Note: Descriptions are shown in the official language in which they were submitted.
"APPARATUS AND METHOD FOR SPOT ANNEALING TUBING"
Back~round of the Invention
The invention relates to the annealing of tubing and sim-
ilar elongated products such as rods or wires. More par~icularly,
it relates to the annealing of elonqated products on which it is
sometimes desirable to have at leas~ selected portions of ~heir length
in an annealed state. One such product is straight lengths of finned
tubing to be used in heat exchangers. Such tubing has been conven-
tionally processed in short lengths cut frcm a s~raightened portion
of a large coil which has been annealed. The short leng~hs have a
long mandrel inserted in them and are then position2d in a fin rolling
apparstus which is capable sf selectively moving the finning members
into and out of contact with the tubing so that unfinned lands and
ends can be provided. When the unfinned portions are in an annealed
state, the tubes can be more easily assembled into the tube sheet
header and baffle portions of heat exchangers by internal expansion
techniques.
Techniques prev~3usly used ~o anneal such tubes have in-
cluded both batch and continuous techniques. In the batch technique,
the entire coil or ind~vidual tube length must be placed in a furnace
for an extended period. The prooess is very time-consuminy, requires
very expensive capital equipment, and also utilizes a large amount
of energy. Continuous annealing techniques have ~l~so been developed;
one example of which can be seen in Herren et al Patent No. 3,518,405.
In this apparatus, the tubinQ is bent partially around each of a
spaced pair of current-rarrying electrode wheels which cause the por-
tion of the tubing between the wheels to be heated. The electrode
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wheels are typically made of graphite which wears relatively rapid1y,
thus causing a substantial expense in maintenance9 electrode replace-
ment and downtime. Another example can be seen in Judd, Paten~ No.
4,309,887 wherein the entire tube is continuously annealed by an in-
duction heater. Patent 3,708,354 also shows continuous annealing.
Summary of the Invention
It is among the objects of the present invention to provide
an annealing apparatus which can be operated as an integral part of a
high speed continuous finning operation which produces a large number
of short tube lengths from a large coil. It is an additional object
to provide such an apparatus which is relatively compact and simple,
able to operate for extended periods with little maintenance, and
very energy efficient.
These and other objects and advantages are attained by the
apparatus and method of the present invention in which selective or
"spot" annealing of spaced portions along the length of a continu-
ously moving tube can take place at a speed which is at least suf~i-
cient to accommodate a downstream finning operation. However, the ap-
paratus could also be used independently of any downstream operations
to spot anneal plain tube or wire or rod stock. The apparatus in-
cludes an annealing chamber mounted on a reciprocating carriage whichcan move in the direction of the tube or other workpiece. The anneal-
ing chamber contains a pair of spaced, automatically actuated tube
engaging clamps which engage the tubing. During the limited time that
the clamps engage the moving tubing, they cause the chamber and car-
riage to which the are attached to be moved downstream with the tubing.Thus, the spot annealing takes place during the time the carriage is
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moving. Upon release of the clamps, an air cylinder or other means
rapidly returns the carriage upstream to its starting position. A
quenching chamber is preferably mounted on the carriage immediately
downstream of the annealing chamber so that the just-annealed portion
5 of the tubing can be rapidly cooled as th.e carriage returns upstream.
The quenching can prevent post-annealing oxidation and/or discolora-
tion whi1e the injection of an inert gas atmosphere such as nitrogen
into the annealing chamber prevents oxidation and/or discoloration
during annealing. In many, if not most situations in which the re-
sulting spot-annealed tubes are used~ such surface defects would have
no effect on the tube performance. However, since a bright, shiny
tube certainly is more esthetically pleasing ~o a purchaser ~han a
dull, discolored one, it is usually advantageous to use an inert atmo-
sphere and a quench. In order to provide annealed tube sections with
the grain and hardness properties desired, the annealing time and
thus the tube temperature can be selectively controlled, preferably
via electrical relays in response to signals from a mini-computer.
The computer receives its signals from a counter which is actuated by
a wheel encoder which is rotated by the moving tube. The aForemen-
tioned elements which are conventional, ensure that only those por-
tions of the tubing which are to be left unfinned in a downstream
finning operation will be annealed. In a preferred embodiment wherein
annealing is accomplished by resistance heating techniques through
the clamps, the elements also permit arcing to be avoided by actua~
ting the clamps to contact the tube for a small time interval before
and after the current is applied. In two disclosed modifications,
annealing is accomplished by substituting an induction annealing tech-
nique or a radiant gas technique for the resistance annealing techni-
que of the preferred embodiment.
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B _ ~r~ JD~IIlll
Fig. 1 is an isometric view of a preferred embodiment of
the improved annealing apparatus using a resistance heating techni-
que and its rela~ionship to a length of tubing being positively
driven through it;
Fig. 2 is a side view of the apparatus of Fig. l;
Fig. 3 is an isometric view illustrating a modified form
of annealing chamber using an induction heating technique9
Fig. 4 is an isometric view illustrating a modified form
of annealing chamber using a radian~ gas heating ~echnique; and
Fig. 5 is a crosc-sectional view taken on line 5-5 of
Fig. 4-
Detailed Description of the Preferred Embodiment
Referring ~o Fig. ll the annealing apparatus lO includes a
base structure indicated generally at 12. The base includes an upper
fixed support plate 14 and a lower fixed support plate 16. A first
pair of support blocks 20 support a first guide rail member 22, while
a second pair of support blocks 20 supports a second guide rail 22'.
The support blocks 20 attach to the upper support plate 14 by any
suitab1e means such as fasteners. Slidably mounted on the guide ways
or rails 22, 22' are a plurality of spaced guide blocks 24 which are
mounted to the underside of a reciprocable support plate or carriage
member 28. Mounted at the upstream end of the appara~us relative to
a length of tubing 30 being driven in the dir~ction of the arrow is
an annealing chamber 32 which is enclosed with a top plate 33. Im-
mediately downstream of the annealing chamber 32 is a quenching cham-
ber 34 which is also normally enclosed by a cover member 35.
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The carriage assembly 28 including the annealing and quench-
ing chambers 32, 34 is adapted to be reciproca~ed in an axial direc--
tion within the constraints provid2d by guide blocks 24 and guide
rails 22, 22'. Movement in a downstream direction from the position
shown in Fig. 1 is provided by clamping the carriage to the moving
tubing 30 as will hereinafter be described. Movement in an upstrearn
direction is provided by the piston shaft 38 which is anchored to the
carriage by a support block 39 at its upstream or extended end and by
a piston (not shown) movable within the air cylinder 40 at its down-
1~ stream end. The return movement of the piston rod 38 and carriage
2B are achieved by admitting air into the cylinder 40 through hose 41
and permitting it to exit through hose 42. In the downstream direc-
tion, each of the hoses 41, 42 is preferably valved to be in an ex-
haust mode so as to not resist the downstream movement of the car~
riage. Since the carriage may be returned to its upstream end very
rapidly by the air cylinder 40, a hydraulic spring member 44 is pref-
erably provided as a cushion.
The aforementioned positively driven tubing 30 provides the
force for advancing the carriage 28 in a downstream direction. This
is accomplished by a pair of fixed clamp members 52, 52' and a pair of
movable clamp members 54, 54' which are attached to a movable clamp
plate 56 so as to clamp the tubing 30 against the fixed clamp members
52, 52' when the piston shaft 58 of an air cylinder 60 is actuated.
~hen resistance anneal;ng is employed, the fixed clamp members 52, 52'
haYe conductive jaws which are each at a different electrical poten-
tial so as to cause resistance heating of the segment of tubing 30
clamped between them. Also, the clamp members 52, 52' are mounted on
brackets 61 which electrically isolate them from the housing portion
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of the chamber 32. Further~ an insulating plate 62 electrically is~-
lates the movable clamp members 54, 54' from each other and from the
movable plate 56 to which they are attached. Electrical current is
carried to the clamp members 52, 52' by water-cooled electrical cables
66 which are connected at their opposite ends to a transfDrmer assem-
bly 6B. The cables 66 are quite thick and not extremely flexible,
and are preferably supported for movement along with the carriage 28
by a power track assembly 72 which is rigidly attached to the carriage
plate 28 at its upstream upper end and to the lower support plate 16
at its lower end. The links of the power track 72 are pivoted to
each other, thus causing the movement o~ the cable 66 to be very well
constrained. The power track assembly 72 has capacity to support a
number of cable-like members, including the hoses 74~ 75 which supply
air to the clamp cylinder 60.
An inert atmosphere is preferably provided to each of the
chambers 32, 34 from a source such as a nitrogen tank 76. Through ap-
propriate valving (not shown) the gas is directed to the annealing
chamber inlet tube 80 and the quench chamber inlet tube 82. The inert
gas exits the two chambers through the openings at their ends 32' 34'
through which the tubing 30 passes. The quench chamber 34 includes a
water inlet nozzle 86 which preferably is fashioned so as to direct
watcr to all portions of the periphery of the tube. This quench water
ls removed from the chambPr through an outlet drain opening 88.
The tubing 30 is guided for movement away from the anneal-
ing apparatus 10 by a funnel-shaped exit guide 92. The downstream
handling of the tubing forms no part of the present invention and
could comprise appropr-iate structure for finning the spot annealed tubing
on a continuous basis or simply structure to cut ~he ~ubing into short
lengths or to recoil it. The tubing 30 is positively driven when it
enters the annealing chamber 32 through opening 32'. It is preferably
supplied in a large coil (not shown) and is passed through a series of
straightening rollers 94, at least some o~ which are powered. The
straightened tubing is passed thorough a wheel encoder device 96 whose
wheels are rotated by the moving tube to generate counter pulses repre-
sentative of tube displacement in a counter 98. A control panel 100
may contain appropriate controls to manually operate the apparatus 10.
Preferably, however, ~he counter pulses generated by the counter 98,
which are representative of tube displacement9 are fed to a computer
apparatus (not shown) which i5 programmed tc operate the clamp cylin-
der 60, the return cylinder 40 and the application of power to the
clamps. To prevent arcing when resistance annealing is employed5
power i5 not directed to fixed clamp members 52, 52' until after cyl-
inder 60 has been actuated to force the movable clamp portions 54, 54'
against the tube. Similarly, the power to the fixed clamps is cut
before the clamp cylinder 60 is released.
The annealing apparatus of the invention can e~ploy differ
ent techniques o~ annealing other than resistance such as induction an-
nealing and radiant gas annealing and can be designed such that the
power inputs, the travel times of the carriage and tubing while power
is being applied, and the annealing temperature can be varied for
various annealing requirements. In the case of resistance annealing,
the power can be varied by selecting a suitable transforlner 68 which
has adjustable taps. A suitable annealing temperature f~r copper
tubing is 1200F which produces an annealed area between the clamps
having a 15 grain size and a Rockwell 15T hardness of 57-60. Obviously,
when resistance annealing at a particular tube velocity, the power ap-
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plied must be sufficient to produce the desired tube temperature and
will vary depending upon the tube density, the distance between ~he
c1amps 52, 52', and the time duration of heat application. Since the
time duration is limited by the tube velocity and the maximum travel
S capability of the carriage member 28, it is rela~ively si~ple to ex-
per;ment when setting up the apparatus for a particular ~ube, until a
power tap is found which can achieve the required ~emperature in the
carriage travel available and then to provide variations in ~he time of
power application until an exact temperature is achieved. The quench
water admitted through nozzle 86 preferably flows continuously with a
variable flow rate. Similarly9 the nitrogen purge through pipes 80,
82 is atso continuous with a variable flow rate.
The foregoing description relates to a preferred embodiment
of a spot annealing apparatus in which resistance annealing is
accomplished by passing electrical current into the spaced clamp
members 52, 52' and through the portion of the tubular workpiece 30
which is clamped by them. It should be noted, however, that other
annealing techniques could be substituted for the resistance
technique without substantially changing the apparatus shown in
Figs. 1 and 2.
Figure 3 shows a general arrangement for an induction
annealing cha~ber 132. Components of this chamber include a pair
of stationary tube clamps 152, 152', a pair of power actuated
mo~able tube clamps 154, 154', and a water cooled induction annealing
coil 188. The clamps engage the moving tubing 130 and cause the
annealing chamber and carriage to be moved downstream with the tubing
while annealing is taking place via the water cooled annealing
coil 188 which surrounds the portion of tube between clamps.
The tube clamps are engaged prior to applying an inductive
field to the tubing and also current is removed prior to clamp
release in order to assure safety and tube quality. All other
construction oF the annealing chamber and the control movements
of the carriage are similar to that described for the resistance
spot annealer. The annealing coil is shown as comprising attached
helically wound current carrying bar portions 188' which are
joined to electrical cables 166 and a tubular water circulating
portion 188" connected to water supply and discharge tubes ~90, 190'.
Figures 4 and 5 show a general arransement of a radiant
annealing chamber 232 employing natural gas combustion to accomplish
spot annealing of a tube 230. Components of this chamber include
a pair of stationary tube clamps 252, 252', a pair of power actuated
movable tube clamps 254, 254', and a water cooled tubular burner
housing 291 located longitudinally between tube clamps, said
housing having longitudinal rows of spark plug ignited gas burners
292 mounted around its reflective inner surface 293. As in the
aforementioned annealing techniques, the clamps engage the moving
tubing 230 and cause the annealing chamber and carriage to be moved
downstream with the tubing while annealing is taking place in the
radiant tube burner housing. In general, all other construction of
the annealing chamber and the control movements of the carriage, are
similar to that described for the resistance spot annealer. The
gas burners 292 may be suitable premix burners such as those sold
by North American Mfg. Co. of Cleveland, Ohio. They are preferably
mounted in gas receiving manifolds 294 so as to extend through
the outer wall of the housing 291 and the reflective inner wall
293. Excess heat within the walls of the housing 291 is carried
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away by circulating water which enters pipe 295 and leaves by
pipe 269. If desired, vent hoses can be attached to the interior
of the burner housing 291 to vent any fumes.
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