Segmented back-up bar for butt welding large tubular structures such as rocket booster bodies or tank

Franklin, W. J.

Martin, N. C.

English

NASA Technical Reports Server

W. J. FRANKLIN ETAL 3,229,884 
SEGMENTED BACK-UP BAR 
F i l e d  Jan. 30, 1964 5 Sheets-Sheet 1 
WILLIAM J. FRANKLIN, 
NEIL C .  MARTIN, 
INVENTORS 
A T TO R NE YS 
https://ntrs.nasa.gov/search.jsp?R=19700030608 2020-03-17T02:09:58+00:00Z
Jan. 18, 1966 
Filed Jan. 30, 1964 
W. J. FRANKLIN ETAL 
SEGMENTED BACK-UP BAR 
5 Sheets-Sheet 2 
3 
7 
6 
I 
109 
19 J 
FIG. 2 
W I L L I A M  J. FRANKLIN,  
N E I L  C. M A R T I N ,  
INVENTORS 
Jan. 18, 1966 W. J. FRANKLIN ETAL 
SEGMENTED BACK-UP BAR 
Filed Jan. 30, 1964 
,229, 
5 Sheets-Sheet 3 
/’ I 
WILLIAM J FRANKLIN, 
N E I L  C. MARTIN, 
INVENTORS 
A JTORNEYS 
Jan. 18, 1966 W. J. FRANKLIN ETA 
SEGMENTED BACK-UP BAR 
Filed Jan. 30, 1964 
3 , ~ 2 ~ , g g ~  
5 Sheets-Sheet & 
WILLIAM J. FRANKLIN, 
N E I L  C. MARTIN, 
INVENTORS 
ATTORNEYS 
Jan. 18, 1966 
Filed Jan. 30, 1964 
W. J. FRANKLIN ETAL 
SEGMENTED BACK-UP BAR 
4 
5 Sheets-Sheet 5 
41 
11111 I I I I 
FIG.9  
WILLIAM J. FRANKLIN, 
N E I L  C. MARTIN, 
ZNVEN TORS 
1 
3,229,884 
William J. Franklin and Neil C. Martin, Huntsville, Ala., 
assignors to the United States of America as represented 
by the Administrator of the National Aeronautics and 
Space Administration 
Filed Jan. 30,1964, Ser. No. 341,467 
5 Claims. (CI. 228-50) 
(Granted under Title 35, U.S. Code (1952), sec. 266) 
The invention described herein n a y  be manufactured 
and used by or for the Government af the United States 
of America without the payment of any royalties there- 
on or therefor. 
This invention relates to improvements in backing ele- 
ments for the use in welding operations and more particu- 
lar to a back-up bar for use in welding cylindrical tubular 
structures. 
It is a common practice in butt welding edges of plates 
to apply a back-up bar or strip on the side opposite the 
welding operations to prevent the molten weld metal 
from running out of the joint or seam. The back-up bar 
maintains uniform contact with the plates at opposite 
sides of the seam to retain all the moiten metal in the 
seam during the welding operation and to aid in the align- 
ment of the plates. 
In assembling the large cylindrical tubular body or tank 
sections of large rocket boosters, each sections has here- 
tofore been welded to its adjacent section by utilizing a 
substantially continuous back-up bar which was designed 
and built for the specific diameter of the joint seam being 
welded. These backup bars were normally supported 
from the floor by a large center “spider” structure which 
extended within the tubular sections which were located 
endwise to the floor. The “spider” structure urged the 
back-up bar tightly against the surfaces of the tubular 
sections adjacent the contiguous end edges which were 
to be welded. 
This arrangement, however, becomes excessively ex- 
pensive and cumbersome for cylindrical tubular body sec- 
tions having large diameters. Even a slight change in 
the size of the body sections requires extensive modiflca- 
tion of the back-up bar and its supporting “spider” struc- 
ture. Also, the back-up bar and its supporting structure 
requires a considerable amount of valuable floor space 
whether it is in use or not. 
Accordingly, it is an object of the present invention to 
provide a back-up bar which is substantially self-support- 
ing, thereby, eliminating the need for a large supporting 
structure. 
Another object is to provide a back-up bar which may 
easily be assembled from segments and then later disas- 
sembled for storage. 
Yet another object is to provide a back-up bar with a 
contact surface plate which is longitudinally extending 
flexible and also yieldable to maintain the bar tightly 
against the plates at opposite sides of the seam. 
Other objects, uses, and advantages of the present in- 
vention will become apparent as the description proceeds. 
The invention consists of a back-up bar composed of 
similar short arcuate segments. Each segment having a 
rigid channel member which receives an elastomeric rib- 
bon member which has a plurality of contact surface 
plates dovetailed therein. Beneath the elastomeric ma- 
terial is an inflatable bladder which is adapted to inflate 
and push the elastomeric ribbon member so its contact 
surface plates are pressed against the tubular body sec- 
tions at opposite side of the seam. 
The arcuate back-up bar segments are assembled di- 
rectly on one of the tubular body sections by utilizing 
simple support devices which temporarily attach them- 
SEGMENTED BACK-UP BAR 
selves directly on a body surface adjacent the edge to be 
seam welded. When the arcuate back-up bar segments 
are assembled to form a complete ring within the tubular 
section, the bladders of each segment are inflated to cause 
5 the contact surface plates to press against the tubular body 
sections on each side of the seam so that the back-up bar 
ring frictionally grips the body sections and becomes self- 
supporting. The simple support devices are under no load 
following inflation of the bladders. Thus, it can be seen 
10 that the cumbersome separate supporting structure used 
heretofore has been eliminated. While it is apparent that 
the back-up bar of the present invention is particularly 
valuable for tubular sections having a diameter of twenty 
feet or more, it may also be readily used for much smaller 
This will be more readily understood by the fiollowing 
detailed description when taken together with the ac- 
companying drawings in which: 
FIGURE 1 is a perspective view of two tubular sec- 
20 tions with a back-up bar of the present invention along 
FIGURE 2 is a cross-section view taken along line 
FIGURE 3 is a longitudinal cross-section view of one 
25 segment of the back-up bar shown in FIGURE I; 
FIGURE 4 is a perspective end view of one end of a 
segment af the back-up bar shown in FIGURE 1; 
FIGURE 5 is a perspective view illustrating the first 
step taken before assembling the back-up bar shown in 
FIGURE 6 is an enlarged perspective view of a vacuum 
holding device being positioned in FIGURE 5; 
FIGURE 7 is a perspective view illustrating the assem- 
bly of the back-up bar shown in FIGURE 1, the top tubu- 
FIGURE 8 is an enlarged disassembled perspective 
view taken along line 8-8 of FIGURE 7 showing a line 
joint between segments of the back-up bar. 
FIGURE 9 is a perspective view illustrating the plac- 
40 ing of the final segment of the back-up bar of FIGURE 1, 
the top tubular section and air hoses being removed for 
clarity; 
FIGURE 10 is an enlarged perspective view of the final 
back-up bar segment being placed in FIGURE 9. 
Referring now to FIGURE 1 which shows two large 
cylindrical tubular sections 11 and 13 with a circular 
ring back-up bar 15 of the present invention along the 
joint 16 to be welded. 
The back-up bar 15 is composed essentially of similar 
50 line segments 17. Each segment 17 as illustrated in FIG- 
URES 2 and 3 has a rigid arcuate I-shaped frame 19. In 
the outer channel 21 of the I-shaped frame 19 is fitted a 
heat resistent, resilient, flexible, ribbon member 23 which 
has a plurality of longitudinally contiguous contact sur- 
Beneath the ribbon 
mmeber 23 and bonded thereto is an inflatable bladder 27 
which is adapted to inflate and push the ribbon member 
23 so its surface plates 25 are pressed against the inner 
surface of the tubular body sections 11 and 13 at op- 
6o posite sides of the joint 16 to be welded. The inflatable 
bladder 27 is bonded to the web 29 of the rigid frame 
19 and has a single air inlet tube 31 which extends 
through a hole 33 in the frame web 29 and is securely held 
therein by a threaded nut 35. 
Each contact surface plate 25 is elongated and trans- 
versely aligned to the ribbon member 23 so it may easily 
conform to the longitudinal irregularities and warpage 
of the tubular sections 11 and 13 and also easily be 
adapted to rigid frame members of different diameters. 
The width of the plates 25 is not critical and depends 
on the expected longitudinal variance needed. 
15 tubular sections. 
the joint to be welded: 
2-2 of FIGURE 1; 
30 FIGURE 1; 
35 lar section being removed for clarity; 
45 
’’ face plates 25 dovetailed therein. 
65 
3,229,884 
3 
The contact surface plates 25 may have a conven- jacent the final back-up segment 77 are also modified 
tional groove 37 or mold which will receive the molten as shown by FIGURE 10. Each end has a stop plate 
metal from the seam joint 16 during the welding opera- 81 upon its upper surface so that when the final seg- 
tions to form a bead along the underside of the weld. ment 77 is dropped between the adjacent segments 17, 
Because of the high heat involved at the joint 16, it 5 the final segment 77 may be pushed outwardly until its 
is preferred if the surface plates 25 are made of stain- bar 79 contacts the notched surface 83 of the stop plate 
less steel and the ribbon member 23 be made of silicone 81 which is so located that the contact surface plates 
rubber. The inflatable bladder 27 may be made of (not shown) at the final back-up bar segment 77 will 
natural rubber. be in perfect alignment with the contact surface plates 
At one end of each normal or line back-up bar seg- 10 25 of the adjacent line segments 17. 
ment 17 is a splice plate 39, shown best in FIGURE 8, The ends of the back-up segments 17 adjacent the 
which is secured to the inside channel 41 of the rigid final back-up bar segment 77 are further modified as 
frame 17 by two bolts 43 so approximately half its follows. One end of the adjacent normal segments 17 
length extends outwardly from the segment end to be has a L-shaped block 85 secured to the inside recess 
received within the inside channel of the frame of the 15 channel 41 with a longitudinal threaded bore 87 extend- 
adjacent back-up bar segment 17. The normal back- ing through its upstanding leg 89, and the end of the other 
up bar segment 17 has at least one bore 45 extending adjacent normal segment 17 has a Gshaped block 91 
through the inside flanges of the I-shaped frzme 19 secured within its inside recess channel 41 with a slot 
adjacent the end 47 opposite the splice plate 39. The 93 extending from the end surface of its upstanding leg 
bore 45 aligns with a bore 49 in the splice plate 39 of 20 95. A known turning screw having a fixed screw 99 
the adjacent back-up bar segment 17 so a dowel 51 may threaded into the bore 87 and a sleeve 97 which is 
be dropped therein to securely lock the adjacent segments notched so as to rotatably fit within the slot 93 is used 
17 together. to tighten the adjacent back-up bar segments 17 against 
The back-up bar segments 17 are assembled along the the final back-up bar segment 77. The sleeve 97 is pro- 
joint 16 of the two tubular structures 11 and 13 to be 25 vided with a wrench gripping surface 101 to aid in the 
welded together by a workman 53 supported on a mova- rotation of the turning screw. 
ble platform 55, as illustrated in FIGURES 5, 7 and 9, With the placing of the final back-up segment 77, 
who first places a known type vacuum chuck 57 along air pressure is applied through a suitable pump (not 
the inner surface of the first tubular structure 11 ad- shown) by a lead hose 105 (see FIGURE 1 to 7) to a 
jacent the end edge 60 to be welded. 30 manifold hose 107 which in turn distributes the air by 
As shown best in FIGURE 6, the vacuum chuck 57 individual hoses 109 to the inflatable bladders 27 of each 
has a gauge 59 pivotally fastened to its upper portion back-up bar segment. The expansion of the bladders 
by which the workman 53 may easily position the 27 forces the contact surface plates 25 against the inner 
chuck 57 at its proper distance from the joint to be surfaces of the tubular sections 11 and 13 at opposite 
welded. As illustrated in FIGURE 5, the workman 53 35 sides of the joint 16 causing the two surfaces to align 
places the cantilevered portion 61 of the gauge 57 against themselves and causing a frictional griping force such that 
the end edge 60 of the tubular section 11 and thereby the back-up bar ring 15 becomes self-supporting. 
aligns the vacuum chuck 57 in its proper position for Following the welding operation, the bladders 25 may 
receiving the back-up bar segments 17 upon its support- 4o be deflated and the back-up bar 15 disassembled in a 
ing surface 63. Following the alignment of the chuck manner reversed to its assembly. 
57, the gauge 59 will be pivoted backwards so as not Thus, it can be seen that a novel back-up bar for 
to interfer with the supporting surface 63 of the chuck welding has been disclosed which aids in the alignment 
57. of the edges of the tubular sections to be joined and 
The exhaust port 65 of the vacuum cup 67 of each which is substantially self-supporting when in use. Also, 
chuck 57 is joined to a circular manifold hose 69 by 45 the back-up may easily be broken into segments for 
a separate hose 71. The manifold hose 69 is in turn storage in a minimum of space and later be assembled 
connected to a vacuum pump (not shown) by a single again. 
hose 73. The resilient and flexible ribbon member and its con- 
Following the placing of the vacuum chuck 57, the tact surface plates are longitudinally extending flexible 
workman 53 places each of the back-up bar segments 50 and also yieldable to conform readily to the warpage of 
17 on the chuck's supporting surface 63 in the manner the structures along the seam during the welding opera- 
illustrated by FIGURE 7, the upstanding projection 75 tions SO as to retain all molten metal in the seam during 
(shown in FIGURE 6) of each vacuum chuck 57 serves the welding operation. 
as a stop to prevent the back-up bar 15 from being Also, the bladder and resilient ribbon member may 
accidentally knocked-off the supporting surfaces 63. Ad- 55 easily be removed and replaced if damaged or adapted 
jacent back-up bar segments 17 are joined by the splice to another rigid frame member of another diameter with 
plate 39 shown in FIGURE 8 and previously described. aminimumof cost. 
The final arcuate back-up bar segment to be placed Obviously many modifications and variations of the 
by the workman 53 will usually be of a special length present invention are possible in light of the above teach- 
frame with the splice plate 39 of the normal segment '' ings. It is therefore to be understood that within the 
17 removed. A typical final back-up bar segment 77, scope of the appended claims the invention may be prac- 
illustrated in FIGURES 9 and 10, consists of the stand- ticed other than as specifically described. 
ard I-shaped frame 78 having the inflatable bladder and What is claimed is: 
the flexible, resilient ribbon member with its contact 1. A back-up bar for use internally at abutting ends 
surface plates within the outer channel recess. Although " of tubular members while said members are being welded 
the outer channel recess of the frame 78 is not shown together and adapted to be easily removed after the weld- 
in FIGURES 9 and 10, a cross section view of the frame ing operation, comprising: 
78 would be substantially the same as the cross section (a) a plurality of arcuate short back-up bar segments, 
view shown in FIGURE 2 of the line or normal line 
segment 17. (b) each said back-up segment comprising; 
An elongated alignment bar 79, however, is secured 
upon the upper surface of the final back-up bar segment 
77 and extends beyond each end of the segment. The 
contiguous ends of the back-up bar segments 17 ad- 75, 
joined end-to-end to form a continuous ring; 
(1) an elongated rigid frame member having an 
(2) an inflatable bladder at the bottom of the 
outer channel recess; 
recess of said rigid frame member; 
3,229,884 
(3) a resilient, flexible ribbon member supported directly to said ribbon member whereby the contact 
upon said infiatable bladder, and surface for the back-up bar will be longitudinally 
(4) a plurality of elongated contiguous contact extending flexible and also yieldable. 
surface plates forming the back-up contact sur- 4. A backing element for use in welding operations, 
face for said segment; comprising: 
(5) each said contact surface plate being trans- 5 (a) rigid framemember; 
versely aligned to said ribbon member and se- (b) an elongated heat resistant elastomeric ribbon 
cured thereto whereby the contact surface for member; 
said segment will be longitudinally extending (c) an extensible means securing said ribbon member 
flexible and also yieldable to maintain the back- to the surface of said frame member; 
up bar tightly against the internal surface of 10 (d) a plurality of elongated contiguously arranged 
said tubular members at opposite sides of their plates having a lower surface and an upper surface, 
abutting edges. the upper surfaces of all said plates forming a back- 
2. A self-supporting back-up bar for use in butt weld- up contact surface; 
ing tubular structures, comprising: (e) each said plate being transversely aligned to said 
(a) a plurality of short arcuate back-up bar segments 15 ribbon member and having its lower surface secured 
joined end-to-end to form a ring; directly to the outer surface of said ribbon member 
(b) each said segment having: whereby said contact surface will be longitudinally 
(1) a rigid frame member; extending flexible and also yieldable; and 
(2) an infiatable bladder joined to said rigid frame (f) said extensible means adapted to uniformly push 
member; the ribbon means so its contact surface plates will 
(3) an elastomeric ribbon member joined to said press against the surfaces the workpieces being weld- 
bladder; ed; 
(4) a plurality of contiguous plates secured to the 5. A backing element as defined by claim 4 wherein 
outer surface of said ribbon member so that a each said plate has a groove within its upper surface and 
contact surface is formed which is substantially 25 midway its length for receiving the molten metal from a 
flexible and yieldable. seam joint during the welding operations to form a bead 
3. A back-uu bar, comurisinn: along the underside of the weld. 
2o 
(a) an elongatedrigid-frame member having a channel 
recess; 
(b) an infiatable bladder at the bottom of the recess 30 
of said frame member. 
(c) a resilient, flexible ribbon member supported upon 
said inflatable bladder; 
(d) a plurality of elongated contiguously arranged 35 
plates having a lower surface and an upper surface, 
the upper surfaces of all said plates forming the con- 
- 
References Cited by the Examiner 
UNITED STATES PATENTS 
1,710,258 4/1929 Hume _ _ _ _ _ _ _ _ _ _ _ _ _  219-160 
1,902,051 3/1933 Wall _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _  228-50 
1,972,029 8/1934 Norquist _ _ _ _ _ _ _ _ _ _ _  219-160 
2,430,266 11/1947 Zimmerman _ _ _ _ _ _ _ _ _  228-50 
2,631,215 3/1953 Randall et al. _ _ _ _ _ _ _  219-158 
2,987,022 611961 Thielsch _ _ _ _ _ _ _ _ _ _ _ _  228-50 . .  
tact surface for the back-up bar member; 
(e) each said plate being transversely aligned to said WHITMORE A. \NILTzj Examiner* 
ribbon member and having its lower surface secured 40 M. L. FAIGUS, Assistant Examiner. 


Segmented back-up bar Patent

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