Automatic welding apparatus

An automatic welding apparatus is comprising a replaceable jig table, a conveying device for carrying the jig table between a setting station and a welding station and temporary welding device mounted on the jig table for applying temporary welds to a workpiece while the jig table is being moved by the conveying device. At least one holding device at the welding station removes the temporarily welded workpiece from the jig table and holds the workpiece therein and an additional welding device is positioned with respect to the holding device for permanently welding the workpiece while the workpiece is held by the holding device and the jig table is being returned to the setting station by the conveying device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an automatic welding apparatus for use with a 
workpiece comprising plural divided parts, and which is so operated that 
the parts are first fixed with a temporary weld to form an integral unit, 
and the integral unit is then additionally welded to form a workpiece 
product. 
2. Description of the Prior Art 
In welding apparatus, as disclosed in Japanese Patent Publication No. Sho 
56-7473, for instance, a jig table for workpiece setting is reciprocated, 
by means of a conveying means which extends in the front to rear 
direction, between a welding station in the front and a setting station in 
the rear. A first welding means for temporary welding and a second welding 
means for additional welding are provided at the welding station and 
operate alternatively. Thus, after a workpiece set on the jig table is 
temporarily welded by the first welding means, the jig table is moved 
upwards so that the workpiece may be transferred to a workpiece holding 
means provided at an upper portion of the welding station. After the 
transfer of the workpiece, the jig table is moved back to the setting 
station, and during this time, the workpiece, held by the holding means, 
is additionally welded by the second welding means, and during the 
additional welding operation, a setting operation of the next workpiece on 
the jig table may be carried out at the setting station. 
This type of welding apparatus, however, is inconvenient in that the next 
additional weld on the next workpiece cannot be carried out unless 
procedural steps are completed, after the completion of the additional 
welding. Specifically, the jig table is moved to be introduced into the 
welding station, and thereafter, the temporary weld is made on the earlier 
workpiece and the transfer thereof to the holding means by elevating of 
the jig table is carried out. 
SUMMARY OF THE INVENTION 
It is the primary object of the present invention to provide an automatic 
welding apparatus which substantially reduces the time for welding a 
workpiece. 
It is another object of the present invention to provide an automatic 
welding apparatus in which temporary welds are applied to the workpiece 
during the time that the workpiece is being conveyed from a setting 
station to a permanent welding station. 
It is still another object of the present invention to provide an automatic 
welding apparatus in which a jig table includes a detachably mounted jig 
body such that the jig body can be easily changed for different 
workpieces. 
It is still a further object of the present invention to provide an 
automatic welding apparatus which includes a plurality of holding means 
for holding various types of workpieces wherein the holding means being 
used can be changed in correspondence to the workpiece being welded. 
The present invention is directed to an automatic welding apparatus 
comprising a replaceable jig table, a conveying device for carrying the 
jig table between a setting station and a welding station and temporary 
welding device mounted on the jig table for applying temporary welds to a 
workpiece while the jig table is being moved by the conveying device. At 
least one holding device at the welding station removes the temporarily 
welded workpiece from the jig table and holds the workpiece therein and an 
additional welding device is positioned with respect to the holding device 
for permanently welding the workpiece while the workpiece is held by the 
holding device and the jig table is being returned to the setting station 
by the conveying device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, a jig table 1 is provided for setting a 
workpiece, and a conveying means 2 reciprocates the jig table 1 between a 
welding station B in the front and a setting station A in the rear. The 
jig table 1 comprises a jig body 4 having plural setting members 3 such as 
positioning pins, and clamp members or the like for positioning and fixing 
plural divided parts of a workpiece W. The jig body 4 is detachably and 
replaceably attached to a jig base 6 supported on a carrier 5, through a 
replacement mechanism arranged to be operated by attaching and detaching 
cylinders 7. The conveying means 2 comprises a pair of right and left side 
plates 8 extending in the front to rear direction between the two stations 
A and B. Each of the side plates 8 is provided on its inside surface with 
a guide rail 9 and a conveying chain 10 extending in the lengthwise 
direction thereof. The carrier 5 is provided between the two side plates 8 
and is movably supported by plural guide rollers 5a on each side of a 
guide rail 9 and is connected through a connecting member 5b to the chain 
10 on each side. The reciprocating circulation driving of each chain 10 
gives the carrier 5, and accordingly, the jig table 1 a reciprocating 
movement between the setting station A and the welding station B. 
Additionally, the jig base 6 is tiltably supported on the carrier 5, and 
each cam plate 11, which has a cam groove 11a which is inclined downwards 
and rearwardly and continues to each guide rail 9, is tiltable, as shown 
clearly in FIG. 4. At the setting station A, the cam 11 is positioned 
inside the rear end portion of each side plate 8 so that if the jig table 
1 is returned to the setting station A when each cam plate 11 is raised 
upright and each of the protruding guide rollers 6a are on both sides of 
the rear end portion of the jig base 6 and may be inserted into each cam 
groove 11a. Thereby, the jig base 6 may be tilted rearwards and downwards 
about its pivot portion 6b, and as a result, the setting of a workpiece on 
the jig body 4 at the setting station A can be carried out easily by a 
worker in an easy, comfortable posture. 
At the time of replacement of the jig body 4, the jig table 1 is returned 
to the setting station A from the welding station B in a state that each 
cam plate 11 is down so that a pin 5d arranged to be moved with a lock 
cylinder 5c, provided on the carrier 5, is brought into engagement with 
the jig base 6, as shown in FIG. 6. This keeps the jig base 6 in its 
horizontal posture and carries out the replacement thereof. A cylinder 11b 
rises and falls with the cam plate 11. 
Each conveying chain 10 extends between a driving sprocket 10a and plural 
idle sprockets 10b provided on each side plate 8 and is driven to 
circulate in either the forward or reverse direction. A pair of the 
driving sprockets 10a, provided on the two side plates 8, are 
interconnected through a synchronizing shaft 10c so that the two sprockets 
10a may be synchronously driven by a driving motor 10d provided on one of 
the two side plates 8. 
At the welding station B, there is disposed a workpiece holding means 12 on 
an upper side thereof and two additional welding means 13 on both sides 
thereof. The holding means 12 is provided with plural clamp members 12a 
for clamping the workpiece W. The clamp members 12a are on an upper 
portion of a machine frame 14 above the welding station B and extend 
downwards. Each additional welding means 13 comprises an industrial robot 
having welding machines 13a so that the workpiece W, held by the holding 
means 12, may be applied with a predetermined additional weld by the 
machines 13a. 
According to the present invention, the jig table 1 is provided with 
welding machines 15 mounted thereon so that, during the time that the jig 
table 1 is being advanced to the welding station B, the workpiece W on the 
jig table 1 may receive a temporary weld by the welding machines 15. In 
addition, there is an elevating means 16 for elevating and lowering the 
conveying means 2 so that, while the jig table 1 is being reciprocated 
between the two stations A and B, the jig table 1 may be moved upwards and 
downwards. 
A plurality of the welding machines 15 are provided on the jig body 4 of 
the jig table 1 at positions corresponding to respective temporary fixing 
positions of the plural divided parts forming the workpiece W. The 
elevating means 16 comprise a pair of X-shaped link mechanisms which are 
connected to the respective side plates 8, on both sides of the conveying 
means 2. The X-shaped link mechanism on each side comprises a pair of 
links 33 and 34 which are crossed in the form of X and are pivotally 
interconnected at a crossing point 35 of the middle portions thereof. In 
addition, the links 33 and 34 are pivotally tally attached at their upper 
ends to the side plate 8 on the side surface of the conveying means 2, and 
at their lower ends to a stationary frame 36 provided on the lower side of 
the conveyor 2. An upper end pivot portion 33a of the first link 33 is 
arranged to be slidable horizontally along a guide portion 37 provided on 
the side plate 8, and a lower end pivot portion 34a of the second link 34 
is arranged to be moved along a guide portion 39 made in the stationary 
frame 36 by means of a driving source 38 such that the slide plate 8 may 
be moved upwards and downwards. Numeral 33b denotes a lower end pivot 
portion of the first link 33, numeral 34b denotes an upper end pivot 
portion of the second line 34. 
The guide portion 37 provided on the side plate 8 is so constructed that, 
as shown in FIGS. 1 and 2, a movable frame 37b is movable horizontally 
along upper and lower guide rails 37a provided on the side plate 8, and an 
upper end of the first link 33 is pivotally attached to the movable frame 
37b. The guide portion 39 provided on the stationary frame 36 is in the 
form of a long groove, and the lower end pivot portion 34a the second link 
34 is in slidable engagement therewith through a movable member 39a 
mounted on the same shaft. A piston rod 38a extending from a cylinder 
functions as a driving source 38 and is connected to the pivot portion 
34a. 
A delivery means 17 is provided for delivering the workpiece W, which has 
received additional welds at the welding station B, from the jig table, to 
a discharging station C in front thereof. As shown in FIG. 3, the means 17 
comprises a carrier 17a supported on guide rails 18 extending between the 
two stations B and C. A receiving member 17c for the workpiece W is 
mounted on the carrier 17a by means of a cylinder 17b which is movable 
upwards and downwards, and the carrier 17a is connected to the jig table 1 
by a connecting rod 17d so that the carrier 17a has a reciprocating 
movement between the discharging station C and the welding station B, in 
response to the reciprocating movement of the jig table 1 between the 
welding station B and the setting station A. 
The operation of the foregoing apparatus is as follows: 
First, the plural divided parts comprising the workpiece W, are set on the 
jig table 1 located at the setting station A. Thereafter, the conveying 
means 2 and the elevating means 16 are operated synchronously, and 
thereby, the jig table 1 is moved to advance to the welding station B 
while being moved upwards, and at the same time, that is, during moving of 
the jig table 1, the workpiece W is temporarily welded by the welding 
machines 15 on the jig table. At the time of completion of the advance 
movement of the jig table 1, the jig table 1 reaches a predetermined 
workpiece transfer position which meets the workpiece holding means 12 
provided on the upper portion of the welding station B, and at the same 
time, the temporary welding of the workpiece W is completed. Thus, the 
time lag is eliminated which is caused by either temporary welding or 
upward movement of the jig table 1 to the workpiece transfer position from 
the completion of the advance movement of the jig table 1 and, therefore, 
the transfer of the workpiece W to the holding means 12 from the jig table 
1 can be carried out at a high efficiency. 
After the completion of the transfer of the workpiece, the jig table 1 is 
returned to the setting station A by an operation which is the reverse of 
the above, and at the same time, the workpiece W, held by the holding 
member 12, is additionally welded by the additional welding means 13, and 
in addition, during this welding operation, the next workpiece W is set on 
the jig table 1, which has been returned to the setting station A. 
At this time, the carrier 17a of the delivery means 17 is moved in 
conjunction with the returning means of the jig table 1 so as to be 
introduced into the welding station B to wait for completion of the 
additional welding, and the receiving member 17c of the discharging means 
17 is moved upwards and downwards for receiving a completely welded 
workpiece W thereon from the holding member 12. 
After the receiving of the workpiece product W, the jig table 1 is again 
advanced to the welding station B in almost the same manner as above, and 
the carrier 17a is delivered to the discharging station C for unloading 
the workpiece product W therefrom, and at the same time, the next 
workpiece W on the jig table 1, which has already been subjected to 
temporary welding is transferred to the holding member 12. Thus, by 
repeating the foregoing operations, welding operations of the workpieces W 
can be carried out in succession one step after another. 
Depending on the particular kind or model of the workpiece W, it often 
occurs that the temporary welding thereof is not completed during the 
advance movement of the jig table 1. In this case, after the completion of 
the advance movement of the jig table 1, the subsequent temporary welding 
of the unwelded portions thereof is carried out by the additional welding 
means 13 and thereafter, the workpiece W is transferred to the workpiece 
holding means 12. Even in this situation, the time lag can be extremely 
short, in comparison with a conventional apparatus wherein the temporary 
welding begins after the completion of the advance movement of the jig 
table. 
In order to change the particular kind or model of the workpiece W to be 
welded, the jig body 4 of the jig table 1 and the workpiece holding member 
12 are replaceable with respective predetermined replacements. For this 
purpose, it can be considered that a replacement operation is carried out 
by using a lifting means such as a crane or the like, but this technique 
is low in working efficiency. 
Accordingly, in the illustrated embodiment, respective replacing mechanisms 
for carrying out a replacement operation of the jig body 4 and the 
workpiece holding member 12 at a high efficiency are constructed as 
follows: 
First, the replacement mechanism for the jig body 4 is explained as 
follows: 
As shown in FIGS. 5 and 6, the jig base 6 is provided with an elevating 
frame 19 which is movable upwards and downwards in relation to the jig 
body 4. Additionally, there is a clamp member 20 which is arranged so 
that, by lowering the elevating frame 19, the clamp member 20 is brought 
into engagement with the jig body 4 to press the engaged body 4 for fixing 
it to the jig base 6, and a guide member 21 is arranged so that, by 
elevating of the elevating frame 19, the guide member 21 is brought into 
abutment with the jig body 4 for supporting the jig body 4 so as to be 
laterally movable. 
In more detail, a pair of front and rear L-shaped grooves 4b, which extend 
laterally are formed in the lower surface portion of the jig body 4 so 
that there remains therein respective lower side tab portions 4a. A pair 
of the elevating frames 19 are disposed in a front and rear relationship 
and extend in the lateral direction along the grooves 4b and also each of 
the elevating frames 19 is arranged to be movable upwards and downwards by 
a pair of right and left cylinders 7 attached to the jig base 6. 
Each elevating frame 19 is provided with plural pins 19a arranged to be 
inserted in each groove 4b, and the foregoing clamp members 20 each 
comprise a plate-shaped member which is laterally long and faces an upper 
surface of the tab portion 4a attached to top portions of the pins 19a. 
Additionally, a plurality of first guide rollers 21a, cooperating with the 
guide member 21, are pivotally supported thereon so as to face a lower 
surface of the tab portion 4a, and each of second guide rollers 21b, which 
are arranged to be in abutment with the inner end edge of the tab portion 
4a, is pivotally supported on each pin 19a so that the jig body 4 may be 
supported so as to be laterally movable by the first guide rollers 21a and 
vibrations thereof in the front and rear directions are prevented by the 
second rollers 21b. 
The jig body 4 is additionally arranged so as to be supported on receiving 
seats 6d on the jig base 6, and be set in position by positioning pins 6c, 
on the jig base 6, that are arranged to be mounted in positioning openings 
4c made in the lower surface jig body 4. 
A hook 4d is provided on a lateral side surface of the jig body 4, a 
transformer 22 for the welding machines 15 is mounted on the jig base 6, 
and a receiving base 23 is provided for jig replacement. 
Next, the operation of the foregoing replacement mechanism will be 
explained as follows: 
In an ordinary case, the elevating frame 19 is applied with pressure moving 
it downwards by a downward movement of the attaching and detaching 
cylinders 7, whereby the clamp member 20 is brought into engagement with 
the tab portion 4a for pushing the jig body 4 downwards. Consequently, the 
jig body 4 is fixed, under the pressure, to the jig base 6 while the jig 
body 4 is set in position by the positioning pins 6c. 
When the jig body 4 is to be replaced in correspondence with a change of 
the kind of the workpiece W, the elevating frame 19 is raised by the 
attaching and detaching cylinders 7. The pressed fixing of the jig body 4 
to the tab portions 4a by the clamp member 20 is thus released, and at the 
same time, the guide member 21 on the elevating frame 19 is brought into 
abutment with the lower surface of the tab portion 4a for supporting the 
same. The jig body 4 is lifted upwards to leave the jig base 6 while 
supported on the guide member 21. If the jig body 4 is elevated to a 
position at which the same is apart from the positioning pins 6c, the jig 
body becomes movable laterally. Thus, by pulling on the hook 4d on the 
lateral side surface of the jig body, the jig body 4 can be pulled out 
onto the receiving base 23 on the lateral side thereof. Thereafter, 
another jig body 4 is introduced into a position on the guide member 21 
through the receiving base 23, and the elevating frame 19 is lowered in 
almost the same manner as above so that the jig body 4 may be fixed under 
the pressure thereof to the jig base 6 by the clamp member 20. 
Next, the replacement mechanism for the workpiece holding means 12 will be 
explained as follows: 
As shown in FIGS. 1 and 2, a rotary shaft 24 is provided horizontally on an 
upper portion of the machine frame 14, and a plurality of the workpiece 
holding means 12, for example, three units are provided on a supporting 
member 25. The rotary shaft 24 is arranged to be rotatable by means of an 
index means 26. The index means 26 comprises a rotation driving mechanism 
in which the rotary shaft 24 is arranged to be rotated by a rack 28 
provided on the machine frame 14 meshed with a pinion 27 on the shaft 24. 
The rack 28 is moved forwards and backwards by a cylinder 29. The rotary 
shaft 24 is thus, arranged to be set in position such that a stopper 31, 
provided on the machine frame 14 and directed forward is brought into 
contact with index grooves 30a in an index plate 30 fixed on the rotary 
shaft 24. The index grooves 30a are at three circumferential positions and 
the stopper 31 is movable to be brought into engagement and disengagement 
with any of the index grooves 30a by a cylinder 32. By the cooperation of 
the two mechanisms, the rotary shaft 24 is turned by a predetermined 
angle, and consequently, any desired one of the three workpiece holding 
means 12 is selected to be positioned at an operative position below the 
rotary shaft 24. Thus, a replacement of the workpiece holding means 12 at 
the time of the change of the kind of the workpiece W can be carried out 
at high efficiency. 
Thus, according to the present invention, the jig table is provided thereon 
with welding machines for applying temporary welds to the workpiece set on 
the jig table, and additionally, a conveying means for reciprocating the 
jig table between a setting station and a welding station is arranged to 
be movable upwards and downwards by an elevating means, so that the 
temporary weld and the elevating of the jig table to the predetermined 
position can be carried out while the jig table is moved to advance to the 
welding station. Consequently, a time lag from the completion of 
additional welding to the beginning of the next additional welding can be 
substantially shortened which results in an improvement in productivity, 
as compared with a conventional technique wherein the temporary welding of 
the workpiece and the elevating of the jig table are carried out after the 
completion of the advance movement of the jig table. 
The present invention may be embodied in other specific forms without 
departing from the spirit or essential characteristics thereof. The 
presently disclosed embodiments are, therefore, to be considered in all 
respects as illustrative and not restrictive, the scope of the invention 
being indicated by the appended claims, rather than the foregoing 
description, and all changes which come within the meaning and range of 
equivalency of the claims are, therefore, to be embraced therein.