Mechanism and method for removing twists in a tube forming machine

A mechanism and method for counteracting and removing the twist of a rolled metal strip being formed into a tube by a tube forming machine. The mechanism has a frame rotatably mounted to the tube forming machine between the forming rolls and the seam guide. A pair of edge rolls are attached to the frame and are engageable with the opposing longitudinal edges of the rolled metal strip. Backing rolls, also attached to the frame, inhibit the transverse displacement of the rolled metal strip by the engagement of the edge rolls with the longitudinal edges of the metal strip. An adjustment screw rotates the frame relative to the tube forming machine about a longitudinal axis to align the longitudinal edges of the rolled metal strip with a seam guide prior to welding the longitudinal edges to each other.

TECHNICAL FIELD 
The invention is related to the field of machines for making seam welded 
tubing from flat metal strips and, in particular, to a mechanism for 
counteracting and removing undesirable twists in the metal strip as it is 
being formed into a tubular shape to assist in alignment with and to 
prevent the edges of the metal strip from being deformed by the seam 
guide. 
BACKGROUND ART 
In the formation of seam welded tubing, a seam guide, as taught by Crawford 
in U.S. Pat. No. 2,936,357 and Hellman, Sr. in U.S. Pat. No. 4,905,885, is 
used to align the seam to be welded with the welder. However, due to 
imperfections in the metal strip, the formation of the seam by the 
preceding forming rolls will not be aligned with the seam guide. As a 
result, one edge or the other of the seam being formed may engage the edge 
of the seam guide with enough force to cause that edge to be galled or 
otherwise deformed and fail to maintain alignment under the welder. This 
deformation of an edge of the metal strip often results in defects in the 
welded seam and the misalignment can cause the strip edges to be welded 
out of registry. As a result, the tube forming process must be closely 
monitored and the tube fabrication process be stopped when a twist in the 
seam being formed is detected. 
Attempts to solve this problem are taught by Crawford in U.S. Pat. No. 
2,936,357, Kato et al, U.S. Pat. No. 4,299,708 and by Nakako in Japanese 
Application 99224. All three disclose a rolling seam guide in the form of 
an annular fin. Kato et al. and Nakako teach that the annular fin is 
provided on the internal surface of one or more of roll just prior to 
welding. These rolls serve as tube forming rolls and seam guides. 
Although these rolling seam guides reduce the galling and deformation of 
the edges forming the seam, problems are still encountered. The invention 
is a mechanism for removing the twist in the metal strip as it is being 
shaped into a tubular form which substantially eliminates the galling and 
deformation of the edges as they are being guided by the seam guide and 
effectively assures that the edges of the metal strip are not misaligned 
when welded. 
SUMMARY OF THE INVENTION 
The invention is a mechanism and method for counteracting and removing a 
twist in a rolled metal strip being formed into a tube by a tube forming 
machine. The mechanism has a mounting bracket mountable to the tube 
forming machine and a frame rotatably attached to the mounting bracket. 
The frame is rotatable about a longitudinal axis concentric with the axis 
of the rolled metal strip. At least one pair of edge rolls are attached to 
the frame. Each of the edge rolls is rollingly engageable with a 
respective one of the longitudinal edges of the rolled metal strip. At 
least one pair of backing rolls are also attached to the frame. The pair 
of backing rolls is engageable with the side of the rolled metal strip 
opposite the side engaged by the edge engaging rolls. The pair of backing 
rolls inhibit the transverse displacement of the rolled metal strip by the 
pair of edge rolls. Means are provided to rotate the rotatable frame about 
its longitudinal axis to align the longitudinal edges of the rolled metal 
strip with a seam guide. This alignment of the edges of the metal strip 
with the seam guide prevents galling or deformation of the longitudinal 
edges by the seam guide when a twist occurs in the rolled metal strip. 
One advantage of the twist counteracting mechanism is that it prevents 
deformation of the edges of the metal strip when a twist occurs. This 
results in a more uniform welded seam. 
Another advantage is that the twist counteracting mechanism provides a 
rolling engagement with the longitudinal edges of the rolled metal strip, 
thereby reducing galling of the longitudinal edges. 
Still another advantage is that the twist counteracting mechanism may be 
adjusted without stopping the tube forming mechanism. 
These and other advantages will become more apparent from a reading of the 
detailed description of the invention in conjunction with the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows the main components of a machine 10 for continuously producing 
seam welded tubing from a flat metal strip 12. The machine 10 has a 
machine frame 14 which may be oriented in a vertical direction, as shown, 
or may be horizontally oriented as is known in the art. At least one set 
of forming rolls, illustrated by rolls 16 and 18, are rotatably mounted on 
the machine frame 14 and roll the flat strip 12 into a cylindrical form as 
it passes through the machine in the direction indicated by arrow 20. As 
is known in the art, the flat metal strip 12 is supplied to the machine 10 
as a continuous metal strip from a spool, not shown. Although only two 
forming rolls, rolls 16 and 18 are shown, it is understood by those 
skilled in the art, that more than one set of forming rolls are normally 
required to roll the flat metal strip into a cylindrical or tubular form. 
The machine 10 preferably has a seam guide 22 which aligns the edges 24 and 
26 of the rolled metal strip with a welder 28. A final set of closing 
rolls, such as rolls 30 and 32, close the seam 34 formed by the edges 24 
and 26 of the metal strip 12 just prior to being welded to each other by 
the welder 28. The welder 28 welds the edges 24 and 26 to each other to 
continuously produce seam welded tube 36. 
A twist counteracting and removing mechanism 38 is mounted to the machine 
frame 14 between the seam guide 22 and the set of forming rolls 16 and 18. 
As shown more clearly in FIGS. 2 and 3, the twist removing mechanisms 38 
has at least one pair of edge rolls 40 and 42 which rollingly engage the 
edges 24 and 26 of the metal strip 12 as it is being formed and align them 
with the seam guide 22. It is recognized that a duplicate pair of edge 
rolls 40 and 42 may be used if necessary or desired to increase the 
effectiveness of the twist counteracting mechanism. The edge rolls 40 and 
42 engage the edges 24 and 26 in a direction substantially parallel to the 
edge surfaces. The edge roll 40 is attached to a first annular end member 
44 while edge roll 42 is attached to a second annular end member 46 which 
is longitudinally spaced from the first annular end member 44. The annular 
end members 44 and 46 are rigidly connected to each other by a bridge 
member 48 to form a rotatable frame 50 (FIG. 1). The bridge member 48 may 
be a flat plate, but preferably is a curved plate as shown substantially 
mating with the outside diameters of the first and second end members 44 
and 46. The annular end members 44 and 46 have axially aligned through 
apertures 52 and 54 respectively through which the rolled metal strip 12 
passes, as shown. The axes of the axially aligned through apertures 52 and 
54 define a longitudinal axis 56 which is concentric with axis of the tube 
36 as it is being formed by the machine. 
A first pair of backing rolls 58 and 60 are provided upstream of the edge 
rolls 40 and 42, while a second pair of backing rolls 62 and 64 are 
provided downstream of edge rolls 40 and 42. The backing rolls 58-64 are 
disposed on the side of the rolled metal strip 12 opposite the edge rolls 
40 and 42 and support the rolled metal strip 12 concentric with the axes 
of through apertures 52 and 54. The backing rolls 58-64 engage the rolled 
metal strip and prevent it from being transversely displaced or from being 
misaligned by the forces applied to the edges 24 and 26 by edge rolls 40 
and 42. Preferably, backing rolls 58 and 60 and backing rolls 62 and 64 
are disposed at 90.degree. relative to each other and are equally spaced 
on opposite sides of a plane defined by the seam 32 and the longitudinal 
axis of the tube 36 being formed. The rolls 58-64 may be attached to the 
bridge member 48, or they may be attached to respective annular end 
members 44 and 46. 
Although two sets of backing rolls, such as backing rolls 58 and 60 and 
backing rolls 62 and 64 are preferred, it is recognized that a single set 
of backing rolls may be used. In this arrangement, backing rolls may be 
located intermediate the edge rolls 40 and 42. 
The rotatable frame 50 is rotatably mounted to the machine frame 14 by a 
mounting bracket 70 (FIG. 2). The mounting bracket 70 is attached to the 
machine frame 14 and supports the rotatable frame 50 so that the 
longitudinal axis 56 of the through apertures 52 and 54 is concentric with 
the longitudinal axis of the tube 36 as it is being formed. The first 
annular end member 44 has an annular boss 72 which is concentric with the 
longitudinal axis 56. The annular boss 72 is rotatably received in a guide 
aperture 74 provided in mounting bracket 70. The first annular end member 
44 has three equally spaced arcuate slots such as arcuate slot 76. 
Fasteners such as bolts 77 (FIG. 3), pass through the arcuate slots 76 and 
are received in threaded bores such as threaded bore 78 provided in the 
mounting bracket 70 to rotatably secure the rotatable frame 50 to the 
mounting bracket 70. The arcuate slots permit limited rotation of the 
rotating frame 50 relative to the mounting bracket 70. 
An arm 80 (FIG. 2) is attached to the first annular member 44 and extends 
radially therefrom substantially parallel to the surface of the machine 
frame 14. 
The arm 80 has a tab 82 provided at its free end. The tab 82 has an open 
ended slot 84 which receives a necked down portion 86 of an angle 
adjustment screw 88 as shown in FIG. 4. The adjustment screw 88 is 
threadably received in a threaded bore provided in a screw block 90 
attached to the mounting bracket 70. A spring washer 92 maintains the tab 
82 of arm 80 against the shoulder 94 formed by the necked down portion 86 
of adjustment screw 88. 
The angular orientation of the rotatable frame 50 relative to the machine 
frame 14 and the edge rolls 40 and 42 relative to the edges 24 and 26 of 
the tube being formed may be adjusted by rotating adjustment screw 88 in 
either a clockwise or counterclockwise direction as required. 
In operation, the edge rolls 40 and 42 engage the edges 24 and 26 of the 
rolled metal strip 12 at a location immediately prior to being aligned 
with the welder 28 by the seam guide 22. The operator will observe the 
edges 24 and 26 as they pass the seam guide 22. If a gap exists between 
seam guide 22 and one of the edges 24 or 26 or if the gaps between the 
seam guide 22 and the edges 24 and 26 are unequal due to a twisting of the 
metal strip 12 as it is being formed, the rotatable frame 50 and the 
attached edge rolls are rotated by adjustment screw 88 until the gaps 
between seam guide 22 and the edges 24 and 26 are eliminated or if gaps 
between the seam guide 22 and the edges 24 and 26 remains, until the gaps 
between the seam guide 22 and the edges 24 and 26 are substantially equal. 
This eliminates unequal forces from being applied to the edges of the 
metal strip 12 by the seam guide 22, which otherwise would gall or deform 
the edges. 
Since a twist is removed by rollers 40 and 42 which rollingly engage the 
edges 24 and 26 of the metal strip 12, the deformation of one or the other 
of the edges is significantly reduced. Because the twist counteracting 
mechanism can be adjusted without stopping the mechanism for producing 
seam welded tubing, it further eliminates the need to shut down tube 
making process to correct for the twisting of the partially formed rolled 
metal strip due to imperfections. 
It is not intended that the invention be limited to the specific embodiment 
shown in the drawings and discussed in the specification. It is recognized 
that those skilled in the art may make certain changes or improvements to 
the disclosed embodiment within the scope of the invention as set forth in 
the appended claims.