Method and device for detecting plate thickness in press

• US 20030019266A1
• Filed: 08/15/2002
• Published: 01/30/2003
• Est. Priority Date: 02/18/2000
• Status: Active Grant

• Current Assignee: Amada Company Limited
• Original Assignee: Amada Company Limited
• Inventors: Kanno, Kazuhiro
• Granted Patent: US 6,826,939 B2
• Time in Patent Office: Days
• US Class Current: 72/19.9
• CPC Class Codes: B21D 5/02 on press brakes without making use of clamping means

Abstract

A ram (5U) is descended by a self-weight pressure of a rod-side cylinder chamber (19) of a hydraulic cylinder (13R) which vertically moves the ram (5U) is detected by oil pressure detection means (21), and a determination section (65) detects a position at which a punch (P) attached to the ram (5U) contacts with an upper surface of a workpiece (W), from a change of this detected pressure. If the upper surface of the workpiece (W) is detected, a plate thickness calculation section (67) calculates a plate thickness of the workpiece (W) based on an upper surface position of a die (D) known in advance and stored in a memory (63).

Claims

1. A plate thickness detection method for a press, comprising the steps of:

descending a ram from a certain height position;

detecting pressure of hydraulic oil discharged from a rod-side cylinder chamber at this time;

detecting time at which a punch contacts with a workpiece on the die, from a change of the detected pressure;

detecting upper and lower positions of the ram at this time;

obtaining a plate thickness of the workpiece from the detected height position of the ram and a set height between the certain height known in advance and an upper surface of the die; and

vertically moving the ram, to which the punch is attached, based on the obtained plate thickness of the workpiece, and pressing the workpiece cooperatively by the punch and the die.

2. A plate thickness detection method for a press according to claim 1, wherein

the ram is descended by a self-weight;

the pressure of the hydraulic oil discharged from the rod-side cylinder chamber at this time is detected; and

the time at which the punch contacts with the workpiece is detected from the change of the detected pressure.

3. A plate thickness detection method for a press according to claim 2, wherein

if the ram is to be descended by the self-weight, the ram is descended at a speed equal to or lower than a ram self-weight maximum falling speed at which the workpiece is not bent even if the punch contacts with the workpiece.

4. A plate thickness detection method for a press according to claim 3, wherein

time at which the pressure of the hydraulic oil discharged from the rod-side cylinder chamber changes from the pressure by the self-weight to atmospheric pressure, is detected as the time at which the punch contacts with the workpiece.

5. A plate thickness detection method for a press, comprising the steps of:

descending a ram from a certain height position while controlling a descent speed, and detecting a ram descent position;

detecting a ram stop position from a change of this detected ram position;

determining the detected stop position as a position at which a punch contacts with a workpiece on the die;

obtaining a plate thickness of the workpiece from the ram position which is determined as the position at which the punch contacts with the workpiece, and from a set height of a difference between the certain height known in advance and an upper surface of the die; and

vertically moving the ram, to which the punch is attached, based on the obtained plate thickness of the workpiece, and pressing the workpiece cooperatively by the punch and the die.

6. A plate thickness detection apparatus in a press, the detection apparatus comprising:

ram position detection section to detect upper and lower positions of a ram to which a punch is attached;

oil pressure detection section to detect pressure of hydraulic pressure discharged from a rod-side cylinder chamber of a hydraulic cylinder which vertically moves the ram;

a determination section detecting a position at which the punch contacts with a workpiece, from a change of the pressure detected by the oil pressure detection section; and

a plate thickness calculation section calculating a plate thickness of the workpiece, from the ram position which is determined by the determination section as position at which the punch contacts with the workpiece and from a set height of a difference between a certain height of the ram known in advance and an upper surface of the die, wherein

the ram is thereby vertically moved by the hydraulic cylinder, and the workpiece is pressed cooperatively by the punch and the die.

7. A plate thickness detection apparatus in a press according to claim 6, further comprising:

a ram self-weight maximum falling speed calculation section calculating a ram self-weight maximum falling speed at which the work is not bent even if the punch contacts with the workpiece if the ram is to be descended by a self-weight.

8. A plate thickness detection apparatus in a press, which vertically moves a ram, to which a punch is attached, by a hydraulic cylinder actuated by hydraulic oil from a two-way pump and which presses a workpiece cooperatively by the punch and a die, the apparatus comprising:

ram position detection section to detect upper and lower positions of the ram;

oil pressure detection section, provided halfway along a hydraulic circuit which connects a rod-side cylinder chamber of the hydraulic cylinder which vertically moves the ram, to the two-way pump, for detecting pressure of the hydraulic oil discharged from the rod-side cylinder chamber;

a determination section determining a position at which the punch contacts with the workpiece, from a change of the pressure of the hydraulic oil detected by the oil pressure detection section; and

a plate thickness calculation section calculating a plate thickness of the workpiece, from a ram position which is determined by the determination section as the position at which the punch contacts with the workpiece and from a set height of a difference between a certain height of the ram and an upper surface of the die.

9. A plate thickness detection apparatus in a press according to claim 8, wherein

the oil pressure detection section detects the pressure of the hydraulic oil discharged from the rod-side cylinder chamber when a speed switch valve provided halfway along the hydraulic circuit is switched to discharge the hydraulic oil from the rod-side cylinder chamber to the two-way pump and to descend the ram by a self-weight.

10. A plate thickness detection apparatus in a press according to claim 9, wherein

the determination section determines that time at which the pressure of the hydraulic oil discharged from the rod-side cylinder chamber detected by the oil pressure detection section changes from the pressure by a self-weight to atmospheric pressure, as time at which the punch contacts with the workpiece.

11. A plate thickness detection apparatus:

in a press according to claim 10, further comprising;

a ram self-weight maximum falling speed calculation section calculating a ram self-weight maximum falling speed at which the workpiece is not bent even if the punch contacts with the workpiece if the ram is to be descended by the self-weight.

12. A plate thickness detection apparatus in a press, which apparatus vertically moves a ram, to which a punch is attached. and which presses a workpiece cooperatively by the punch and a die, the apparatus comprising:

ram position detection section to descend the ram from a certain height position while controlling a descent speed, and for detecting a ram descent position;

a determination section detecting a ram stop position from a change of the ram position detected by the ram position section, and determining this detected stop position as a position at which the punch contacts with the workpiece; and

a plate thickness calculation section calculating a plate thickness of the workpiece, from the ram position determined by the determination section as the position at which the punch contacts with the workpiece and from a set height of a difference between the certain height known in advance and an upper surface of the die.