Folding press with deflection compensating means

The upper and lower frames of a folding press include a deflector capable of producing a deflection of at least one portion of a press member. A comparison device is provided which includes two longitudinal bars arranged, respectively, in longitudinal housings of each of the upper and lower frames. One of the ends of each of the bars is secured to its respective housing, the other end of each of the bars being free to move longitudinally in the housings and being connected to a measuring device respectively fixed to each of the upper and lower frames, so as to measure the respective movements of the other ends of the bars in their respective housings in response to any deflection of the upper and lower frames. The comparison device is arranged for controlling the deflector to compensate for any difference in deflection of the frames.

FIELD OF THE INVENTION 
The invention relates to a folding press comprising an upper frame and a 
lower frame, at least one of the frames comprising at least one deflection 
means of at least one portion of at least one press member to remedy the 
deficiencies inherent to the folding process. 
BACKGROUND OF THE INVENTION 
During the folding with a folding press, deflections occur inside the two 
frames, these deflections being the more important as the dimensions of 
the press are important. These deflections depend, in particular, on the 
shape, the dimensions and the quality of the material to fold, and they 
are generally not identic for both frames. In particular, when folding a 
piece, the upper frame has a tendency to bend upwards under the effect of 
the thrust of the working cylinder pistons, generally arranged at each of 
the ends of the press, leading to a longitudinal upwards deflection of the 
surface of the upper die holder. Similarly, the lower frame has a tendency 
to bend downwards leading to a downwards longitudinal deflection of the 
surface of the lower die holder. As a result, the respective working 
surfaces of the two frames and, therefore, of the dies are no longer 
parallel. The depth of penetration of the male die into the female die 
will then no longer be the same over the whole length of the press. It 
follows that the folding angle obtained is not the same over the whole 
length of the piece which is folded. 
In order to remedy these difficulties, certain folding presses comprise 
compensation cylinders placed in one or both of the frames and arranged to 
compensate for the deflections due to the working of the press and to 
obtain, in particular, similar deflections of the upper and lower frames. 
However, these systems require a great number of trials for adjustment and 
most of them require the user to determine in advance the deflection due 
to the operation of the press. 
SUMMARY OF THE INVENTION 
The object of the invention is to remedy the above inconvenience by 
proposing a folding press in which the depth of penetration of the male 
die into the female die remains constant over the whole folding length 
without requiring a preliminary adjustment of the press. 
To this effect, the invention relates to a folding press comprising an 
upper and a lower frame, at least one of the frames comprising at least 
one means for deflecting at least a portion of at least one member of the 
press to remedy to the deficiency inherent to the folding process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The folding press shown in FIG. 1 comprises an upper frame 1 supporting a 
male die and a lower frame 2 supporting a female die. The lower frame 
comprises a plurality of compensation cylinders 3 used to compensate the 
deflections inherent to the folding process. The action of this 
compensation cylinders is controlled by an electronic device 11, such as a 
numerical control device. The comparison device for the deflection of each 
of the frames comprises longitudinal measuring means 4, 5 used to measure 
the elongation of said frames under deflection, said means being connected 
to the numerical control device 11. 
According to an embodiment of the comparison device shown in FIG. 2, each 
of the frames comprises two longitudinal bars 4, 5 arranged, respectively, 
in housings 6, 7 provided, respectively, in the upper frame and in the 
lower frame. The upper bar 4 is merely placed in the housing 6. It is 
secured to the upper frame by a fixing means 14 attached to one of its 
ends. When any deflection of the upper frame occurs, the other end of the 
bar, which is free, can thus move freely with respect to the housing 6. 
This other end of the bar is fixed to a measuring means 9, such as for 
example a linear inductive sensor mounted on the upper frame at the end of 
the housing 6. Similarly, the lower bar 5 is merely placed in the housing 
7. One of its ends is fixed to the lower frame by a fixing means 15. A 
second measuring means 10, similar to the measuring means 9, is mounted on 
the lower frame at the end of the housing 7 and is connected to the second 
end of bar 5. 
Both sensors 9 and 10 are connected to the numerical control device 11 
which is, in particular, adapted to receive the signals delivered by each 
of the sensors 9 and 10 upon any deflection of the upper and lower frames, 
for receiving said signals and for controlling automatically the operation 
of the compensation cylinders 3 until, at the output of sensor 10, signals 
are obtained which are equal to those obtained at the output of sensor 9. 
At this moment, as shown in FIG. 2 by dotted dashed lines, the surfaces of 
the two die holders of the upper and lower frames are parallel. The depth 
of penetration of the male die into the female die will then be constant 
over the whole folding length. 
As shown in FIG. 3, the upper bar 4 can be lodged in the lower part of the 
upper frame in a housing 6 provided at the surface of one of its faces. 
This housing can, of course, be provided at any other place of the upper 
frame or of the upper die holder. 
The lower bar 5 shown in FIG. 4 is arranged in a housing 7 provided in the 
lower part of the table 8 of the lower frame. This housing can, of course, 
also be provided at any other place of the lower frame.