Apparatus for making butt-welded tubes

Apparatus for making butt-welded tube from a strip includes a pair of grooved weld rolls for aligning the longitudinal edges of the strip bent into a tubular shape. To insure that the inside seam of the tube is flush regardless of variations in thickness between strip edges, each roll is made in two sections. In a horizontal mill the seam is on top and each bottom roll section is fixed in horizontal position while the top roll section has limited axial movement. Resilient means bias the roll sections apart and against a top stop so that the top of one edge of the strip is higher than the other when the edges are of different thicknesses. If desired, the rolls may also be adjusted to insure that the outside seam of the tube is flush.

This invention relates to apparatus for making butt-welded tubes utilizing 
welding rolls and more particularly to making such tubes with a 
substantially smooth inner seam. It is common practice to make butt-welded 
tubes from rolled strip or skelp particularly steel and stainless steel 
strip. The strip is bent in a horizontal mill into tubular shape and then 
with its longitudinal edges close together the strip is passed through 
grooved welding rolls mounted on vertical axes. Mills of this general type 
are shown in the patent to Morris U.S. Pat. No. 3,691,337 dated Sept. 12, 
1972, but the invention may be used with any tube welding rolls. 
One problem involved in this type of mill is to have proper alignment of 
the strip edges during welding. The problem is magnified by the fact that 
rolled strip is seldom of the same thickness across its entire width. Thus 
it is common for one edge of the strip to be thicker than the other edge. 
Prior to our invention it was common practice to remove the one-piece weld 
rolls from the weld roll block and add shims as required so that when the 
weld rolls were installed the tube edges aligned properly. This procedure 
is time consuming and requires a certain amount of guess work to determine 
the exact amount of shimming needed. When dimensional changes in skelp 
thickness occur the weld rolls have to be shimmed to align the skelp 
edges. Since the internal seam edges were offset, the aligned edges were 
aligned by gaging the OD of the tubing to be flush and allowing the edge 
dimension variance to be internal. As a result the internal scarfing tool 
tended to be unstable and not operate properly so that many tubes were 
rejected. In many cases, the formed tube shape leaving the last fin pass 
was not the shape of the weld rolls. 
It is therefore an object of our invention to provide welding rolls which 
will confine the bent strip in such a manner that either the internal seam 
or external seam edges are not offset. 
Another object is to provide such apparatus in which the rolls may be 
adjusted without removal.

Referring more particularly to the drawings reference numerals 2 and 4 
indicate a pair of weld rolls for receiving a bent strip or skelp S. Since 
the rolls are substantially the same only roll 2 will be described in 
detail. The roll 2 includes a vertical stationary shaft or spindle 6 
mounted in base 8. Surrounding the shaft 6 are antifriction bearings 10, 
each having an inner race 12 and outer race 14 with rollers 16 
therebetween. A sleeve 18 surrounding the bearings 10 has an inner flange 
20 extending into the space between bearings 10 and a lower flange 22 
extending outwardly. A ring 24 surrounding the shaft 6 at its upper end 
holds the bearings 10 in place. Oil seals 26 above and below bearings 10 
provide a sealed oil chamber 28 for the bearings. The roll proper is 
divided into lower section 30 and upper section 32. The lower section 30 
is fastened to sleeve 18 by means of cap screws 34 passing through flange 
22 into threaed holes 36 in role section 30 so that roll section is fixed 
with respect to sleeve 18. The upper section 32 is secured to sleeve 18 by 
a key 38. Keyway 40 in roll section 32 is longer than key 38 so that roll 
section 32 can move axially while rotating with shaft 6. A pressure nut 42 
is threaded on upper threaded portion 44 of sleeve 18 with its bottom 
abutting the top of roll section 32. In one roll the threads will be right 
hand and in the other, left hand. A pair of tapped holes 43 are provided 
through the wall of nut 42 for receiving set screws 43S. A tube 46 is 
received in a groove in nut 42 and is provided with scale markings 48 to 
indicate the vertical position of the nut. The scale markings 48 are 
preferably graduated in thousands of an inch and a scribe line 49 is made 
on roll section 32. Holes 50 are provided in nut 46 for ease of rotation 
by means of a tool. When assembled the scribe line 49 indicates the zero 
position when the wall thickness is uniform. A seal 52 is provided at the 
top of nut 46. A substantially semi-circular peripheral groove 54 is 
provided in the outer surface of the assembled roll sections with 
substantially equal portions in each section. Roll sections 30 and 32 have 
opposed peripheral grooves 56 and 58, respectively, in their inner surface 
for receiving compression springs 60. Upper and lower shoulders are 
provided by the grooves against which the springs bear. If desired, an 
upper ring 62 may be provided in groove 58 in lower retaining ring 64 
having upwardly extending pins 66, one for each spring may be provided in 
groove 56. In one particular embodiment 24 springs are provided in each 
roll. Tool receiving slots 68 are preferably made in sleeve 18. 
In operation, the pressure nut 42 is rotated to position it in the desired 
location. This is done by inserting a tool into one of the slots 68 to 
prevent sleeve 18 from turning and turning the nut 42 by a spanner wrench 
inserted into one of its holes 50. Set screws 43S are then screwed into 
holes 43 and against sleeve 18 to hold the nut 42 in the desired position. 
The upper roll section 32 is biased upwardly by springs 60 against the nut 
42 with back lash being negligent. Gap G between the roll sections in one 
particular embodiment may vary between 0 and 0.030 inches. With the strip 
edge thickness being equal each roll is adjusted to the same zero 
position. If edge El is thicker than edge E2 as shown in FIG. 1, the 
pressure nut of roll 4 is adjusted downwardly until the bottom of the 
edges are in alignment. It will be seen that if edge E2 is thicker than 
edge E1 the upper section of roll 2 will be lowered. 
It will be seen that the rolls may be adjusted in the opposite direction if 
it is desired to align the top of the edges rather than the bottom. 
Instead of both rolls being split, only one may be split and adjustable, 
but this limits the amount of control. 
While one embodiment has been shown and described, it will be readily 
apparent to those skilled in the art that various adaptations and 
modifications may be made within the scope of the invention.