Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a new and improved
construction of a resistance roll-welding machine -- also
referred to as an electrical resistance-roll seam welding
machine - which is of the type comprising two superimposed elec-
trode rolls to which there is delivered the welding current in
each instance by means of a device for the current transmission
from a stationary part to a rotating part, one of the electrode
rolls being mounted at a pivotably movable overhang arm or
cantilever arrangement, and wherein ther~ is further provided
a transport device for the feed of the workpieces to be welded
to the electrode rolls.
With state-of-the-art resistance roll-welding machines
the welding current is transmitted from a stator forming the
stationary part to a rotor`forming the rotating part, by means
of an electrically conductive liquid, preferably mercury. The
rotor is rotatably mounted upon the stator and the electrically
conductive li~uid is located in a gap between the stator and the
rotor. The electrode roll composed of the stator and the rotor
in this case forms a structural unit with the device for the
current transmission of the welding current.
In the case of a resistance roll-welding machine
comprising two superimposed electrode rolls, by means of which
for instance there are produced longitudinal welding seams at
can bodies or blanks from which there are fabricated cans, with
one electrode roll disposed internally of the blank, due to the
limited space available there is no other possibility for trans-
mitting the current than by means of the stator arranged at one
end of a current-conducting arm and an electrically-conducting
liquid to the rotor of the electrode roll. For reasons of equip-
ment manufacturing convenience the second electrode roll whichbears against the outside of the workpiece, for instance the
can blank or body, is constructed the same as the previously
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discussed electrode roll located internally of the workpiece.
In other words: the electrode roll and the device for the
current transmission from a stationary part to a rotating part --
hereinafter briefly referred to as the welding current-rotary
transmission device -- form a structural unit.
The last-mentioned electrode roll is arranged at
the end of a pivotably movable overhang arm or cantilever, so
that during introduction of the workpieces to be welded between
both electrodes it can deviate. The overhang arm is pivotably
arranged at the machine frame in such a manner that it can move
up and down in a plane which extends in a direction which co-
incides with the feed direction of the workpieces. The electrode
roll which forms a unit with the welding current-rotaty trans-
mission device, possesses a relatively large weight which is
effective at the end of the overhang arm or cantilever. Addition-
ally, the electrode roll is biased, for instance by means o~ a
spring against the workpiece, in order to obtain the necessary
welding force. During the infeed or introduction of a workpiece
between both of the electrode rolls the upper pivotably movable
electrode roll is lifted or raised, for which purpose there is
required a large acceleration force due to the considerable mass
of the electrode roll, and such acceleration force can amount
to more than lifty percent of the welding force. With increased
feed speed of the workpiece the relationship becomes increasingly
more unfavorable. Additionally, during the infeed of a work-
piece between the electrode rolls there are produced furrows
or notches or the like at the starting portion of the workpiece,
which, during subsequent processing of the workpieces, can have
an extremely unfavorable effect or lead to rejects. Since the
trend is to always increase the feed speed of the workpieces,
it can be readily appreciated that increasingly greater diffi-
culties arise owing to the aforementioned problems.
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Therefore, with the foregoing in mind, it is a primary
object of the present invention to provide a new and improved
construction of a resistance roll-welding machine which is not
associated with the aforementioned drawbacks and limitations
of the prior art proposals.
Another and more specific object of the present inven-
tion is directed to reducing the mass of the unit composed of
the overhang arm and the electrode roll, in order to thereby
extensively eliminate all of the previously discussed drawbacks.
Yet a further significant object of the present inven-
tion aims at providing an improved construction of a resistance
roll-welding machine for welding workpieces in an extremely
reliable, rapid and efficient manner, permitting of increased
feed speed of the workpieces while reducing the probability of
forming poor welding seams thereat and reducing the number of
rejects.
Still another significant object of the present
invention resides in the provision of a new and improved construc-
tion of resistance roll-welding machine which is relatively
simple in construction and design, economical to manufacture,
extremely reliable and efficient in operation, not readily
subject to malfunction and breakdown, and requires a minimum of
maintenance and servicing.
Now in order to implement these and still further
objects of the invention, which will become more readily apparent
as the description proceeds, the resistance roll-welding machine
of the previously mentioned type as contemplaced by the inven-
tion, is manifested by the features that the pivotably movable
electrode roll is arranged at an overhang arm which extends
transversely with respect to the feed direction of the workpieces.
The overhang arm or cantilever arrangement is mounted to be
pivotable about a pivot axis or shaft extending in spaced
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relationship from the one electrode roll and transversely with
respect to the axis of rotation thereof. The overhang arm
comprises a housing mounted in the machine frame to be pivotable
about said pivot axis or shaft and a shaft member or shaft
rotatably mounted in the housing, the shaft member carrying at
its free and the one electrode roll. The housing forms the
stationary part and the shaft member the rotating part of the
device for the current transmission. Preferably, the spacing
of the one electrode roll from the overhang arm-pivot shaft is co
considerably greater than the spacing of the housing end con-
fronting the electrode roll from the aforesaid pivot shaft.
With this arrangement and construction of the overhang
arm the welding current-rotary transmission device is displaced
outwardly of the electrode roll with which, according to the
previously mentioned machine of this type, it formed a structural
unit. Thus, the welding current-rotary transmission device is
supported directly at the machine frame in the form of a mass
which is concentrated at the pivot shaft of the overhang arm,
and as a result thereof the mass of the electrode roll which
performs an up and down movement is considerably reduced. Now
the movement of the overhang arm no longer is carried out in a
plane extending in the same direction as the feed direction,
rather in a plane extending ~ransversely with respect to the
feed direction. Due to the outward displacement or shifting of
the welding current-rotary transmission device, constituting the
primary mass, from the electrode roll to the pivot shaft of the
overhang arm located in spaced relationship therefrom, there is
beneficially achieved the result that for the further construc-
tion of the electrode roll there is attained considerable
freedom and the same can advantageously possess a hollow con-
struction for further reducing the mass. A further reduction
in the mass can be realized if according to an advangageous
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furth~r constructional embodiment the shaft member is also of
hollow construction, at the free end of which there is arranged
the electrode roll, and which together with the housing, in
which there is rotatably mounted the shaft member, forms the
pivotably movable overhang arm and the welding current-rotary
transmission device. The current transmission is accomplished
from the housing connected to a current infeed means, through
the intermediary of an electrically conductive liquid such as
for instance mercury, located in a ring-shaped or annular gap
between the housing and the shaft member, to such shaft member
and the electrode roll.
The hollow shaft member or shaft again renders it
possible that, according to a preferred further construction, it
can contain a separate inflow and return flow for the coolant or
cooling agent for cooling the electrode roll. The removal of
the heat which is produced during resistance welding from the
electrode roll heretofore only could be carried out at a reduced
degree of efficiency, in that there was provided an axial bore
in the stator of one such electrode roll, which contained
mercury between the stator and the rotor, and to which there
was conducted the cooling agent, typically cooling water.
However,it has not possible to directly cool the rotor with
cooling water. If, however, there is arranged a hollow elec-
trode roll at the end of the hollow shaft and which contains
an inflow and return flow for a cooling agent, then it is
possible to also cool the periphery of the electrode roll from
the inside of the hollow roll in an extremely exceptional manner.
The shifting of the welding current-rotary transmission
device to the overhang arm-pivot shaft additionally renders it
possible to drive the ~lectrode roll free of play by means of
the hollow shaft. A drive of the electrode roll free of play
is necessary for a resistance roll-welding machine which is
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equipped with a computer control for the regulation of the speed
of the work~iece-feed movement through the transport device and
through the welding rolls. The speed of a drive motor of the
transport device is regulated by means of a computer in such a
manner that thc first weld point or spot always is deposited at an
adjustable spacing from the front or leading end of the workpiece,
for instance a can body or blank, and furthermore, the speed of
the drive motor of the electrode roll, by means of which the work-
piece is further fed or conveyed, is regulated by means of the
computer in such a manner that the last weld point always is
deposited at an adjustable spacing from the rear end of the
workpiece. This speed regulation has the purpose of preventing
that one of the weld points or spots, produced during each half-
wave of the welding current, will be directly deposited upon the
leading or trailing edge of a workpiece, something which easily
can result in scorching or burning of the material at such
locations and rendering exceedingly more difficult further
processing of the workpiece.
According to the invention, a resistance roll-
welding machine for welding workpieces moving along a predetermined
feed direction, comprises: a machine frame; a pair of superimposed
welding roll; a device for transmitting welding current from a
stationary part to a rotating part; overhang arm means extending
substantially transversely with respect to the feed direction
of the workpieces; and means for pivotably mounting the overhang
arm means. The overhang arm means supports one of the electrode
rolls for rotation about a predetermined axis o-f rotation. The
pivotably mounting means includes a pivot shaft about which pivots
the overhang arm means and said one electrode roll. The pivot shaft
is arranged in spaced relationship from said one electrode roll
and extends transversely with respect to its axis of rotation.
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The overhallg arm means com~)rises: a housing; the pivot shaft
pivotably mount~ c3 the housing at the machine frame; a shaft
member; means for rotatably mounting the shaft member in said
housing. The shaft member has a free end carrying said one
elec~rode roll. q'he housing constitutes the stationary part and
the shaft member, the rotating part of the device for the welding
current transmission.
The invention will be better understood and
objects other than those set forth above, will become apparent
when consideration is given to the following detai~led description
thereof. Such description makes reference to the annexed drawings
wherein:
Figure 1 is a schematic frolltview of a resistance
roll-welding machine constructed according to the teachings of
the invention incorporating the overhang arm or cantilever
arrangement and its mounting in the machine frame;
Figure 2 is a top plan view, on a reduced scale,
of the overhang arm and the drive of the electrode roll;
Figure 3 is a cross-sectional view through the
overhang arm of the arrangement of Figure 1, taken substantially
along the line A-A thereof; and ---
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Figure 4 is a sectional view, on an enlarged scale,
through the front end of the overhang arm which carried the
electrode roll.
Describing now the drawings, it is to be understood
that only enough of the structure of the resistance rollwelding
machine of this development has been shown in the drawings in
order to simplify the illustration thereof and to enable those
skilled in the art to readily understand the underlying princi-
ples and concepts thereof~ Hence, as concerns the electrical
resistance-roll seam welding machine, conveniently also referred
to hereinafter as the resistance roll-welding machine, there
will be seen in Figures 1 and 2 only the overhang arm or
cantilever arrangement 10 thereof, which comprises a housing
11 and a hollow shaft 12 which is rotatably mounted in such
housing 11. The hollow shaft 12 which is rotatably mounted in
such housing 11. The hollow shaft 12 is equipped with an elec-
trode xoll or welding roll 13 arranged at the end of such hollow
shaft, and there is further illustrated the drive system for
driving the hollow shaft 12 together with the electrode roll
13. The feed direction for the workpiece 15, which may be for
instance the blank or body of a can, has been indicated by the
arrow B. The angle ~ between the electrode roll 13 and the feed
direction B has been shown exaggerated; a slight inclined posi-
tion of the electrode roll serves to ensure that the edges of the
workpiece 15, for instance the ends of the can blank illustrated
in Figure 1, positively remain in the overlapping position when
the lengthwise edges of the can blank or body 15, according to
the showing of Figure 1, are located between the upper electrode
roll 13 and a rurther electrode roll 17 situated therebelow
and mounted in a welding arm 16, in order for such overlapping
ends to be welded to one another, again as will be apparent
from the showing of Figure 1~
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According to Figures 1 and 2 the housing 11, which
together with the hollow shaft 12 forms the overhang arm or
overhang arm means 10, is pivotably mounted at the machine frame
19 about a pivot axis or shaft 18 extending in spaced relation-
ship from the electrode roll 13 and transversely to its rotational
axls .
As best seen by referring to Figure 2 the spacing a
of the electrode roll 13 from the overhang arm-pivot shaft 18
is considerably greater than the spacing _ of the end of the
housing 11, confronting the electrode roll 13, from the afore-
mentioned pivot shaft 18. The housing 11 with the section of
the hollow shaft 12 located therein constitutes the predominant
part of the weight of the overhang arm 10, since the shaft 12
and also the electrode roll 13 are hollow, as best seen by
referring to Figure 4.
The hollow shaft 12 is rotatably mounted in the
housing il by means of the roller bearings 20 or equivalent
structure. The massive wall and thus heavy housing 11, which
between both of the roller bearings 20 possesses a wall thick
ness extending from outside of the housing 11 up to the hollow
shaft 12, constitutes the stationary part of the device for
the current transmission, whereas the hollow shaft 12 constitutes
the rotary part of this device for the current transmission.
In a ringshaped or annular ga~ 21, which is sealed in any
convenient fashion in axial direction, and which gap 21 is
located between the housing 11 and the hollow shaft 12, there is
containcd an clcctrically conducting liqui~, for instancc mercury,
for transmitting the welding current from the stationary part
to the rotating part of the device for the current transmission.
As best seen by referring to Figure 1, the housing 11 is conduc-
tively connected with a current rail or busbar 22 which extends
from one side transversely over the entire housing 11.
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Furthermore, as also will be seen from Figure 1 the
overhang arm 10 can move up and down, due to its pivotably
movable mounting about the pivot shaft 18, in a plane which is
disposed perpendicular to the can blank or body 15. Since the
hollow electrode roll 13 itself only possesses a low mass,
there thus are not formed any furrows or notches at the edge of
the blank or body 15 during the infeed of such blank between
both of the electrode rolls 13 and 17. The requisite welding
pressure is produced by a spring 23 supported at the machine
frame 19 and effective at the end of the shaft 12.
As will be recognized from the showing of Figures 2
and 3, the hollow shaft 12 contains an inflow means 25 and a
return flow means 26 for a cooling agent, for instance typically
cooling water, for cooling the electrode roll 13. The coolant-
inflow means 25 which extends through an annular space 12a at the
inside of the hollow shaft 12 and the coolant-return flow means
26 which extends through a pipe or line 26a arranged at the
center of the hollow shaft 12 are disposed essentially concen-
trically with respect to one another, and between both such
inflow means and return flow means there is located a ring-
shaped hollow space 27. This concentric arrangement of the
inflow means 25 and the return flow means 26 for the cooling
agent or coolant, with only the hollow space or chamber 27
containing air located therebetween, is selected for the front
part of the hollow shaft 12 which extends up to the electrode
roll 13 in order to thereby beneficially obtain a further
reduction in weight, whereas the rearward part of the hollow
shaft 12 does not possess any hollow space between the inflow
means and the return flow means for the cooling agent.
The hollow shaft 12 is operatively connected by means
of an angularly movable coupling 30, for instance a multiple
disk clutch or coupling, with an intermediate tube or pipe 31
through which extends the inflow means 25 and the return flow
means 26 for the cooling agent in the form of separate and
mutually parallely extending pipes or tubes 32 and 33. At the
region of the coupling 30 there is provided a flexible pipe
connection 34 and 35 for the inflow means and the return flow
means of the cooling agent.
The intermediate pipe or tube 31 is connected by
means of a further angularly movable coupling 36 with a hollow
drive shaft 37 of a transmission or gearing 38 with which there
is flanged a suitable electric drive motor 39, preferably a
stepping motor. The inflow means and return flow means for the
cooling agent extend through the transmission 38 and the hollow
drive shaft 37. The infeed and withdrawal of the cooling agent
is accomplished by means of a rotary throughpassage means of
conventional construction which therefore has not been particu-
larly shown in the drawing. The arrangement and construction of
the drive for the hollow shaft 12, apparent from the showing of
Figure 2, is predominantly selected in this manner because of
space saving considerations, but is would be also conceivable
with another construction of the machine to provide the drive
directly at the end of the hollow shaft 12.
Finally, as will be seen from the showing of Figure 4,
the electrode roll 13 comprises a flange 41 formed of one-piece
with the hollow shaft 12 and a disk body 43 which is connected
by screws 42 or equivalent fastening expedients with the flange
41. The disk body 43 fixedly clamps a ring-shaped electrode 44
between itself and the flange 41. The ring-shaped electrode 44
defines an electrode or welding roll which internally has a
hollow space or chamber 45 which flow communicates with the
infeed means 25 and the return flow means 26 for the cooling agent,
so that the cooling agent can circulate within the electrode
roll and thus has direct contact with the ring--shaped electrode 44
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where there appears the most pronounced heating-up effect.
While there are shown and described present preferred
embodiments of the invention, it is to be distinctly understood
that the invention is not limited thereto, but may be otherwise
variously embodied and practiced within the scope of the follow-
ing claims. ACCOR~INGLY,
