Optical safety device for press brake, press brake, and optical monitoring method

Patent metadata

Field	Value
Publication number	US-11623267-B2
Application number	US-201916979599-A
Country	US
Kind code	B2
Filing date	Mar 12, 2019
Priority date	Mar 14, 2018
Publication date	Apr 11, 2023
Grant date	Apr 11, 2023

Abstract

A determination part determines whether or not a shadow of an upper mold is expanded to a photodiode by laser beam projected to a light receiver side based on a light receiving state of a photodiode positioned in a vicinity of the upper mold. When it is determined that the shadow of the upper mold is expanded to the photodiode positioned in the nearest vicinity of the upper mold, the invalidation unit invalidates the photodiode. A detection unit detects a presence or absence of a foreign body between the upper mold and a lower mold based on light receiving states of the effective plurality of photodiodes during a lowering operation of an upper table.

First claim

The invention claimed is:

1. An optical safety device for a press brake comprising:
a projector provided on one side in a length direction of an upper table in the press brake for projecting a monitoring light directly under an upper tool and toward the other side in the length direction of the upper table;
a photodetector provided on the other side in the length direction of the upper table and having a plurality of light receiving elements for outputting electric signals corresponding to an amount of the monitoring light, and for receiving the monitoring light;
a first sensor that acquires a member temperature of the upper tool, and a second sensor that acquires an environmental temperature in which the press brake is installed:
a calculation unit for calculating an amount of enlargement of the shadow of the upper tool generated by refracting the monitoring light projected by the projector, based on at least the member temperature of the upper tool acquired by the first sensor and the environmental temperature in which the press brake is installed acquired by the second sensor;
a determination unit for determining whether or not a shadow of the upper tool extends to a light receiving element of the plurality of light receiving elements located closest to the upper tool based on the calculated amount of enlargement of the shadow of the upper tool before the press brake starts a lowering operation of the upper table relative to the lower table in the press brake;
an invalidation unit configured to invalidate the light receiving element located closest to the upper tool when it is determined that the shadow of the upper tool extends to the light receiving element located closest to the upper tool; and
a detector for detecting a presence or absence of a foreign body between the upper tool and the lower tool based on a respective light receiving state of each light receiving element of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool by detecting whether or not the amount of monitoring light received by any one of the light receiving elements of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool is equal to or less than a respective predetermined threshold value when it is determined that the shadow of the upper tool extends to the light receiving element located closest to the upper tool during the lowering operation of the upper table relative to the lower table.

2. The optical safety device according to claim 1 , wherein the optical safety device is provided with a changeover switch for switching the light receiving element located closest to the upper tool to an invalidated state, and the invalidating unit invalidates the light receiving element located closest to the upper tool when the changeover switch is operated.

3. A press brake including the optical safety device according to claim 1 .

4. An optical monitoring method, by using a light projector provided on one side in a length direction of an upper table in a press brake for projecting monitoring light directly under an upper tool toward other side in the length direction of the upper table and a plurality of light receiving elements provided on the other side in the length direction of the upper table and receiving the monitoring light, for monitoring a presence or an absence of a foreign substance between the upper tool and a lower tool based on respective light receiving states of each of the plurality of light receiving elements in a photodetector, comprising;
a step of acquiring a member temperature of the upper tool by a first sensor, and an environmental temperature in which the press brake is installed by a second sensor,
a step of calculating an amount of enlargement of the shadow of the upper tool generated by refracting the monitoring light projected by the projector, based on at least the member temperature of the upper tool acquired b the first sensor and the environmental temperature in which the press brake is installed acquired by the second sensor,
a step of determining whether or not a shadow of the upper tool is expanded to a light receiving element of the plurality of light receiving elements located closest to the upper tool based on the calculated amount of enlargement of the shadow of the upper tool, before the press brake starts a lowering operation of the upper table relative to the lower table in the press brake,
a step of invalidating the light receiving element located closest to the upper tool when it is determined that the shadow of the upper tool extends to the light receiving element located closest to the upper tool, and
a step of detecting a presence or absence of a foreign body between the upper tool and the lower tool based on the respective light receiving state of each light receiving element of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool by detecting whether or not an amount of monitoring light received by any one of the light receiving elements of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool is equal to or less than a respective predetermined threshold value when it is determined that the shadow of the upper tool extends to the light receiving element located closest to the upper tool during the lowering operation of the upper table relative to a lower table.

5. An optical safety device for a press brake comprising:
a projector provided on one side in a length direction of an upper table in the press brake for projecting a monitoring light directly under an upper tool and toward the other side in the length direction of the upper table;
a photodetector provided on the other side in the length direction of the upper table and having a plurality of light receiving element for outputting electric signals corresponding to amount of the monitoring light and receiving the monitoring light;
a first sensor that acquires a member temperature of the upper tool, and a second sensor that acquires an environmental temperature in which the press brake is installed:
a calculation unit for calculating an amount of enlargement of the shadow of the upper tool generated by refracting the monitoring light projected by the projector, based on at least the member temperature of the upper tool acquired by the first sensor and the environmental temperature in which the press brake is installed acquired by the second sensor;
an invalidation unit configured to invalidate a light receiving element located closest to the upper tool when a shadow of the upper tool projected on the photodetector by the monitoring light extends to the light receiving element located closest to the upper tool based on the calculated amount of enlargement of the shadow of the upper tool before starting a lowering operation of the upper table relative to the lower table; and
a detector for detecting a presence or absence of a foreign body between the upper tool and the lower tool based on a respective light receiving state of each light receiving element of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool by detecting whether or not the amount of monitoring light received by any one of the light receiving elements of the plurality of light receiving elements other than the invalidated light receiving element located closest to the upper tool is equal to or less than a respective predetermined threshold value when it is determined that the shadow of the upper tool extends to the light receiving element located closest to the upper tool during the lowering operation of the upper tabl

Assignees

• Amada Co Ltd

Inventors

• Matsuura Kento

Classifications

• B21D55/00 Primary

  Safety devices protecting the machine or the operator, specially adapted for apparatus or machines dealt with in this subclass (for presses in general B30B; safety devices in general F16P) · CPC title

• B21D5/0209

  Tools therefor · CPC title

• F16P3/144

  using light grids · CPC title

• B30B15/285

  preventing a full press stroke if there is an obstruction in the working area · CPC title

• B21D5/02

  on press brakes without making use of clamping means · CPC title