Metal working – Plural diverse manufacturing apparatus including means for... – Including composite tool
Patent
1994-01-14
1995-02-07
Briggs, William
Metal working
Plural diverse manufacturing apparatus including means for...
Including composite tool
72452, 83602, 140105, B23P 2300, B21F 100
Patent
active
053866207
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is based on a machine tool with the features given in the preamble to claim 1.
STATE OF THE ART
Such a machine is known from DE-PS 35 44 087. In the known machine, the tools are driven by a cam gear which has two driven cam plates located on the same axis. A freely rotating roller is in contact with the circumferential area, designed as the cam track, of each of the two cam plates. Each of the two rollers is supported at the end of a two-arm lever which transmits the deflection of the roller caused by the rotating cam track to a tool half, or to a holder for it, which is located at the opposite end of the lever. The two levers are connected together by a tie-rod on whose ends the two levers are pivotably supported.
So that the rollers remain continuously in contact with the cam plates, they are pressed or pulled by frictional connection onto the cam track formed by the circumferential surface of the cam plate; this is generally effected by springs. The preload forces applied by the springs must be larger than the forces arising during the acceleration and braking of the tools in order to ensure that the rollers do not lift from the cam plates. A disadvantage of these preloading forces, on the other hand, is that they make the drive more difficult because they have to be overcome when the tools are driven so that a correspondingly strong and heavy driving motor is required. Another disadvantage arises from the fact that the torque to be provided by the driving motor for the actual operating process carried out by the tools is increased by the torque which is required to overcome the preloading forces acting on the rollers; in consequence, the response threshold of an overload clutch provided in the drive train to protect the tools from damage in the case of overload has to be increased in an undesirable manner. Another disadvantage consists in the fact that a device for preloading the rollers by springs prevents a displacement of the lever, desirable per se, parallel to the driving shaft of the cam plate; such a displacement capability is desirable to adapt the machine tool for different operational tasks.
In order to avoid the preloading forces, it is known art to guide the roller in a groove on the cam plate (grooved cam gear) or to guide a pair of rollers on both sides of a bead on the cam plate (beaded cam gear) instead of on the circumferential surface of the cam. For the same follower motions as those of a cam gear in which the roller runs externally on the circumferential surface of the cam plate, however, grooved cam plates and beaded cam plates have a larger diameter so that larger inertia torques appear in the cam gear. This is undesirable because the machine can only be stopped more slowly or the driving forces and braking forces become larger and wear increases. The acceleration and braking forces of the tool halves and the clamping devices carrying them generally appear in the direction of the tool motion. They are particularly disadvantageous in the case of a rapid reversal of acceleration because the inertia forces due to the tools and gear elements appearing in the direction of the tool motion excite the machine frame and the work-piece holder to vibrations, in some cases at a high excitation frequency. In order to counter the excitation of vibration, it is known art to displace the apex of the reversal of acceleration in the direction of the starting acceleration so that the braking deceleration is reduced--but with the disadvantage that the starting acceleration is increased.
In DE-PS 35 44 087, there is, furthermore, an indication that the return of the tools can be controlled by cams or cam plates but without positive information on how this has to be done and whether it has an influence on the vibration behaviour.
The disadvantages mentioned are particularly serious in the case of machines for punching and shaping the lead-outs of integrated circuits because this work must, on the one hand, be carried out with great accuracy, particularly in the
REFERENCES:
patent: 3886829 (1975-06-01), Criblez
patent: 4371012 (1983-02-01), Weresch
patent: 4497196 (1985-02-01), Bakermans et al.
patent: 4845833 (1989-07-01), Weresch
Gabel Ulrich H.
Hinterlechner Gerhard
AATEC Assembling Automations Technik GmbH
Briggs William
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