TECHNICAL FIELD

The present invention relates to a workpiece holding device for holding a workpiece by a plurality of holding claws.

BACKGROUND ART

Conventionally, in order to improve production efficiency, at least a part of each process in a production line has been automated and a robot carries out certain work. In this case, for example, as described in Japanese Laid-Open Patent Publication No. 2013-000857, a workpiece gripping device (what is called a robot hand) is attached to a robot for taking a workpiece out of a predetermined place, and transporting the workpiece to another place.

SUMMARY OF INVENTION

Conventional workpiece gripping devices are capable of gripping workpieces having simple shapes such as a member in the form of a flat plate. However, it has not been possible for such workpiece gripping devices to grip workpieces with various shapes. For example, the workpiece gripping device according to Japanese Laid-Open Patent Publication No. 2013-000857 can grip workpieces with various sizes, but cannot grip workpieces with various shapes.

A main object of the present invention is to provide a workpiece holding device that can hold workpieces with various shapes or in various orientations.

According to one embodiment of the present invention, the present invention provides a workpiece holding device including a plurality of holding claws configured to hold a workpiece. The workpiece holding device includes a plurality of claw opening/closing members provided for the holding claws, respectively, and configured to displace the holding claws in a direction closer to or away from the workpiece, a holding member configured to hold each of the claw opening/closing members in a movable manner individually, and a displacing member configured to displace the holding members together with the holding claws.

For example, after a workpiece having a certain shape is transported by operation of a displacing member, when another workpiece having a different shape is to be held, the claw opening/closing members can be moved to a position where it is possible to hold the workpiece. In this manner, in the present invention, by changing the position of the claw opening/closing member depending on the shape of the workpiece, it becomes possible to hold different shapes of workpieces.

Further, a plurality of holding claws are opened/closed individually. Therefore, for example, after operating one holding claw to change the orientation of the workpiece so that the workpiece can be held easily, by operating the remaining holding claws, it is possible to hold the workpiece. Also by changing the orientation of the workpiece in this manner, it is possible to hold different shapes of workpieces. It is a matter of course that these techniques of moving the claw opening/closing member, and opening/closing the holding claws individually may be adopted in combination.

Preferably, a magnet gripper configured to magnetically attract the workpiece may be provided for the holding claw. It is because, by this magnetic attraction, it is possible to prevent detachment of the workpiece from the holding claws.

Further, preferably, a contact part configured to be displaced in a direction closer to or away from the workpiece may be provided, and the contact part may be configured to contact the workpiece when the contact part is displaced to a position close to the workpiece. By bringing the contact part into contact with a portion of the workpiece, orientation of the workpiece is stabilized. Stated otherwise, sway of the workpiece is suppressed. Therefore, it becomes easy to deliver the transported workpiece to a predetermined position in a predetermined orientation.

Also in this contact part, the magnet gripper configured to magnetically attract the workpiece may be provided. In this case, for example, after the workpiece is temporarily magnetically attracted (held), and the workpiece can be transferred to the magnet gripper of the holding claws. Therefore, it is possible to change the orientation of the workpiece.

Further, for example, when the plurality of workpieces are magnetically attracted by the magnet gripper at the contact part, only one workpiece can be transferred to the magnet gripper of the holding claw. That is, it is possible to select only one workpiece to be transported.

For enabling movement of the claws opening/closing members, for example, a slit may be formed in the holding member. Further, by allowing the claw opening/closing member to move along the slit and to be fixedly positioned at the destination, it becomes possible to open/close the holding claw under operation of the claw opening/closing member at the destination.

In the structure, it is preferable to provide a guide member configured to guide the claw opening/closing member when the claw opening/closing member is displaced. Thus, it is possible to move the claw opening/closing members along the slits.

Though the number of holding claws is not limited specially, preferably, the number of the holding claws may be three or four. It is because, in this case, it is possible to hold the workpiece sufficiently stably, and avoid the use of excessive number of holding claws, and consequently, it is possible to avoid increase in the cost.

In the present invention, it is possible to move the claw opening/closing members, and open/close the holding claws individually. That is, it is possible to move the claw opening/closing members and the holding claws, and open/close the holding claws individually. Accordingly, it is possible to hold, and transport different shapes of workpieces in different orientations.

The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention is shown by way of illustrative example.

