Driving mechanism for tool slides of punching and bending machines

In a punching and bending machine the driving mechanism 10 for a reciprocating a tool slide 50 comprises a pair of cam plate and push rod arrangements 20, 38 and 22, 58 one for the working stroke and the other for the return stroke. They move in an oil filling contained in a hermetically sealed housing 28. The contacting ends of the push rods 38, 58 are provided with carbide tippings 46, 60 and the peripheral surfaces of the cam plates 20, 22 are hardened or nickel-plated. The driving mechanism can be used in high speed machines making at least 2000 strokes per minute.

The present invention relates to a driving mechanism for tool slides of 
automatic punching and bending machines comprising a frame, a shaft 
rotatably supported on the frame, a driving pinion fixed on one end of the 
shaft, for engagement with a central wheel of a bending unit, a cam plate 
fixed on the opposite end of the shaft, connecting means contacting the 
circumference of the cam plate and connected with a tool slide for a 
reciprocating motion. 
According to the state of art the connecting means consists of a small idle 
pully rotatably supported on a shaft fixed on the tool slide. Such driving 
mechanisms have been used in the past in large numbers and operate 
satisfactory in slow-speed punching and bending machines. However when the 
operating speed is increased wear at the idlepully will occur already 
after a short time. The result is that the punching and bending operations 
not longer can be precisely performed and when handling precise work 
pieces waste will be produced. 
Therefore one object of the invention is to improve the driving mechanism 
of the afore mentioned type so that it can be used in connection with 
high-speed punching and bending machines. One further object is to provide 
a new driving mechanism which allows a higher stroke number per minute 
without any troubles and for a long lifetime. Last not least it is an 
object of the invention to provide for a driving mechanism which can 
co-operate even with cam plates having narrow concave circumferential 
portions. 
According to the invention in the driving mechanism as described above the 
connecting means is formed as a push rod provided with a convex end face 
as seen in axial direction of the shaft the convex endface being provided 
with a carbide tipping, the driving mechanism further comprises a housing 
fastened at the frame, the housing being hermetically sealed and filled 
with oil, the cam plate being arranged within the housing, a wall of the 
housing provided with a bore, sealing means within the bore, and the push 
rod extending through the bore into the housing. 
The invention gains the advantage that the punching and bending machine can 
be operated with a much higher speed up to 2000 strokes per minute and 
even more, avoiding any wear or troubles during a long operating time. The 
oil filling provides for a continuous oil film between the cam plate and 
the push rod avoiding any seizures. In contrast to the state of art 
between the cam plate and the push rod no rolling motion but a pure 
sliding motion takes place. Nevertheless due to the oil film between the 
sliding parts any wear can be avoided which is in contrast to known 
constructions using idle pullies on the tool slides. This surprising 
effect can be explained by that the idle pullies must have a relatively 
small diameter because there are cam plates having concave circumferential 
portions into which the pullies must fit. The pullies therefore are 
rotated with a much higher speed than the cam plates. Further because of 
the shapes of the cam plates alternating accelerations and decelerations 
occur which are responsible for sliding and grinding motions instead of 
pure rolling motions between the cam plate and the idle pully. Because of 
this dry sliding friction the known driving mechanism would have only a 
short life time when operated with high-speed machines. 
The present invention avoids these disadvantages. 
Further embodiments of the invention consist in that the running surface of 
the cam plate is nickel-plated or carbide-plated, and in that an 
additional cam plate push rod arrangement for the return motion of the 
tool slide is provided in the housing, the cam plate of which being 
fastened on the shaft and the pair of push rods being 180 degrees offset 
to one another with respect to the driving shaft, and in that the push rod 
for the return motion is adjustably fastened on a tie rod which is 
parallel with the push rod having the carbide tipping and sealingly 
protrudes through the same wall of the housing, the push rod and the tie 
rod being fixed at a common part of the tool slide. 
The invention avoids any return springs because the tool slide return 
motion is positively controlled by the return stroke cam plate and push 
rod arrangement. Both of that cam plate and push rod arrangements are 
provided within the hermetically sealed housing containing the oil 
filling. Due to that the machine can be operated with high speeds in the 
region of 2000 revolutions per minute.

The drawings show a driving mechanism 10 which has a frame plate 12 in 
which a bearing 14 for a shaft 16 is provided. A pinion 18 is fastened on 
one end of the shaft 16 and a first cam plate 20 and spaced therefrom a 
second cam plate 22 are fastened on the opposite side of the shaft. The 
shaft 16 has a conical portion 24 on which a fastening body 26 is clamped 
in such a manner that the first cam plate 20 can be continuously adjusted 
in relation to the second cam plate in peripheral direction. 
A hermetically sealed housing 28 is fastened at the frame 12 and is 
composed of side walls 30, a back wall 32, a front wall 34, and an upper 
wall 36 opposed to the frame 12. The hermetically closed housing 28 
contains an oil filling. 
The front wall 34 of the housing 28 has a pair of bores in each of which a 
push rod 38 and a slide member 40 are supported respectively for 
reciprocating motions. Push rod and sliding member are sealed against the 
housing by sealing rings 42, 44. The push rod 38 has a cylindrical convex 
peripheral face on the front side of which, i.e. in the axial 
cross-section of FIG. 1 containing the axis of the shaft 16; the 
peripheral face of the front end forms a straight line while in the radial 
cross-section of FIG. 2 this peripheral face is convexedly curved. The 
push rod is provided with a carbide tipping 46 at its front end peripheral 
face. The push rod 38 is held in contact with the circumference of the cam 
plate 20 by means of a return motion arrangement which will be described 
later. Linear contact exists between cam plate 20 and push rod 38. 
The push rod 38 and the slide member 40, both of equal cross-section, are 
connected with one another by a connecting member 48 outside of the 
housing 28. The connecting member 48 is adjustably connected with a tool 
slide 50 carrying the bending tool (not shown). 
The slide member 40 passing through the packing ring 44 and the front wall 
34 is connected with a tie rod 52 which is linearly movable in opposite 
directions and guided for this reciprocating motion in a strut 54 of the 
housing. A bolt 56 extending rectangularly to the tie rod is fastened at 
the tie rod and can be adjusted in the longitudinal direction of which. A 
push rod 58 in form of a projection of the bolt has a carbide tipping 60 
as the first push rod 38 and its front end is of cylindrical convex shape 
as the front end of the first push rod 38. The push rod projection 58 is 
in contact with the second cam plate 22. The contact lines between cam 
plate 20 and push rod 38 in one case and between cam plate 22 and push rod 
projection 58 in the other case are oppositely situated, i.e. they are 
situated in the cross-section plane of FIG. 1 containing the axis of the 
shaft 16. 
In the position of FIG. 2 the cam plate 20 and the push rod 38 have 
displaced the tool slide 50 into the end position of which. When the 
rotation of the shaft 16 is continued the push rod projection 58 runs on a 
peripheral portion of increasing diameter of the cam plate 22 and draws 
back the tool slide into the opposite end position of which by means of 
the tie rod 52, the slide member 40, and the connecting member 48. Due to 
the fact that both of the cam plate push rod arrangements 20, 38 and 22, 
58 run in the oil filling a high speed drive is possible without troubles. 
The peripheral surfaces of the cam plates 20, 22 are hardened or are 
nickel-plated or carbide-plated in order to provide for a long life-time.