Conveyors: power-driven – Conveyor section – Load simultaneously engaged between and moved by a plurality...
Reexamination Certificate
1999-09-13
2001-05-22
Valenza, Joseph E. (Department: 3651)
Conveyors: power-driven
Conveyor section
Load simultaneously engaged between and moved by a plurality...
C072S405130, C072S405160
Reexamination Certificate
active
06234302
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of 198 41 621.0, filed Sep. 11, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a transfer system having a failure protection system.
Typical known transfer systems are, for example, three-axis transfer systems, feeding or removing devices. For example, DE 33 29 900 C2 discloses a three-axis transfer system having two parallel transfer rails spaced from one another. These are arranged along the parts-transporting direction such that, between one another, they enclose the individual working stations defined by press tools. The transfer bars carry out a transfer movement which contains a lifting and lowering component as well as a transporting component directed in the longitudinal direction of the transfer bars. In addition, for receiving workpieces and for depositing workpieces, the transfer bars are moved laterally toward and away from one another. Electric drives are used for moving the transfer bars.
For receiving workpieces, the transfer bars are laterally adjusted such that corresponding gripper and receiving devices engage with and receive the workpieces. For this purpose the transfer bars must be moved laterally into the open tool. After the depositing of the workpieces in the respective next following open tool, the transfer bars must be moved laterally out of the tool, before this tool closes again.
For the lateral opening or closing movement of the transfer bars, a narrowly defined time window must be observed. If the bars are late during the opening, a collision may occur between the closing tool and the transfer bars or their gripper or receiving devices. This results in extensive damage.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a transfer system which moves its transfer devices with an increased safety within defined time windows.
This object has been achieved by providing a transfer system having a transfer device, which is linked with at least one working station, having at least two driving devices which are both assigned to the transfer device, and having a coupling device, by means of which the driving devices are connected with one another and which, in a selected relative movement or operating range, has a power or torque transmission which is lower in its amount than a limit value, and which otherwise has a higher power or torque transmission.
The transfer system according to the present invention has a mechanical transfer device which supplies workpieces to at least one working station and removes workpieces from this working stations and in linked to this working station in this sense. The transfer device is driven by several, at least two driving device which are coordinated with one another and preferably operate synchronously. The driving devices are connected by a coupling device which has a selected working range in which the work transmission or torque transmission is low or zero. This working range is a passive range in which a mutual influencing of the drives is low or impossible. When there is a departure from this working range, the coupling device transmits so much force or torque between the driving devices that the movement of the transfer device is carried out in the defined time window, and a collision between the transfer devices and devices of the work station is avoided.
The coupling device permits independent operation of the driving devices so that there can be no disturbances or interferences between the two driving devices if these are operated properly. If one driving device does not operate properly, however, there will be a departure or leaving from the passive range of the coupling device. As a result, the remaining, properly operating driving device is permitted to carry out the function of the driving device which is no longer operating properly. If, for example, one driving device fails, the concerned drive will no longer be stopped but is pulled along by way of the coupling device by the properly operating driving device, at least first until moving out of the collision range.
In a transfer press, the transfer devices are preferably formed by two transfer bars which are arranged parallel to one another and extend along a transporting direction. The transfer bars preferably span several working stations and cause the workpiece transport from one station to the next. For receiving workpieces, the transfer bars are moved toward one another and for the release, carry out a movement away from one another. These movements are caused by the two driving devices. One driving device is assigned to one transfer bar and the other driving device is assigned to the other transfer bar. The coupling device passively couples these two driving devices with one another. That is, in normal operation, no power transmission takes place by way of the coupling device. Additional driving device pairs of this type may be arranged along the longitudinal direction of the transfer bars. Each pair of driving devices contains two driving devices respectively which are coupled with one another. As required, however, other driving devices may also be coupled with one another by corresponding coupling devices. The advantage of the coupling of transfer systems which are arranged side-by-side and which are each assigned to different transfer bars is the close spatial proximity so that only a short spatial distance must be bridged by the coupling device and corresponding transmission devices.
The coupling device is preferably a mechanical coupling device, such as a rotating coupling device or a translational coupling device. The coupling device has an operating range with a low torque transmission or power transmission. This may be a play range which, in a rotating coupling, is a rotating play. In a translational coupling, the play range is a translational play. In this play range, the power transmission or torque transmission may be low. In any case, it falls below a limit value which is such that the properly operating drives are virtually unconnected with one another. This permits arrangement of the driving devices in mutually independently operating control loops which each separately set a uniformly defined desired value which can change with respect to time. Control oscillations or control deviations also of a temporary nature do not lead to a disturbance between the driving devices. This is particularly true when the selected working or play range is at least as large as the sum of the amounts of the temporary control deviations to be maximally expected in the case of both drives.
Outside this operating range, a considerable torque transmission takes place which is at least so large that, in the range of the failed or no longer fully operable drive, the transfer device is moved properly, i.e., within a time-related tolerance field, out of a danger zone defined by the working station.
In the ideal case, the characteristic curve of the coupling device is therefore a bent characteristic curve which has no torque transmission or power transmission for rotating angle or path differences between the two drives which fall below a limit value. In this situation, the characteristic curve is axially in parallel to an angle axis or path axis in a torque(power)-angle (path) diagram. Outside this operating range, an increase of the angle difference or path difference is ideally no longer permitted. In this case, the characteristic curve is in parallel to the torque (power) axis in the above-mentioned diagram. As an alternative, the coupling device may have a certain flexibility in order to configure the coupling engagement not to be excessively hard.
Instead of the rotating angle difference or path difference, a differential rotational speed or a differential moving speed can also be used as a criterion for engagement and disengagement of the coupling device. Furthermore, spring or damping devices can be arranged on the coupling device. In addition to moving the transfer rails and the gripper devices out of t
Greiner Martin
Rieger Walter
Thudium Karl
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Schuler Pressen GmbH & Co. KG
Valenza Joseph E.
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