EP-4741077-A1 - GRIPPER FOR TRANSFER SYSTEM AND TRANSFER SYSTEM COMPRISING SUCH A GRIPPER

EP4741077A1EP 4741077 A1EP4741077 A1EP 4741077A1EP-4741077-A1

Abstract

Gripper for a stamping press having a transfer system, said gripper having a first and a second gripping arm for gripping a sheet to be stamped and a supporting body in which an actuating piston unit is housed, said piston unit being capable of actuating, via a longitudinal piston rod of the piston unit, said first gripping arm of the part to be stamped, said first arm being articulatedly connected to the supporting body, characterized in that the piston unit comprises at least two pistons in line with each other, separated and configured to work simultaneously and independently by actuating said piston rod.

Inventors

SARABIA TRILLA, MIGUEL

Assignees

Misati, S.L.

Dates

Publication Date: 20260513
Application Date: 20251104

Claims (14)

Gripper for a stamping press having a transfer system, said gripper having a first and a second gripping arm for gripping a sheet to be stamped and a supporting body in which an actuating piston unit is housed, said piston unit being capable of actuating, via a longitudinal piston rod of the piston unit, said first gripping arm of the part to be stamped, said first arm being articulatedly connected to the supporting body, characterized in that the piston unit comprises at least two pistons in line with each other, separated and configured to work simultaneously and independently by actuating said piston rod.
Gripper according to the preceding claim, characterized in that said piston unit comprises two chambers, each chamber having its corresponding pneumatic fluid inlet and a corresponding piston, both pistons being connected to the longitudinal piston rod of the piston unit in such a way that both pistons exert cumulative forces on said longitudinal piston rod.
Gripper according to the preceding claim, characterized in that each chamber has a front stop for the corresponding piston, the front stop separating both chambers from the rear chamber.
Gripper according to any one of the preceding claims, in which the second arm is a fixed gripping arm which is fixedly attached to the supporting body.
Gripper according to any one of the preceding claims, characterized in that said first arm has an end with at least one tip for gripping the sheet to be stamped.
Gripper according to the preceding claim, characterized in that said at least one tip has at its end a profiled ball and socket joint for contact with the sheet, the ball and socket joint being able to rotate with respect to the tip.
Gripper according to Claim 5 or 6, characterized in that said first arm comprises two gripping tips parallel to each other and connected to a compensating arm fixed to the first arm in a tilting manner, in which the compensating arm is arranged perpendicularly with respect to the tips, said arm being able to rotate with respect to an axis perpendicular to the longitudinal direction of the tips and perpendicular to the longitudinal direction of the compensating arm.
Gripper according to any one of the preceding claims, characterized in that said first arm comprises a guide for an actuating bearing which is jointly attached to the longitudinal piston rod of the piston unit.
Gripper according to the preceding claim, characterized in that the supporting body comprises at least one guide for the aforementioned actuating bearing, the path of said guide being parallel to the movement of the aforementioned longitudinal piston rod in the piston unit.
Gripper according to any one of the preceding claims, characterized in that the movable arm is articulated with respect to the supporting body around a pivot located between the longitudinal piston rod and the fixed arm.
Transfer system comprising: - a guide comprising two approximately parallel section members - a series of positions arranged along the guide, each position comprising, in each of said two section members, a transport element capable of back-and-forth movement along the track and a workpiece gripping element - means for synchronizing the transport elements and the gripping elements for taking the workpiece from an upstream position and/or transferring it to a downstream position, in which at least one of the gripping elements is said at least one gripper according to any one of the preceding claims.
Transfer system according to the preceding claim, characterized in that said gripper is arranged between the guide and the workpiece, with the longitudinal direction of the pneumatic piston unit of the gripper parallel to the distance separating the guide and the workpiece.
Transfer system according to Claim 11 or 12, characterized in that each of the positions corresponds to a die.
Transfer system according to any one of Claims 11 to 13, characterized in that the workpiece is a metal sheet.

Description

The present invention relates to a gripper for a stamping press having a transfer system, (also called "handling system" or "conveyor system") as well as a transfer system for a stamping press incorporating such a gripper. Stamping presses are commonly used in industry, in particular in the motor industry, for the shaping of metal workpieces, such as, for example, sheets. These presses include an automatic workpiece positioning and transfer system, commonly referred to as a "conveyor system", 'transfer system' or 'transfer'. Through this system a workpiece can be sequentially stamped and die-cut along a plurality of dies arranged in the press. In the industry, workpieces are commonly referred to as sheets, irrespective of their shape. Both terms will be used interchangeably in the present description. The aforementioned automated positioning and transfer system typically includes a series of pneumatic grippers distributed along a linear path. Generally, the grippers are positioned along a pair of gripper-holder profiles that lie parallel or nearly parallel to each other on both sides of consecutive stamping dies in the press. Both gripper-holder profiles are coupled to bars of the transfer system of the press. These bars are able to perform a back-and-forth movement with a component in the forward direction of the workpieces to be stamped, enabling a group of grippers associated with the same die to hold a sheet to be stamped, transfer it to the next die and move back to its original position while the sheet stamping operation is carried out. This process is repeated with subsequent workpieces that are to be stamped or die-cut. Pneumatic grippers for stamping presses having a transfer system generally comprise gripping arms for the sheet to be stamped and a supporting body with an inner cavity which houses a single piston unit actuated by a pneumatic system. This pneumatic piston unit has the function of actuating one or more gripping arms of the gripper, which is/are hinged to the supporting body. Each of the grippers may include lines supplying the piston unit's pneumatic circuit and electrical cables that power one or more sensors to detect the presence of the sheet to be stamped. The gripping arms may be of different types, such as, for example, a fixed arm and a movable arm, or all the arms may be movable. In transfer system grippers, both the arms and the piston unit are in line and positioned in a direction approximately perpendicular to the gripper holders, between the sheet and the gripper holders. Documents ES2668371T3 and ES2798024 disclose pneumatic transfer system grippers of this type. When in operation, all the gripper devices of a conveyor (transfer) system are synchronized to simultaneously remove a sheet from one die and transfer it to the next. Efficient gripping of the sheet during transfer ("conveying") is of vital importance for correct delivery to the next die in the transfer system. The workstations are referred to in the industry as "dies". Stamping processes with presses that include a conveyor system are intended to increase output (i.e. increase the number of workpieces per minute) by increasing the working speed of the system. As the speed increases, acceleration and deceleration of the conveying movement of the gripper with the gripped sheet are also increased. However, the higher the speed of the system, the more force the gripper must exert on the sheet to avoid problems. A first problem that can arise due to insufficient gripping force on the sheet is that the sheet may fall off. Another problem that can occur is that the sheet held by one or more grippers may slip or turn (without falling), which disrupts the entire stamping process and can lead to a serious accident, e.g. when a sheet to be stamped is incorrectly positioned in the next die. Such an incident of incorrect positioning of the sheet can stop the entire stamping process, with an adverse impact on the performance of the entire press (not just that die), and may even damage the die itself. This problem of insufficient gripping of the sheets by the grippers is magnified and becomes even more relevant when using presses where the workpieces are cantilevered, as in this case they are only gripped on one side. When gripping the cantilevered sheet, the gripping force on the sheet must be greater so as to counteract the weight of the sheet and the accelerations to which it is subjected at a single point. However, in industry it is common to work with cantilevered workpieces, as this allows two workpieces to be stamped opposite to each other at the same time, each gripped on one side, which doubles production. The problem of inadequate gripping of workpieces is also magnified by the tendency to design workpieces or sheets of considerable length in which the centre of mass is far away from the gripping point. One possible solution to increase the gripping force of the grippers could be to increase their size. However, ano