00T. 20,1904.

Wilma/wao 4 BHEETSBHEET 3.

G. B. MELLINGEB.. TUBE MAKING MACHINE.

APPLIUATION FILED oo'r 20 1904 UNITED sTATEs i PATENT OFFICE.

GEORGE Bla-MELLINGER, OF SCOTTDALE, PENNSYLVANIA', ASSIGNOR OF `TWO-THIRDS TO ROBERT SKEMP AND DALE, PENNSYLVANIA.

JOSEPH R. STAUFFER, OF SCOTT- TUBE-MAKING MACHINE.

Specification of Letters Patent.

\ Patented Feb. 6, 1906.

Application filed October 20, 1904. Serial No. 229,348.

vskelp or blank in a manner to 1create a normal tendency of the tube to contract, and thus effectually close the joint or seamV formed by the meeting longitudinaledges of the skelp.

1 Another object is to so organize the apparatus that the various steps may be performed simultaneously at successivepoints of the skelp in order that the manufacture of the tube may be accomplished continuously until a tube of the desired length is completed without lnecessity for the handling of the material, except such vas is necessary to present it to the apparatus.

To the accomplishment of the vrecited objects and others subordinate thereto, the preferred embodiment ofthe invention resides in that construction and arrangement of parts hereinafter described,illustrated in the accompanying drawings, and embraced within the scope ofthe ap ended claims.

In said' drawin s, igire 1 is a side elevation of the comp ete tube-making machine.

' Fig. 2 is a similar view of the machine viewed rolls.

"pair of edge-flexing rolls Fig. 17 is asimilar `from the opposite side. Fig. 3 is a plan view of the same. Fig. 4 is a central longitudinal section on the line 4 4 of Fig. Fig. 5 is a detail view showing the arrangement of the edge-lexing rolls and their relation to the contracting-rolls. Fig. 6 is a detail view of the contracting rolls and their mounting. Fi 74 is a detail view of the mandrel and its rod. Fig. 8 is a .detail view of a modified form of mandrel. Figs. 9 to 15, inclusive, are detail sectional views through the successive pairs of skelp-bending or tube-forming Fig. 16 is a sectional view through a view of a set of contracting-rolls. Fig.,18 is a setional view of the mandrel, showin the -tu e,

form. ig. 19 a section through an advanced expanded thereon to true cylin ricaL portion of the mandrel, showing the manner in which that edge of the tube which was pre.- viously deflected inwardly after the-tube first assumed its normal dimensions is subsequenty deflected or expanded outwardl-yrom a tube of normal dimensions. Fig. 20 is a transverse section of the iinishedtube at a point beyond the mandrel; and Fig. 21 isa detail view of the skelp, showing the effect thereon of the various mechanisms.

Like reference characters designate corresponding parts throughout the views.

. `Since the machine to be described has been especially designed to facilitate the ractice of the method of forming tubes descri ed andclaimed in a divisional application for patent liled by me January 28 1905, Serial N o. 243,057, I will describe the various mechanisms in that order in which they act upon the skelp or blank and will incidentally refer to the method in order that the salient characteristics of the machine may be better under-V stood.

' .In a suitable frame structure, including a base-plate 1 and upri ht boxuides 2, are seven sets or pairs of s {clp-ben ing or tubeforming rolls 3, 4, 5, 6, 7, 8, and 9, disposed in successive arrangement, with the rolls of each pair disposed oneabove another. The shafts 10 of the upper rolls are received by vertically-movable bearing-blocks 11, coperating with head-screws 12 in a manner well understood in the art. Certain of the shafts 13 of the lower rolls are provided with driving-gears 14,. located beyond the bearings and meshing with inions 15,V fixed to studshafts 16, to Whic are also fixed beveled gears 17, meshing with beveled pinions 18 on a driving-shaft 19 mounted in suitable bearings 20 and driven in any suitable manner.- The several gears and pinions constitute speed-reducing trains of power-transmitting gears between the driving-shaft 19 and the shafts 13 of certain of the lower rolls. Each of the shafts 13, equipped with a drivinggear 14, is provided at the opposite side of the machine (see Fig. 2) with a gear 21, meshing with a smaller gear 22,carr1ed by the adjacent end of the upper shaft 10.` Thus the rolls of each pair, whose lower member is geared to the driving-shaft, are eared together, so that' both `are positive y driven,

IDO

In the illustrated machine, which is designed more paticularly for the manufacture of small tubes `of comparatively light material, each alternate pair of rolls is positively driven.

In Figs. 9 to 15, inclusive, the several pairs of skelp-bending or tube-forming rolls are shown in section. The skelp or blank is first presented between the upper and lower rolls 3a and 3b of the first pair 3. 'The roll 3b is provided with a peripheral groove or channel 3c, having a curved bottom 3d and straight diverginfr sides 3e. The cooperating roll 3a is provided with a peripheral pro'ection 3f substantially corresponding with t e groove or channel 3c and extended therein, as shown in Fig. 9. As the skelp is passed between the rolls 3a and 3b it is bent into trough shape and in this form is advanced to the second pair of rolls 4, the up er and lower rolls 4 and 4b being provide respectively, with a peripheral pro'ection 40 and a peripheral groove 4d, similar to the corresponding feai tures of the rolls 3a and 3 b, except that the radius of the curved bottom of the groove 4d substantially corresponds with the radius of the finished tube and thatthe conver ence of the side walls, of the groove is somew at less than in the case of the roll 3b. As the skelp passes through this second set of rolls the straight sides thereof are urged toward each other preparatory to the bendin of said sides into parallel relation as the ske p 4passes between the rolls 5a and 5b of the third pair or set 5. (See Fig. 11.) The rolls 6*L and 6b of the next set 6, unlike the rolls of the preceding sets, are both formed with peripheral depressions or rooves, the groove 6c in the lower roll 6b I) section and the roove 6d in the roll 6a having divergent side Walls 6e and an angular bottom wall Gf; As the skelp asses through these rolls its semicylindrica base is supported in the groove of the roll 6b, while its parallel sides are urged into convergent relation by the side walls of the groove in the roll athe edge faces of the skelp bearing against the\a'ngular bottom wall of said groove to prevent distortion of the metal during the bending operation.

The lower roll 7b of the next set is identical with the roll 6b and the upper roll 7 a corresponds with the roll 6, except ,that the side walls of its peripheral groove or channel are transversely curved and have a somewhat greater convergence, the angle of the bottomV wall of the groove being correspondingly changed to form a seat for the edge faces of the skelp. As the skelp passes between these rolls 7 a and 7b its side edges disposed above the semicylindrical'lower portion or base of the skelp are urged closer together and given an inward curvature. This ap roach of the skelp sides is augmented and't e curvature i increased until a nearly cylindrical or tubular: form is assumed by the passage of the 'the upper roll 8a.

eing semicylmdrical in cross-- skelp between the rolls 88L and 8b of the next set, which correspond to the rolls 7a and 7b,

except for the greater curvature and convergence of the side walls of the groove in The skelp now passes to the final set 9 of the skelp-bending rolls, which complete the formation of a perfect tube or cylinder of normal dimensions-that is to say, of-the size of the finished tube-the peripheral channels of these rolls 9'l and 9 being semicircular in cross-section to form a true cylindrical opening or pass.

The mechanism thus far described constitutes one embodiment of skelp -bending means which is capable of bendin the skelp into tubular form without materia lon itudinal bending or distortion; but it is to e understood that a greater or less number of sets of rolls may be employed, accordingly as it is desired to bend the skelp more or less-gradually in the formation of the initial tube. In fact, in its broader 'aspect the vinvention contemplates the bending of the skelp into tubular or true cylindrical form preparatory to the performance of certain other operations regardless of the particular character of the skelp-bending mechanism em loyed. It is therefore within the purview o the invention to utilize the several illustrated sets of rolls, a greater or less number thereof, or an entirely different character of mechanism for impartin tubular form to the skelp.

en the tube issues from between the last set Q'of skelp-bending rolls, it is in true cylindrical form, as stated, and it is at this oint that ordinary methods of producing a utt-joint tube terminate. I find, however, that at this stage the edges ofthe skelp, although brought intoabutting relation by the rolls 9a and 9b, have a tendency to spring apart as soon as the metal'passes beyond the rolls and is relieved of the pressure exerted thereby. This tendency results in the opening of the seam or joint and is obviously due to the resiliency of the metal, which is frequently manifested by the opening of the seam even when the edges of the tube are slightly overlapped. It is therefore aimed to overcome 4this expansive tendency of the tube, so as to insure a close joint of either a butt 'or lap type.

In advance of the bending set 9 a supplemental frame 23 is mounted on the base-plate 1. Within this frame, at its rear end, are

mounted a pair of guide-rolls 24 and 25, Vrooved to form a pass of true cylindrical orm forthe reception of the tube as it extends beyond the rolls 9a and 9b. The rolls 24 and 25 serve to guide the tube to what 'may be arbitrarily termed the "edge-flexing mechanism. The villustrated embodiment of this mechanism includes two comparatively large lower rolls 26 and 27, mounted in the supplemental frame 23 in closely- 4adjacent relation, as shown in Fig. 5, and

` vide each l each having a semicircular peri heral channel corres onding in radiuswit that of the tube, as s own in Fig. 16.

Disposed in a plane Yabove the rolls 26' and 27 are three somewhat smaller ed e-'flexing rolls 28, 29, and 30, the rolls 28 an 30 bein located directly above the rolls 26 and 27 an the roll 29 being disposed between the rolls 28 and 30 and directly above the interval between the two lower rolls 26 and 27. The two lower rolls afford an extended support for the tube and the three upper rolls serve to flex or depress, one edge of the tube to present it immediately below the other edge thereof,

each of these upper rolls being provided with a peripheral depresslng or flexing fl ge 31 approximately alf as wide as the tube and having a curved peripheral surfacel 32,which engages and flexes an upper quarter-section ofthe tube for the purpose of presenting the edges of the skelp in different horizontal planes, as stated. 4'llhe reason'for the employment of a series of these edge-flexing rolls instead of a single roll is that this repeated or continuedflexing of the metal is re-l quired in order to overcome the reactive tendency of the. metal, which would otherwise cause the depressed edge of the tube to spring back toits original position opposite t e other edge ofthe skelp.

The next operation comprehends the contraction of the tube to lap the edges thereof by the external application of radial pressure at a number of points. This contraction of the tube is preferably effected by'urging the same through a comparatively restricted pass defined by the edges of four contracting-rolls 33 34, 35, and 36, having their shafts disposed in rectan ular arrangement and mounted in bearing-b ocks 37, carried on the front end' late 38 of the su plemental frame 23. .Whi e the mounting o these rolls is subject to variation, the blocks37 are preferably provided'with longitudinal tongues 39, slidably received by radial guides 40 formed in the late 38. For the purpose of effecting the ongitudinal adjustment of the blocks and the conse uent adjustment of the rolls, I prolock at the outer end thereof with a lu 41, through which is passed an adjustingolt 42, the inner end of which is screwed into the plate 38, as shown in Fig. 5. When the block has been adjusted, it is rigidly-retained by retaining-screws 43, screwed into the plate 38 and passed through slotted ears 44; extending from the opposite sides ofthe block, as shown in Fig. 6.

' As the tube advances beyond the edge\flex ing or depressing rolls 28, 29, and 30 1t enters vthe constricted pass formed by the four contracting-rolls, each of which engages a quarter section of' the tube. Asv the tube ad- ,varices through this constricted pass it is uniformly contracted by the application of radial pressure at a plurality of points, and the a tendenc `which ten ency is resisted by the contact of v l skelp is thus coiled upon itself sufficiently tol cause the overlapping of its longitudinal edges. Thus when the skelp has assed beyond the contracting-rollsit is in t e form of a tube closed at one side by a lap jointvor seam which may or may not be subse uently welded in any approved manner. T e formation of this lap-joint tube is incidental to the preparation of the skelp inthe manufacture ofa butt-joint tube by my apparatus, and since it may be desired to construct lapjoint tubes attention is directed to the fact that the mechanism thus far described constitutes a complete embodiment of the invention in one aspect-that is to say, when viewed as an apparatus for 'the production-of lap-joint tubing. Primarily, however, the invention is directed to the production of a buttjoint tube in which the edges instead of having a normal tendency to spring apart will have a normal tendency toward each other-in fact, to move beyond each other,

the abutting edges of the skelp.` Upto this point the operationl consists in first bending the skelp into true cylindrical form, next depressing one edge, and finally uniformly contracting the skelp to impart a spiral form thereto. `It will now be apparent that if the `skelp is expanded in a manner to cause the reassumption of its cylindrical form the inherent stress or resiliency of the metal, caused by the previous contraction of the tube to less than normal dimensions, will urge the edges of the skelp toward each other with considerable force and will hold said edges in close relation after they have been presented in a common plane by the expansion of the lapjoint tube to true cylindrical form. This 'expansion of the lap-joint tube is effected by the application of internal pressure produced bythe movement of the tube over a man- :drel 45. This mandrel is located beyond the contracting-rolls 33 to 36 and is detachably securedaatvthe front end of a mandrel-rod 46, which extends back throu h the passes defined bv the contracting Jolis, the edgefiexing rolls, the uide-rolls, and the last two I.sets 8 and 9 of s elp -bending rolls, beyond which latter it is terminally supported b a gsleeve 47, connected to a mandrel-rod brac ret I48 by a thin intermediate web 49 suh'iciently :narrow for rece tion between the edges of Vthat portion of the skelp located between the jbending sets 7 and 8. The rod-bracket 48 is rigidl secured` to the frame structure of the -machine at a suitable point, and longitudinal movement of the rod 46 within the sleeve 47 is prevented by a key 50, as shown.- It may be stated in passing that the particular location of the support for the mandrel-rod is not essential. On the contrary, while the bracket 48 is `shown located between the fifth and sixth sets of bending-rollsthe rod might be extended still nearer the front end of tlie ma- IOO reol

sis of the tube by the contracting-rolls.v This chine, in which case the location of its support Will-be correspondingly changed.

The diameter of the mandrel-rod 46 is such v points upon which the ed e flexing and contracting rolls ofperate. T e diameter of the rear end 458L o the mandrel 45 corresponds with that of the mandrel-rod 46; but fromthis end the dimensions of the mandrel adually increase until they correspond wit the internal diameter of a completed butt-joint tube, the remaining portion of the mandrel being of true cylindical form, as shown. In other words, the mandrel comprises a plain cylindrical portion 45b of a diameter'corresponding to the internal diameter of a finished butt-joint tube and a tapered end 450, which connects the lain cylindrical portion 45b with the mandre -rod. The tapered end 45c constitutes an expander which causes the lapped or contracted tube to be gradually expanded as it moves rearwardly, so that when said tube passes onto the cylindrical portion 45b of the mandrel it Will have been restored to its original cylindrical form and with.'its

' edges abutted. The form of that'portion of the tube passing over the cylindrical portion of the mandrel will be identical with that portion of the tube which is passing between the skelp-bending rolls 9a and 9b. While the form of the tube at these points is the same,

tendency to contract.

however, the stress of the metal is reversed. In other words, when the tube issues from between the rolls 9a and 9b its tendency is to expand, and thus separate the abutting edges, while the tendency .of that portion of the tube located on the mandrel is to contract, and thus urge its edges into close contact. At this stage-that is to say, when the tube has again assumed'its normal dimensions by expansion upon the mandrel-#the tendency of the tube to contract is not only sufficient to retain the edges of the skelp in close contact, but is suflicient to cause the previously deflected or depressed edge ofthe skelp to move inward and under the opposed edge in case.

the tube receives yrough handling-such, for instance, as will exert an inward pressure on such edge-and thus augment its natural To avoid this possibility, the next operation involves theoutward flexing of that edge of the skelp which was inwardly iexed prior to the contraction outward iexing of the skelp edge is effected by a die 51, carried by and projecting slightly beyond the surface of the mandrel, and this, while sufficient to counteract the tendency of the previously-flexed edge of the skelp to move inward toward the axis of the tube, is insuiiicient to counteract that tendency to contract which insures Athe closeengagement4 of the edges. AAs the tube, which is of true cylindrical form, advances from the cylindrical portion of the mandrel the edge thereof, which has heretofore been iiexed inwardly from its normal position, rides over the die 51 and is :flexed outwardly from its normal 7 position. 51 the outwardly-Hexe its normal position; butsince the outward iiexing will have counteracted its excessive tendency to move inward the product of the method will be a butt-joint tube having its edges urged into close contact by the inherent resiliency of the metal and capable of suse taining rough handling rwithout danger of As the tube (passes beyondthe die opening the seam or joint or of causing the 8 lap ing of the edges.

should be understood that in its broader l aspects the invention comprehends the employment not only of the various mechanisms described but of equivalent mechanisms 8 for performing 'the recited functions. In Fig. 8, for instance, is disclosed a modified form of die 51a, which instead of being rotary is in the form-of a swinging arm adjustable radially with respect to the mandrel for the purg ose of regulating the de ree of outward flex- 1on Vof the skelp edge. herefore, While the apparatus shown is thought at this time to be preferable, I desire to reserve the right to ef fect such modifications orj variations thereof g as may come fairly within the scope of theprotection prayed.

While the foregoing is a complete description of the apparatus s far as the mereformation of a butt-jointtube is concerned, it I happens that even when the bending of the skelp is effected gradually, as in the illustrated form of ap aratus, the completed tube will not be absolutely straight as it passes from the mandrel. connection with the mechanism described, a novel form of tube-straightenin mechanism comprising a set of horizontal ro ls 52, 53, and 54 and a second set of vertical straighteningrolls 55 ,.56, and 57, the rst roll 55 of the vertical seibeing located in a lane intermediate of the second and third rol s 53and 54 of the Y horizontal set, asshown in Fig. 3. These rolls are adjustably mounted, as shown, and effectually straighten the tube prior to its de-'.,1 livery from the machine.

1. In a tube-making machine, the combination with skelp bending mechanism, of edge-flexing mechanism arranged to exert an inward radial pressure upon the tube .adjbacent to one ed e aftersaid tube is formed 2. In a tube-malcinnmachine, the combination with skelp-ben gmechanism adapt- -ed for the formation of a tube, of a series of edge-flexing rolls disposed'to operate upon edge springs back to I therefore employ, in i the tube at successive points after said tube has been formed by the skelp-bending mechedge-flexing rolls arranged to flex one edge of and tube-contracting anism, and tube-contracting mechanism.

3: In a tube-maln'n machine, the combination with skelp-ben 'ng mechanism adapted for the formation of a tube, of a series of the tubeinwardly to present the edges o the skelp out of coincident relation, and ,tubecontracting rolls disposed in quartering relation about a constricted pass within which the tube is contracted to convolute form. v

4c. .The combination with a series of skelpbending rolls adapted to bend the skel into cylindrical form, of ed e flexing rol s disposed beyond the skelpending rolls and arranged to Hex one edge ofthe tube inwardly, rolls located beyond the edgeiiexing rolls and forming a constricted pass within which the tube is contracted to lap the edges thereof 5: In a tube-making machine, the combi natlon withv mechanism for bending the skel to the form-of a tube having its edges lappe of means for expanding the tube to `present.

i its edge faces out of lapping relation.

tion.

6: In a tube-making machine,v the combi natlon with mechanism for bending the skelp 1nto the form of a tube having its edges lapped, of a mandrel arranged to expand the tube to present its edges out of lapping rela# 7l In a tube-making machine, the combination with mechanism for bending the skelp into the form'of a tube having lapped edges, of means for ex anding the tube to present the edges thereo out of lapping relation, and meansv for outwardly flexing that edge of the tube having the greatest inward'stress, substantially as described.

8. In a tube-makingfma'chine, the combination with'mechanism for bending the skelp into the form of a tube having its edges lapped, of a mandrel disposed to expand the tu e to present its edges out of lappingrelation, and an edge-iiexing die carried by the mandrel and arranged to iiex one edge of the tube outwardly beyond the normal dimensions of the tube.

9: In a tube-making machine, the combination with mechanismfor bending theskelpinto Vtubular form, meansfor iiexing one edge only of the tube inwardly, means for contracting the tube, and tube-expanding means. 10. The combination with mechanism for bending the skelp into tubular form, of edgeexing mechanism arranged to flex one e of the tube inwardly, tube-,contracting mec anism arranged to contract the tube to lap the edges thereof, means for ex anding the tube to normal dimensions, and) means for .iiexing outwardly beyond the normal dimensions of the tube that edge of the skelp which was previously flexed inw dly.

11. In a tube-makinglmachine, the combination with an edge-flexing device, of tubecontracting mechanism located beyond the same, tube-expanding mechanism located be-- yond the contracting' mechanism, and a second edge-flexing device located beyond the tube expanding mechanism, the iirst ed eiexing device serving to Hex an edge of t e tube in one directionprior to the contraction and 'expansion of the tube, and the other edge-fiexing device serving to flex the edge of the tube in the ,opposite direction after the tube has been contracted and expanded.

12. 'The combination with a series of skelpbending rolls arranged to bend the skelp into cylindrical form,`of an edge-iiexing roll, tubecontracting rolls, a tube-expanding mandrel, and an edge-flexing die disposed inthe order stated to act successively upon the same portion of the tube.

13. In a tube-makin machine, the combi nation with a series of s {clp-bending rolls arranged to bend the skelp into cylindrical form, a series of edge-flexin rolls disposed beyond the skelp-bending rol s to flex one ed e ofthe tube inwardly, tube-contracting ro s disposed in quartering relation about a constricted pass within which the tube is contracted to convolute form, a mandrel dis-l posed to expand the contracted tube to its original cylindrical form, and a die disposed to Hex outwardly beyond4 its normal plane that edge of the tube which was previously flexed inwardly from its 'normal plane.

14. In a tube-making machine, the comblnation with means for bendingv the skel into the form of a complete butt-joint tu e, of means for transforming said butt-joint tube into a lap-joint tube, said last-named means including a series of contracting-rolls arranged to form a constricted pass the wall of which is of volute form.

15. In a tube-making machine, the combination with skelp bending mechanism, of edge-ilexing mechanism arranged to iiex one edge of the tube inwardly after said tube 1s formed by the skelp-bendmg mechanism, and tube-contracting means for contracting 'the tube to cause the edges thereof to overlap.

16. In a tube-making machine, the combination with skelp bending mechanism, of edge-flexing mechanism arranged to exert an inward radial pressure u on the tube adjacent to one edge after sai tube is formed by of the Aedges thereof. l 17. In a tube-making machine, the comblnation With skelp-bend1ng mechanism ada ted for the formation of a tube, of means or' flexin one edge of the tube inwardly to resent the edges of the skelp out of coinci ent relation, and tube-contracting rolls forming a constricted pass within which the tube is contracted to convolute form.

18. In a tube-making machine, the combilthe skelp-bendlng mechanism, and means .for v contracting the tube to cause the overlapping form, of an ed e-iiexing ro disposed beyond the skelp-ben ing rolls and arranged to lex one edge of the tube inwardly to present the edges of the skelp out of coincident relation, and means located beyond the edge-flexing roll for contracting the tube to cause the edges thereof to overlap.

20. In a tube-making machine, the combination with mechanism for bending the skelp into the form of a tube having lapped edges, of means for transforming the tube t us formed into a butt-joint tube, said transforming means including means for outwardly iexing that edge of the tube having the greatest inward stress.

21. In a tube-making machine, the combination with skelp-bendln means arranged to bend the skelp into cylin rical form, of edgelexing means, tube-contracting means, tubeexpandin means, and a second edge-flexing means, al disposed in the order stated to act scpessively upon the same vportion of the s e p.

22. In a tube-making machine, the combination with mechanism for bending the skelp to form a butt-joint tube, of mechanism for contracting said butt-joint tube to transform the same into a lap-joint tube, and mechan- 1sm for expanding the transformed tube to again roduce a tube of the butt-joint t e.

23. n a tube-making machine, the com ination with skelp-bending mechanism, of an edge-ilexing roll arranged to ex one edge of the tube inwardly after said tube is formed by the'slselp-bending mechanism, and tubecontracting means for contracting the tube to cause the edges thereof to overlap. 24. In a tube-making machine, the combination with mechanism for bending the skelp into the form of a tube having its ed es lapped, of a mandrel disposed to expand t e tube to present its edges out of lappingl relation, and

edge-exing means arranged to iiex one edge of the tube outwardly beyond the normal dimensions ofthe tube.

25. In a tube-making'machine, the combination with .mechanism for bending the skel to the form of a tube having its edges lapped), of mechanism for expanding the tube to urge the inner ed e outwardly beyond a .point opposlte the ot er edge, whereby when the outward pressure is relieved, the outwardly-expanded edge will spring back to complete the formation of a butt-joint tube.

In testimony that I claim the foregoing as my own I have hereto aiixed my signature in the presence of two witnesses.

GEORGE B. MELLINGER.

Witnesses:

F. L. BROWN, ELTA F. BURNS.

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