1. Field of the Invention
The present invention relates to machines for forming metal parts, such as by bending, punching and/or swaging the parts, and, more particularly, is concerned with an electromechanical drive for a hydraulically translating drive system of such metal part forming machines.
2. Description of the Prior Art
Machines for forming metal parts are known which have a vertically disposed workbench on which tools which operate sequentially or in parallel are disposed on a sliding carriage so as to be movable therewith. The tools can be operated to bend metal parts appropriately introduced at several sites in different planes as well as at different angles.
To slidably move each sliding carriage and tool therewith, a hydraulic translating driving system is provided in the machine which includes a hydraulic cylinder-like transmitter and a hydraulic cylinder slidably moving the sliding carriage. The hydraulic transmitter and the hydraulic cylinder are connected in a closed circuit via a line conveying hydraulic fluid between them. The hydraulic cylinder includes a cylinder housing and a working piston therein which slides the carriage and the tool therewith. The hydraulic transmitter also includes a piston which, for purposes of generating pressure, is slidable via a cam disk seated on a common driving shaft of the machine on which other cam disks are disposed for driving other systems of the machine operating in parallel. The driving shaft is driven via a common electric drive, for example a stepping motor, of the machine.
In order to reset the working piston of the hydraulic cylinder from its operating position, it is connected with a pressure storage system, for example a pressure line system, which functions against a nitrogen bladder in a container for pressure storage. If the corresponding hydraulic transmitter is set to be pressureless, the working piston of the pressurized hydraulic cylinder is moved back again via the pressure storage medium and therein takes back the carriage and the bending tool on the workbench therewith.
In machines of this type only small quantities of oil or hydraulic fluid are moved in their working systems operating separately from one another. For that reason, high operating speeds can be attained.
However, a disadvantage which has been found in such machines is the relatively high imprecision of the cam disk control which, due to the hydraulic translation, exerts a strong effect on the precision of the working steps of the tools. For increasing the precision of the operating steps of such machines with several tools on one workbench, it is known to use so-called linear amplifiers operating as individual drives, in which an NC valve is combined with the hydraulic cylinder in one structural unit. However, in such machines no hydraulic translation takes place. The hydraulic pressure is provided via a central hydraulic supply which under electronic control supplies jointly several such linear amplifiers. The linear amplifiers operate with stepping motors and ball spindles via which the working cylinder can be moved into its starting working position or be retracted from it. In such working position the pressure is applied onto the working position under control via the central hydraulic supply. Such devices have the disadvantage that via the central hydraulic supply relatively large quantities of oil must be transported which, by necessity, leads to a slowing of the operating speed. Linear amplifiers for the described application purpose are known from the publication HUBER, H.-J.: Flexible Automatisierung, nit digital gesteuerten electrohydraulischen Servoantrieben, in: VDI-Z, Spezial Apr. 1, 1991 Antriebstechnik, pp. 92, 97-98.
Consequently, a need exists for an innovation which will overcome the aforementioned disadvantages without introducing other disadvantages in place thereof.
The present invention overcomes the aforementioned disadvantages by providing an electromechanical drive for a metal part forming machine. The electromechanical drive increases the mechanical control and working precision of a hydraulically translating drive system of the metal part forming machine with the additional capability of increasing the operating speed of the machine.
Accordingly, the present invention is directed to an electromechanical drive for a metal part forming machine. The electromechanical drive includes a source of rotary drive motion such as an electric motor having a rotary output shaft, a drive shaft attached to the rotary output shaft and adapted to undergo rotational motion therewith about a rotational axis defined by the drive shaft, and a motion conversion mechanism coupled with the drive shaft and being movable between expanded and retracted positions along the drive shaft in response to the rotational movement of the drive shaft. The motion conversion mechanism has a first coupling element stationarily disposed at a fixed location offset from one side of the drive shaft and a second coupling element movably disposed at another location offset from another side of the drive shaft angularly displaced from the one side thereof for connecting with an external mechanism such that movement of the motion conversion mechanism between the expanded and retracted positions along the drive shaft in response to rotation of the drive shaft about the rotational axis causes movement of the second coupling element toward and away from the another side of the drive shaft and thus movement of the remainder of the motion conversion mechanism except for the fixed first coupling element, and movement of the source of rotary drive motion, the drive shaft and the external mechanism connected to the second coupling element therewith along a generally linear reciprocatory path extending in a generally orthogonal relationship to the rotational axis of the drive shaft.
These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention.