Metal deforming – With means to drive tool – Including pneumatic- or fluid-actuated tool support
Patent
1996-12-17
1998-09-29
Jones, David
Metal deforming
With means to drive tool
Including pneumatic- or fluid-actuated tool support
100259, 267119, B21D 2408
Patent
active
058132759
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a safety circuit for a press die cushion arrangement whereby a pad is prevented from being lifted up and down unintentionally.
BACKGROUND ART
Conventionally, a press machine for performing a draw forming operation has customarily been equipped with a die cushion arrangement.
A die cushion in the prior art comprises a pad that is adapted to support a plurality of cushion pins from a downward side and a cushion cylinder that comprises an air cylinder which is adapted to support the said pad resiliently. And, in combination within a locking cylinder that comprises a hydraulic cylinder in place of an air cylinder, a die cushion arrangement that is capable of temporarily locking the pad and hence having a locking function has hitherto be employed. Such a die cushion arrangement has been disclosed, for example, in Japanese Examined Patent Publication No. Sho 52-23107, Japanese Unexamined Patent Publication No. Sho 58-70998, Japanese Unexamined Patent Publication No. Sho 58-70999 and Japanese Examined Utility Model Publication No. Hei 5-254.
A known, a circuit for a die cushion having a locking function for a pad is illustrated in FIGS. 1 and 2.
More specifically, each of the both circuits comprises a pressure conditioning circuit a for adjusting a plant air to a specified pressure and supplying the adjusted air to an air reservoir b, an air reservoir circuit e for compensating for a change in the air pressure within each of a pair of cushion cylinders d when the pad c is cushion operated, an air supply valve 1 interposed between the air reservoir b and the cushion cylinders d for operating an upward movement and a downward movement of each of the cushion cylinders d, one or a plurality of electromagnetic valve f for establishing and blocking a supply of a pilot pressure to the air supply valve 1, a regulator g for conditioning the said pilot pressure, a manually operated pressure conditioning circuit h for substituting for the above mentioned pressure conditioning circuit a when the latter fails, a locking cylinder i for locking the pad c and a locking circuit j therefor.
And, in a circuit shown in FIG. 1 the electromagnetic valve f may comprise the "both SOL" (both side solenoid) type in which the value may be switched electrically in both directions, whereas in a circuit shown in FIG. 2 the electromagnetic valve f may comprise the "one side SOL" (one side solenoid) type in which the value may be electrically switched in a single direction and thereafter returned to its neutral position by a spring in the other direction.
In a circuit in which the electromagnetic valve f makes use of a "both side SOL" as shown in FIG. 1, if the power supply is turned OFF due to an emergency stop or the like during a pressing operation, the electromagnetic valve f remains at the position in which it had been so that the pad c lying at its upper limit position or the pad c lying at its lower limit position may not be unintentionally lifted downwards or upwards; hence t he system is safe.
However, it has recently become customary for the purpose of an energy saving to turn the plant air source OFF while the press machine ceases performing its pressing operation.
For this reason, the pad c that has been at its upper limit position at the end of a pressing operation may slowly descend according to a pressure drop due to a fluid leakage in the cushion cylinder d or in its circuit to come to a stop at its lower limit position. Accordingly, there has always been the problem that when the plant air source is turned ON to initiate a pressing operation the next day, contrary to the operator's intent the pad c may be suddenly lifted upwards to the extent that if the operator is present in the press machine, he or she will be exposed to danger.
Also, if the press machine is a suction operated workpiece conveyance transfer press in which a workpiece is attracted in a state where the pad is locked, turning the power supply OFF in situ when the press machine is emergency stopped due to a fai
REFERENCES:
patent: 4635466 (1987-01-01), Seki et al.
patent: 5295383 (1994-03-01), Kirii et al.
patent: 5299444 (1994-04-01), Kirii et al.
patent: 5457980 (1995-10-01), Kirii et al.
Kawakami Yasuo
Suzuki Masami
Jones David
Komatsu Ltd.
LandOfFree
Safety circuit for press die cushion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Safety circuit for press die cushion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Safety circuit for press die cushion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-677140