Method and apparatus for processing continuously manufactured tubing

A continuously fed tube is momentarily halted at a cutting station and quickly cut by a rotating knife. The tube is continuously advanced from driving rollers to idler rollers and passes through intermediate pinch rollers which are cam controlled in synchronism with the cutting process to bow the tube at a rate which causes the tube portion at the cutting station to briefly stop during cutting. The cutter includes a planetary gear set having a carrier rotatable about a central axis which carries a knife for rotation about another axis while it revolves about the central axis. The knife makes many rotations per carrier revolution but is in position to cut the tube during one of the rotations.

FIELD OF THE INVENTION 
This invention relates to a method and apparatus for processing 
continuously manufactured tubing and particularly to a method and 
apparatus for feeding a continuously advancing tube for processing at a 
stationary site. 
BACKGROUND OF THE INVENTION 
In the manufacture of tubing, a continuous tube is emitted from a tube mill 
at a high speed and the tube is cut into desired lengths as needed for 
specified usage or for convenient storage or shipping. The conventional 
cutting method uses a guillotine type cutter which chops the tube in a 
downward motion and is then retracted by an upward motion. In order not to 
interfere with the continuous advance of the tube, the knife, carried on a 
shuttle, moves in the direction of tube advance during cutting and 
retracting. Then the shuttle must return the knife to a start position for 
the next cut. Thus the alternating motion in two directions, forward and 
back motion of the shuttle and knife as well as up and down motion of the 
knife, is inefficient from the standpoint of overcoming inertia when 
reversing the movements. The inertia is substantial due to the 
considerable mass of the cutting mechanism. In addition, the time required 
for such cutting procedure places a limit on the production rate of the 
tubing. 
It has been proposed to use a rotary knife motion for such purposes wherein 
a knife is moved in an arc during the cut and is then stopped and 
restarted in time for the next cut. In this case, the inertia of the knife 
must be overcome twice for each cut. That proposal does not overcome the 
need to shuttle the knife mechanism back and forth to accommodate tube 
motion during the cut. 
SUMMARY OF THE INVENTION 
It is therefore an object of the invention to provide a method and 
apparatus for feeding a continuously supplied tube in a manner to briefly 
stop it at an operating station. It is another object to provide such a 
method and apparatus for feeding a continuously manufactured tube to a 
stationary station for an operation in a fixed plane. 
The method of the invention is carried out in a process for the continuous 
manufacture of an elongated tube by the method of momentarily stopping the 
tube at an operation station comprising the steps of; guiding the 
elongated tube through a travel path prior to the operation station, 
periodically increasing the length of the travel path, controlling the 
rate of the path length increase to momentarily stop the advance of the 
tube to the operation station while feeding of the tube into the travel 
path continues, whereby for the duration of the stop a portion of the tube 
at the operation station is essentially stationary to facilitate an 
operation thereon. 
The invention is also carried out by apparatus for momentarily stopping a 
portion of a continuously fed tube in an operation station for performing 
an operation thereon comprising; an operation station, driving rolls for 
continuously advancing a tube in the direction of the operation station, 
idler rolls between the driving rolls and the operation station, means for 
bowing the tube including a guide between the idler rolls and the driving 
rolls for moving the tube laterally, and control means for moving the 
guide at a rate with respect to the tube advance rate sufficient to 
momentarily stop the tube advance at the idler rolls while the tube is 
continually advanced at the driving rolls.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The tube feeding method and apparatus to be described are especially 
designed for facilitating tube cutting at a stationary station, however 
they also apply to other tube processing which can be done quickly at a 
stationary location. The invention recognizes that the cutting mechanism 
has greater inertia than the tube so that it is preferable to accelerate 
the tube rather than the cutting mechanism. The tube is accelerated 
laterally to bow the tube. The bow is described as a simple arcuate curve 
but may also be an S-shape or other curve. 
Referring to the drawings, the cutter wheel 10 comprises a rotatable 
support 12 driven by a motor 14 for rotation about an axis 16. A knife 18 
is pivotably mounted for rotation about an axis 20 and is rotatably driven 
by means to be described. The knife 18 is elongate and has a blade 22 at 
one end and a counterweight 24 at the other end. The blade 22 extends 
beyond the periphery of the support 12 when the knife is angularly 
disposed with the blade outward but the counterweight does not ever extend 
beyond the support. The tube 26 to be cut is shown in section in FIG. 1 
and is a flat thin walled tube of metal such as aluminum which is readily 
cut by a single stroke of a rapidly moving blade. Preferably the blade is 
a well known structure called a Vogal knife which has a central cusp 28 
for piercing the top of the tube and a curved concave blade portion 30 on 
either side of the cusp 28 for slicing through the side walls of the tube. 
The knife 18 is arranged to rotate about its axis 20 several times for 
each rotation of the support 12. An intermediate knife position is shown 
at 18'. The knife is in position to intersect the path of the tube 26 only 
once during each rotation of the support 12 and the successive knife 
rotations are idle, allowing time for the tube to advance to the next 
desired cut-off point. 
The tube preferably originates from a tube mill, not shown, and advances at 
a constant preset speed. As shown in FIG. 2, the tube 26 is advanced by 
drive rollers 32, operated by a motor 34 and is guided toward the cutter 
station by idler rollers 36. The cutter station comprises the vicinity of 
the cutter wheel 10 and has two sets of die blocks 38 spaced on opposite 
sides of the path of the blade 22 for positioning and supporting the tube 
26 during the cut. For the purpose of momentarily stopping the tube 
advance at the idler rollers and at the cutting station, a pair of pinch 
rollers 40 engage the tube midway between the drive rollers 32 and the 
idler rollers 36. The pinch rollers 40 are mounted on a slide 42 or the 
like for movement in a direction transverse to the tube advance movement. 
The slide 42 carries a cam follower 44 which is driven by a cam 46. The 
cam 46, in turn is rotated by a servomotor 48 controlled by a control 
circuit 50. The control circuit 50 also controls the motor 14 and has an 
input from a position encoder 52 on the motor 14 which reveals the cutter 
wheel position to the control circuit. 
While the constant feed of the tube prevents stopping the tube altogether, 
transients can be introduced to the path of the tube to cause a momentary 
halt or hesitation of the tube at the idler rollers 36 without any 
disturbance to the constant feed at the drive rollers 32. By increasing 
the effective path length between the drive rollers and the idler rollers 
at the same rate as the tube feed, the tube advance at the idler rollers 
36 is stopped for as long as the increase of path length can be sustained. 
Then if the path length is decreased to return the tube to the original 
path, the tube speed at the idler rollers will temporarily be higher than 
the normal speed. The cam, driven by the servomotor 48, is under control 
of the circuit 50 to rotate when the cutting action is about to take place 
thereby causing the pinch rollers 40 to bow the tube 26. The servomotor 
speed and the cam shape are calculated to effect the rate of displacement 
necessary to offset the advance during the increase of the path length so 
that the tube will be stationary at the cutting station for a brief time. 
Typically the tube mill can be expected to produce tubing at a rate of 600 
feet per minute. Assuming the tube is to be cut at 2 foot lengths, the 
wheel speed will be 300 rpm. For a distance of 10 inches between the two 
axes of rotation and a knife length of 6 inches from its axis to the 
cutting edge, the linear velocity component due to the wheel rotation will 
be 500 inches per second. If the knife rotates at 3000 rpm, that adds a 
velocity component of 1800 ips. If the tube height is 13/8 inch and the 
blade height is 2 inches, the knife will be in contact with the tube for 
0.00143 seconds. During that time the tube advance would be 0.172 inch. 
For a separation of six feet between the rollers 32 and 36, a bowing 
displacement of about 2.5 inch is adequate to produce the increased path 
length. 
The details of the cutting wheel are shown in FIG. 3. A planetary gear set 
is used to rotate the knife 18 about its own pivot axis 20 and to revolve 
the knife about the axis 16 of the support 12. The support 12 is the 
planetary carrier for the gear set. A fixed housing 55 has a first 
cylindrical portion 56 which encloses the cuter wheel 10 and a second 
cylindrical portion 57 of greater diameter than the first which has room 
for knife rotation and has ports 58 which permit the tube 26 to pass 
through the cutting station. A stationary internal ring gear 60 is secured 
to the housing by a hollow hub 62. The carrier or support 12 is hollow and 
contains all the gears of the planetary gear set. The carrier has a 
generally cylindrical shape and has a hub aperture 61 which is rotatably 
mounted by bearings 64 on the outer surface of the hub 62. For additional 
support, the carrier has an axle 63 extending opposite the bearings 64 
which is journaled within a tubular boss 65 in the housing 55. A shaft 66 
is journaled in the hollow hub 62 and is driven at its outer end by the 
motor 14 and carries a sun gear 68 at its inner end. A pair of 
intermediate gears 70 are rotatably mounted on the carrier 12 by bearings 
72 and each gear 70 is compound, having a large diameter gear portion 70a 
which meshes with the sun gear and a small diameter gear portion 70b which 
meshes with the internal ring gear. A pair of outer pinions 74 and 76, 
also carried by bearings 78 on the carrier 12, mesh with the large 
diameter gear portion 70a. The pinion 76 is coupled by a shaft 78 to the 
knife 18 for supporting and rotating the knife. 
In operation, the motor 14 drives the sun gear 68 which causes the 
intermediate gears 70 to turn within the fixed ring gear 60 to drive the 
carrier 12. The motor rotation direction is chosen to rotate the carrier 
12 in the cutting direction at the cutting station. The pinion 76 and the 
knife are driven in the same direction so that all the forces join to move 
the knife 18 in the cutting direction. As the carrier makes a single 
revolution, the knife 18 makes many rotations, perhaps 10 or 15, depending 
on the gear ratios selected. During one rotation the knife will be 
positioned by the carrier 12 to cut the tube 26 and during all the other 
rotations the knife will not be in position to touch the tube. Since the 
housing is stationary and no part of the cutter wheel 10 moves in the 
direction of the tube motion, the blade of the knife 18 is restricted to 
movement within a fixed plane and the tube, which is temporarily halted, 
is cut in that plane. The throughput of such a feeding and cutting 
arrangement is on the order of 600 feet per minute whereas the older style 
guillotine cutter and shuttle mechanism limited the throughput to 400 feet 
per minute.