Method and apparatus for diagnosing press cushioning device, on optimum range of blank-holding force

An apparatus for diagnosing a cushioning device of a press having an upper die and a lower die which cooperate to perform a pressing action on a blank during a downward movement of said upper die, and a pressure member which cooperates with said upper die to hold said blank during said pressing action, said cushioning device including (a) force generating means for generating a blank-holding force, (b) a cushion platen disposed below said lower die and receiving said blank-holding force, (c) a plurality of balancing hydraulic cylinders disposed on said cushion platen and having fluid chambers communicating with each other, and (d) a plurality of cushion pins associated at lower ends thereof with said hydraulic cylinders, respectively, and supporting at upper ends thereof said pressure member, and wherein said blank is held by said upper die and said pressure member during said pressing action by said blank-holding force which is transmitted to said pressure member through said cushion platen, said hydraulic cylinders and said cushion pins such that said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders, said apparatus comprising:

• force changing means for changing said blank-holding force generated by said force generating means;
• hydraulic pressure detecting means for detecting said hydraulic pressure in said balancing hydraulic cylinder under operation to transmit said blank-holding force to said pressure member, as said blank-holding force is changed;
• change rate calculating means for calculating a rate of change of said hydraulic pressure detected by said hydraulic pressure detecting means, as said blank-holding force is changed;
• diagnosing means for diagnosing said cushioning device on the basis of said rate of change of the detected hydraulic pressure calculated by said change rate calculating means, regarding an optimum range of said blank-holding force in which said rate of change of said detected hydraulic pressure is substantially constant;
• and
• indicating means for indicating a result of a diagnosis effected by said diagnosing means.

A method of diagnosing a cushioning device of a press having an upper die and a lower die which cooperate to perform a pressing action on a blank during a downward movement of said upper die, and a pressure member which cooperates with said upper die to hold said blank during said pressing action, said cushioning device including (a) force generating means for generating a blank-holding force, (b) a cushion platen disposed below said lower die and receiving said blank-holding force, (c) a plurality of balancing hydraulic cylinders disposed on said cushion platen and having fluid chambers communicating with each other, and (d) a plurality of cushion pins associated at lower ends thereof with said hydraulic cylinders, respectively, and supporting at upper ends thereof said pressure member, and wherein said blank is held by said upper die and said pressure member during said pressing action by said blank-holding force which is transmitted to said pressure member through said cushion platen, said hydraulic cylinders and said cushion pins such that said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders, said method comprising the steps of:

• detecting a hydraulic pressure in said balancing hydraulic cylinders during operation thereof to transmit said blank-holding force to said pressure member, as said blank-holding force is changed;
• calculating a reference value on the basis of specifications of said cushioning device, said reference value representing a rate of change of the detected hydraulic pressure with a change of said blank-holding force which occurs within an optimum range in which said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders;
• calculating said rate of change of said detected hydraulic pressure as said blank-holding force is changed;
• and
• diagnosing said cushioning device such that a range of said blank-holding force in which the calculated rate of change of said hydraulic pressure is substantially equal to said reference value is determined as said optimum range.

An apparatus for diagnosing a cushioning device of a press having an upper die and a lower die which cooperate to perform a pressing action on a blank during a downward movement of said upper die, and a pressure member which cooperates with said upper die to hold said blank during said pressing action, said cushioning device including (a) force generating means for generating a blank-holding force, (b) a cushion platen disposed below said lower die and receiving said blank-holding force, (c) a plurality of balancing hydraulic cylinders disposed on said cushion platen and having fluid chambers communicating with each other, and (d) a plurality of cushion pins associated at lower ends thereof with said hydraulic cylinders, respectively, and supporting at upper ends thereof said pressure member, and wherein said blank is held by said upper die and said pressure member during said pressing action by said blank-holding force which is transmitted to said pressure member through said cushion platen, said hydraulic cylinders and said cushion pins such that said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders, said apparatus comprising:

• force changing means for changing said blank-holding force generated by said force generating means;
• hydraulic pressure detecting means for detecting a hydraulic pressure in said balancing hydraulic cylinders during operation thereof to transmit said blank-holding force to said pressure member, as said blank-holding force is changed;
• reference calculating means for calculating a reference value on the basis of specifications of said cushioning device, said reference value representing a rate of change of the detected hydraulic pressure with a change of said blank-holding force which occurs within an optimum range in which said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders;
• change rate calculating means for calculating said rate of change of said detected hydraulic pressure as said blank-holding force is changed;
• diagnosing means said cushioning device such that a range of said blank-holding force in which the calculated rate of change of said hydraulic pressure is substantially equal to said reference value is determined as said optimum range;
• and
• indicating means for indicating a result of a diagnosis effected by said diagnosing means.

A method of diagnosing a cushioning device of a press having an upper die and a lower die which cooperate to perform a pressing action on a blank during a downward movement of said upper die, and a pressure member which cooperates with said upper die to hold said blank during said pressing action, said cushioning device including (a) force generating means for generating a blank-holding force, (b) a cushion platen disposed below said lower die and receiving said blank-holding force, (c) a plurality of balancing hydraulic cylinders disposed on said cushion platen and having fluid chambers communicating with each other, and (d) a plurality of cushion pins associated at lower ends thereof with said hydraulic cylinders, respectively, and supporting at upper ends thereof said pressure member, and wherein said blank is held by said upper die and said pressure member during said pressing action by said blank-holding force which is transmitted to said pressure member through said cushion platen, said hydraulic cylinders and said cushion pins such that said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders, said method comprising the steps of:

• detecting said blank-holding force generated by said force generating means;
• detecting a hydraulic pressure in said balancing hydraulic cylinders during operation thereof to transmit said blank-holding force to said pressure member;
• diagnosing said cushioning device such that the detected blank-holding force is held within an optimum range in which said blank-holding force is substantially evenly distributed on all of said cushion pins by said balancing hydraulic cylinders, if said detected blank-holding force and the detected hydraulic pressure of said hydraulic cylinders satisfy a predetermined formula which is formulated on the basis of specifications of said cushioning device.

An apparatus for diagnosing a cushioning device of a press having an upper die and a lower die which cooperate to perform a pressing action on a blank during a downward movement of said upper die, and a pressure member which cooperates with said upper die to hold said blank during said pressing action, said cushioning device including (a) force generating means for generating a blank-holding force, (b) a cushion platen disposed below said lower die and receiving said blank-holding force, (c) a plurality of balancing hydraulic cylinders disposed on said cushion platen and having fluid chambers communicating with each other, and (d) a plurality of cushion pins associated at lower ends thereof with said hydraulic cylinders, respectively, and supporting at upper ends thereof said pressure member, and wherein said blank is held by said upper die and said pressure member during said pressing action by said blank-holding force which is transmitted to said pressure member through said cushion platen, said hydraulic cylinders and said cushion pins such that said blank-holding force is substantially evenly distributed on all of said cushion pins by said hydraulic cylinders, said apparatus comprising:

• force detecting means for detecting said blank-holding force generated by said force generating means;
• hydraulic pressure detecting means for detecting a hydraulic pressure in said balancing hydraulic cylinders during operation thereof to transmit said blank-holding force to said pressure member;
• diagnosing means for diagnosing said cushioning device such that the detected blank-holding force is held within an optimum range in which said blank-holding force is substantially evenly distributed on all of said cushion pins by said balancing hydraulic cylinders, if said detected blank-holding force and the detected hydraulic pressure of said hydraulic cylinders satisfy a predetermined formula which is formulated on the basis of specifications of said cushioning device.