Production machine incorporationg a high-speed lift and carry device with double walking beam, and the production system implementing this type of machine

A production machine equipped with two walking beam lift and carry devices forming two parallel tracks, a main track and a branch track. Transfer of a part from the branch track to the main track is achieved by a handling unit synchronized with the walking beam.

BACKGROUND OF THE INVENTION 
The invention relates to a production machine of the kind described in the 
U.S. patent application 07/413076 of 09.27.1989 now abandoned, which will 
henceforth be called the "Initial Patent". 
The Initial Patent notably describes a walking beam lift and carry device 
enabling palettes to be presented successively on different workstations. 
The system is mainly geared to automatic assembly, the palettes acting as 
support to the product being manufactured, and each workstation 
corresponding to an operation of the process to be performed (insertion, 
welding, crimping, checking, etc.). To this end, each station is equipped 
with a suitable device which will henceforth be designated by the general 
name "working module". 
An essential feature of the type of machine thus achieved is a high degree 
of flexibility, obtained by equipping each module (lift and carry module 
and working modules) with individual motorization, synchronization being 
achieved by electronic control. This control, according to the different 
situations encountered, enables operating cycles to be set in motion at 
the level of each module, when this operation is possible and necessary, 
and enables the module to be left inactive in the opposite case. 
Another feature of the machine lies in its linear configuration, which 
makes it particularly suitable for integration into a production line 
comprising other machines upline and downline, the link between the 
machines being easily able to be achieved by conveyor sections which may 
act a buffer stocks. 
The flexibility of operation described in the foregoing paragraph can 
usefully be taken advantage of: 
at the lift and carry module level to subordinate its operation to the fact 
that certain necessary conditions are correctly met: 
upline feed (presence of a palette against the machine input stop) 
no downline blocking (no accumulation beyond a certain critical point on 
the downline conveyor) 
ability of the working modules to fulfill their function 
at the working module level, to adapt the machine to the different versions 
of the product to be manufactured, by rendering such or such a module 
active or inactive depending on the version involved (the latter being 
automatically identified by reading of a coding at the machine input). 
Thus described by the Initial Patent, a machine of this kind is suited to 
integration in a system with a strictly linear configuration, i.e. 
starting from an empty palette on which the product to be manufactured is 
progressively built up by successive operations. At the end of the 
process, the finished product is removed from the palette, which is then 
recycled back to the machine at the head of the line. 
In pure theory, such a system could be achieved by a single machine 
presenting the required number of workstations. In practice, this number 
is generally such that several machines have to be placed in series linked 
by conveyor devices, as described above. 
A linear system of this kind can be advantageously used whenever the range 
of operations to be carried out permits, which is not always the case. 
Certain constraints may in fact arise, notably in the assembly field, 
which cannot always be met by the linear configuration: 
A product incorporating distinctly individualized sub-assemblies, each 
sub-assembly having to be subjected to a very specific process before 
being incorporated in the main product. The production line then becomes 
tree-structured (in the same way as the range), i.e. it is composed of a 
main line leading to the finished product, and of one or more branch 
lines, each of these lines being dedicated to a given sub-assembly. 
The presence of operations which, for technical reasons, cannot be carried 
out on the palettes conveying the main product (for example, shaping or 
welding operations which absolutely must be performed before insertion in 
the main product for reasons of accessibility or pollution). 
The object of the type of machine involved in the present invention is to 
solve the problems set out above. We will first of all examine the first 
one, and will see that the second one is no more than a particular case. 
When a sub-assembly is manufactured on a branch line, the latter may be 
equipped with conventional machines, depending on the operations to be 
carried out. But it must end with a special machine, which is common with 
the main line, and whose essential function is to transfer the finished 
sub-assembly to the main product being manufactured. Such a machine will 
henceforth be designated "convergence station". On the main line, it can 
occupy any position (generally along the line, but it may be at the head 
or at the end of the line in certain cases). On the branch line, it must 
occupy the end-of-line position, i.e. the corresponding palettes leave it 
empty and are recycled to the machine at the head of the branch line. 
SUMMARY OF THE INVENTION 
According to a first embodiment of the invention, a convergence station is 
characterized by the presence of two walking beam lift and carry devices 
disposed parallel to one another and operating in opposition (when one 
lifts upline, the other carries downline, and vice-versa). The two devices 
are therefore mechanically distinct, as far as the cam kinematics are 
concerned, their motorization on the other hand being able to be common, 
if this provides an advantage in simplicity. 
One of the devices incorporated in the main line, and the other in the 
branch line, will be designated respectively by "main track" and "branch 
track". 
The machine must naturally be completed by a transfer handling unit 
disposed transversely to the lift and carry devices, and operating at the 
same rate. This handling unit, of the Pick and Place type, picks the 
sub-assembly up from a palette of the branch line, and places it on the 
main product, itself carried by a palette of the main track. The 
synchronization of the assembly must be such that the "Pick" and "Place" 
operations take place at the right time in the two walking beam cycles. 
This is moreover the reason why these cycles have to be in opposition. 
According to another embodiment of the invention, the two walking beam 
devices no longer operate in opposition, but in phase. This particularity 
introduces an important simplification, insofar as a single mechanism is 
then sufficient for the assembly. However, this gives rise to a problem 
with the transfer handling unit. As the two tracks are in phase, when the 
handling unit has performed the "Pick" operation, it has to wait a full 
cycle of the lift and carry device before performing the "Place" operation 
(instead of a half-cycle in the previous case). This results in the 
handling unit having to operate at a rate which is half that of the lift 
and carry device. As the transfer rate of the sub-assemblies has to be 
ensured, two consecutive transfer stations consequently have to be 
disposed operating in parallel, either by fitting two handling units or, 
more simply, a single handling unit equipped with two gripping heads. 
The machines which have just been described are limited to the transfer 
function, which is the essential function of a convergence station. Yet as 
the transfer proper only occupies a small longitudinal space, it is 
obvious that such a machine can, according to requirements, be completed 
for other operations of the process. On the main track, these operations 
can be located upline or downline from the transfer. On the branch track, 
they must be located upline. 
A limiting case of a convergence station can thus occur : that where the 
branch line is reduced to the branch track of the machine itself. There is 
then no branch machine upline, and recirculation of the empty palettes 
takes place directly between the upline and downline of the branch track. 
A machine of this kind will be simply called "double machine", and not 
convergence station. It is indicated when a sub-assembly has to be 
produced which requires few operations only, but the latter must be 
performed away from the main product.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 represents a manufacturing system comprising a main line 1 and a 
branch line 2 each comprising a certain number of standalone machines. The 
junction of these two lines occurs at the level of the convergence station 
3, on which both the main and branch lines can be seen, along with the 
cross-wise arrow representing the transfer of the sub-assembly coming from 
the branch line. 
The machine 4, incorporated in the main line, is a double machine, i.e. it 
comprises, in addition to its main track, a branch track on which a fairly 
simple component or sub-assembly is produced, which is transferred to the 
main track at the station marked by the cross-wise arrow. 
The machine 5 being at the end of the line, the cross-wise arrow represents 
removal of the finished product. 
The broken line circuits 6, 7 and 8 represent recirculation of the empty 
palettes, respectively, of the main line 1, the branch line 2, and between 
downline and upline of the double machine 4. 
FIG. 2 represents a convergence station 3, whose frame 50 is equipped with 
two walking beams 11 and 11', respectively, of the main track and of the 
adjacent branch track. For the sake of clarity of the drawing, they are 
limited to their moving parts, moving in the rectangular cycle, and 
operating in conjunction with the feed and removal conveyors 12, 13, 12', 
13'. The palettes 14 are picked up from the conveyors 12 and 12', and 
placed on the conveyors 13 and 13', after passing through a certain number 
of workstations. Among these, the station 15 is equipped with a transfer 
handling unit 16 arranged to pick the sub-assembly up from the branch line 
at the point 17', and place it on the main line at the point 17. The next 
station 18 can be usefully equipped with a control device to check that 
the sub-assembly has in fact been placed and correctly positioned. 
From the operating point of view, the palettes 14 move in the same 
direction on both tracks, and it has been seen that the two walking beams 
operate in opposite directions, which is highlighted by FIG. 2 
representing the walking beam 11 in the downline position, and the walking 
beam 11' in the upline position. From this point, a full cycle will run as 
follows : 
Carry phase on the branch track and return phase of the walking beam 11 on 
the main track. During this phase, the palettes 14 are available on this 
track for working operations. It is therefore at this moment that the 
handling unit 16 has to be present at the point 17 to place a 
sub-assembly. 
Vertical movement phase in the course of which the walking beam 11 moves 
from the down position to the up position, and the walking beam 11' from 
the up position to the down position. It is approximately during this 
phase that the handling unit 16 performs its return travel from the point 
17 to the point 17'. 
Carry phase on the main track and return phase on the branch track. 
Sub-assembly picked up by the handling unit at the point 17'. 
Vertical position inversion phase and transfer of the handling unit from 
the point 17, and return to the initial situation. 
During the cycle described above, it can be seen that the three devices 
(the two walking beams and the handling unit) have each performed a full 
cycle. They therefore have to be synchronized at the same rate. The 
assembly operates so long as the feed takes place normally, i.e. so long 
as arrival of the palettes at the upline stations 19, 19' is detected, 
both on the main track and on the branch track. As soon as no palettes are 
detected on one of these tracks, the assembly stops in a standby position 
enabling the corresponding walking beam to wait for a palette to arrive. 
FIG. 8 illustrates the operating mechanism of a walking beam device with a 
rule 11 performing a rectangular cycle. The rule 11 is securedly united to 
guide blocks 130, 130' sliding on parallel horizontal rods 131, 131', 
which form a rigid assembly with the blocks 132, 132', which are 
themselves guide blocks sliding on vertical rods 133, 133'. The rule 11 
therefore has two degrees of freedom in both the horizontal and vertical 
directions. The drive is provided by the motor 113 (possibly with a 
reducing-gear incorporated) and is achieved via the pulley 134, the 
notched belt 135, and the pulley 136 itself wedged onto the camshaft 137, 
supported by the bearings 138, 138'. The shaft 137 supports the helicoidal 
cam 139 which generates the horizontal movement and the flat cams 140, 
140' which generate the vertical movement (the cams 140, 140' have the 
same shape; they are only fitted double to provide correct support for the 
vertical movable assembly 131, 131', 132, 132'). The horizontal cam 139 
operates in conjunction with the roller 141 securedly united to the rule 
11. It should be noted that the height of this roller and its penetration 
into the throat of the cam 139 are sufficient to tolerate vertical 
movement without becoming disunited. The vertical cams 140, 140' operate 
in conjunction with the rollers 142, 142' securedly united to the blocks 
132, 132', the return being ensured by the weight of the moving assembly 
(which can be reinforced by springs if necessary). As far as the 
horizontal movement is concerned, the return is provided by the cam 
itself, which has a dual effect. The rule 11 is controlled by an identical 
mechanism driven by the same motor 113 or a synchronized motor, the 
movements being staggered to move the rules 11, 11' in opposition. 
In addition to the transfer handling unit 16, the machine can be equipped 
with other working modules, both on the main track and on the branch 
track. Depending on the production requirements, activation of these 
modules can be systematic or not. The same is the case for the transfer 
module, which can be rendered inactive, and for the whole of the branch 
line, if certain versions of the product to be manufactured do not 
comprise the sub-assembly produced on this line. 
FIG. 3 represents the second version of the convergence station, in which 
the two moving walking beam parts 21, 21' are driven with the same 
movement, and can therefore be mechanically united and driven by the same 
mechanism according to FIG. 8. As the palette feed and return phases are 
then synchronized, and the handling unit 27 can only perform an operation 
on one of the tracks during the return phase, the handling unit 27 
therefore has to work alternately performing a "Pick" operation on the 
branch track during one cycle, and a "Place" operation on the main track 
during the next cycle. Its operating rate is therefore half that of the 
walking beam, which explains the necessity of devoting two workstations 
25, 26 to the transfer function, and of having two grips operate in 
parallel, to pick two sub-assemblies up simultaneously from the points 
28', 29', and then place them at the points 28, 29. 
As far as the upline area of the machine is concerned, it can be noted that 
the palette loading stations 30, 30' on the feed conveyors 22, 22' have 
been staggered one step. If this was not done, when restarting after an 
interruption, the first two palettes would reach the points 28, 28' at the 
same time, which would enable the sub-assembly to be transferred to be 
picked up at 28', but would not enable it to be placed at 28. In fact, as 
placing takes place at the next cycle, the palette involved would no 
longer be at 28, but at 29, and would therefore not receive a 
sub-assembly. The above-mentioned staggering enables this drawback to be 
overcome, by presenting the first palette of the main track at 28 one 
cycle later than the first palette of the branch track is presented at 
28'. The same precaution also enables the version changes of the 
manufactured product involving both tracks to be controlled correctly. 
In a slightly different solution, the stagger can be achieved by leaving 
the two walking beams the same, and using a retractable stop fitted on the 
feed conveyor 22, one step upline from the pick-up station of the palettes 
by the walking beam 21. 
FIG. 4 illustrates the kinematic operation of the machine described by FIG. 
3. The top diagram relates to the walking beam, and positions the 4 phases 
of the latter in time : carry (A), downward movement (D), return (R) and 
upward movement (M). The bottom diagram relates to the handling unit 27, 
which presents the horizontal movement phases : transfer (T) and return 
(R) between which the active "Pick" and "Place" operations take place. As 
these operations have to take place during the R phases of the walking 
beam, it is clear that the handling unit cycle (C2) has to be twice that 
of the walking beam (C1). 
In FIG. 5, still relating to the same type of machine, 6 successive 
situations are presented which occur when the machine starts up empty, 
separated chronologically by intervals corresponding to a cycle C1. 
Diagram a : the simultaneous presence of palettes is detected at the input 
of the main and branch tracks. A palette is represented by a blank disk ; 
the sub-assembly to be transferred is represented by a smaller black disk. 
The configuration in the diagram is that of FIG. 3 : input stations 30, 
30', and transfer stations 28, 29, 28', 29' administered by the 
double-grip handling unit 27. 
Diagram b : progression one step. 
Diagram c : new progression one step. 
The handling unit picks a sub-assembly up from 28'. 
Diagram d : the handling unit has moved over to the main track. It places 
the sub-assembly it had picked up from 28' on the station 28, where the 
first palette of the main track is located at this moment. 
Diagram e : the handling unit has returned to the branch track. This time 
it picks up two sub-assemblies from the stations 28', 29'. 
Diagram f : the handling unit is again on the main track where it places 
the two sub-assemblies at 28, 29, where the second and third palettes of 
the main track are located, etc. 
This process makes the palette transfer system, and the role played by the 
stagger on input clearly apparent. 
A similar scenario could be built up assuming that it is not a start-up 
that is involved, but a change in the version of the manufactured product. 
The problem is then to prevent a "hybrid" product from being manufactured 
incorporating a sub-assembly of a version A in a basic product of a 
version B. If it is assumed that the palettes represented in FIG. 5 belong 
to the version B, and that they were preceded by palettes of the version 
A, it can be seen that this type of mixing will not occur, provided that 
there is an agreement between the number of palettes per version on the 
main and branch tracks. If this is not the case, there will at one stage 
be a disagreement between the versions presented at the input stations 30, 
30', a situation which absolutely must be detected by suitable scanning 
means, and which must be corrected by removing the surplus, which may 
occur either on the main track or on the branch track. This removal can be 
performed manually, or, to remain within the spirit of the invention, 
automatically. If the surplus occurs on the main track, a mechanical 
removal device of the palettes concerned has to be installed. This device 
can be placed at any point of the machine, preferably at the output, where 
it can then also perform the function of removing the palettes rejected 
for quality reasons, should the machine also comprise one or more checking 
stations. If the surplus occurs on the branch track, it is also possible 
to proceed by removal of the palettes concerned, but also, more simply, by 
fitting a retractable shoot at the placing points 28 or 29, enabling the 
sub-assemblies picked up by the handling unit 27 to be collected and 
removed, this shoot being automatically presented when a surplus occurs 
and retracted during normal working. 
This type of problem naturally only arises if the change of version 
involves both the main and branch lines. 
FIG. 6 represents an embodiment of a double machine which, as has been 
seen, is a limited case where the branch line is limited to the branch 
track of the convergence station itself, without any other machine upline. 
The problem specific to this type of machine is to organize the 
recirculation of the empty palettes between downline and upline of the 
machine. This recirculation should preferably take place without 
encroaching on the space taken up by the working modules and their access, 
which makes the simple solution consisting of a single horizontal loop 
practically impossible. 
In FIG. 6, the walking beams 31, 31', respectively, of the main track and 
of the branch track, and the upline and downline conveyors 32, 32', 33, 
33' can be seen. On the main line, these conveyors are relayed by the 
conventional conveyors 34 and 35 which belong to the inter-machine transit 
system. On the branch line, recirculation of the palettes is accomplished 
by passing under the main track, access to this lower level being achieved 
for example, by a simple slide 36, the palettes then being taken over by a 
scale-type conveyor 37 which takes them back upline of the machine, then 
takes them up to the working surface level to present them upline from the 
conveyor 32'. In a system of this kind, the quantity of palettes to be put 
into use must be sufficient to occupy all the workstations of the branch 
track, plus a small additional quantity calculated so that there is never 
any wait for a palette at the branch track input. As these palettes return 
empty, and therefore in a standardized state, there is no problem of 
agreement at the machine input, and therefore no need for staggering 
between the two tracks. 
As on a conventional convergence station, a transfer handling unit 38 is 
fitted, generally towards the downline side, to transfer the part or 
sub-assembly produced on the branch track to the main track. In FIG. 6, 
this involves a machine with a walking beam in phase, and therefore 
equipped with a double-grip handling unit, but this machine could just as 
well be imagined with a walking beam in opposition, in which case it would 
be equipped with a single-grip handling unit. 
FIG. 7 illustrates another alternative embodiment of palette recirculation 
presented according to an elevational view of the branch track. In this 
alternative embodiment, the palettes 42 are articulated to one another so 
as to constitute an endless chain 43. The articulations of this chain must 
have the required precision, but also a certain freedom to allow the 
normal lift and carry clearance by the walking beam 41'. Upline and 
downline, the palettes are guided by appropriately shaped slides 44 and 45 
which ensure the transition between the active area and the return area. 
To limit friction, these slides can be replaced by roller ramps.