Transfer device on a press

Abstract

The present invention relates to a device on a press and to a method for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of the press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. The conveying means are here moved in the longitudinal direction by means of an external drive unit which is merely synchronized with the movement of the press. The motor-powered external drive unit is mechanically coupled to the conveying means in such a way that the conveying means can be moved back and forth without reversing the rotation of the external drive unit.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a device on a press and to a method for incrementally conveying workpieces in a longitudinal direction from a receiving station through at least one tooling station of the press with the aid of conveying means for the workpieces, which conveying means are moved back and forth in cycles and in synchrony with the movement of the press in the longitudinal direction, as well as in a transverse direction substantially perpendicular thereto in order to grip or release the workpieces. The conveying means are moved in the longitudinal direction by means of an external drive unit, which is merely synchronized with the movement of the press. Transfer devices are characterized, relative to so-called follow-on composite tools, in that the part to be formed in the press, in the region of the receiving station, is firstly separated, for example from a continuous strip, for example by cutting-off or punching, and is then conveyed,...

AI Technical Summary

Benefits of technology

[0012] This object is achieved in that the motor-powered external drive unit is mechanically coupled to the conveying means in such a way that the conveying means can be moved back and forth without reversing the rotation of the external drive unit.

[0013] Typically, if external drive units are used, especially in the case of servo motors, a fundamental problem consists in the fact that the achievable accelerations and stroke rates, respectively, are limited due to the forward and return movement which has to be induced. Indeed, this back and forth movement calls for a rapid deceleration and acceleration, respectively, of the servo motor (stop and go), and since typically, in a device of this type, large moved masses are present, then the possible accelerations are thus limited in comparison to purely mechanical solutions. One heart of the invention thus consists in providing a mechanical coupling of the motor-powered external drive unit to the conveying means, which coupling allows the external drive unit to be operated without reversing the rotation and thus allows the otherwise necessary accelerations to be avoided, reduced or placed into sections where few masses are accelerated. The actual reversing rotation is here produced by an appropriate mechanical gear, which converts the back and forth movement, while the external drive unit, typically a servo motor, can be operated, for example, at a rotation speed which is constant in the feed operation and with constant direction of rotation. This design yields a large number of unexpected advantages, the advantages of a purely mechanical drive essentially being able to be combined with those of a pure external drive unit.

[0016] A particularly preferred embodiment of the present invention boasts means which allow the motor-powered external drive unit to be operated at different speeds in dependence on the feed cycle. This inherent flexibility of the external drive unit allows, inter alia, the feed angle to be changed, and hence taller structural parts to be formed in the press, without the need for mechanical conversions. In particular, the speed of the longitudinal movement of the conveying means thus becomes variable within certain limits, without mechanical alterations, purely by controlling the speed of the external drive unit; this specifically without reversing the direction of rotation of the servo motor as is necessary in the prior art, i.e. in the case of high cycle rates.

[0021] A first preferred mode of operation is here characterized in that the motor-powered external drive unit is run at constant rotation speed and with constant direction of rotation. Typically, the cam characteristic of the gear is optimized for a constant operation of this type. Alternatively and particularly preferably, it is now possible, however, to operate a device as has been described above such that the motor-powered external drive unit is operated in dependence on the feed cycle at varying rotation speed yet with preferably constant direction of rotation. Thus, the flexibility of an external drive unit in the longitudinal direction is able to be combined with the high stroke rates of a purely mechanical transport in the longitudinal direction. Particularly preferably, the rotation speed of the external drive unit proceeds to be varied in those sections of the feed cycle in which the conveying means perform no longitudinal movement (so-called dwell sections). In the other sections, i.e. in the feed operation and in the return stroke, the rotation speed of the external drive unit is preferably kept constant, an increased, constant rotation speed preferably being operated, for example, in the feed operation. In those sections of the feed cycle in which the conveying means perform no longitudinal movement, the rotation speed is preferably initially slowed and then accelerated to the value which is relevant to the next section of the cycle. Thus, if optimal use is made of the cam characteristic of the gear (for example designed for constant speed of the external drive unit) with respect to running behavior at constant rotation speed of the external drive unit, the feed angle is able to be reduced. The variation of the rotation speed of the external drive unit in the dwell sections has the advantage, in particular, that practically no moved masses (apart from the shaft of the servo motor and of the worm gear and, where appropriate, a reduction gear) are present there and energy losses (deceleration) and high energy consumption (acceleration), respectively, can consequently be prevented. In this way, stroke rates of more than 200 strokes / min or more than 270 strokes / min, for example, can be achieved. Stroke rates in the region of or more than 300 strokes / min, or even in excess of 350 strokes / min, are typically possible.

Problems solved by technology

Typically, if external drive units are used, especially in the case of servo motors, a fundamental problem consists in the fact that the achievable accelerations and stroke rates, respectively, are limited due to the forward and return movement which has to be induced.

Indeed, this back and forth movement calls for a rapid deceleration and acceleration, respectively, of the servo motor (stop and go), and since typically, in a device of this type, large moved masses are present, then the possible accelerations are thus limited in comparison to purely mechanical solutions.

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