Control system for hydraulic presses

Claim 2

In a hydraulic press of the type having a lower platen, an upper platen movable by a ram slidable in a cylinder, the cylinder having a head end and a rod end, and the press having a hydraulic fluid system for driving the ram through a work stroke and a return stroke, the combination of: motorized pump means in said fluid system for pumping hydraulic fluid under pressure from a reservoir into said cylinder; valve means in said hydraulic fluid system comprising a plurality of relatively small, solenoid-actuated, pressure relief valves for sequencing said press by applying or relieving pressure in said cylinder; electric means, including electric switches, in an electric circuit for actuating said valve means; control means for actuating said switches in accordance with the movement of said upper platen, said control means including tripping mechanism, operable to actuate one of said switches to electrically actuate one of said valves to instantaneously relieve pressure in the head end of said cylinder, at a predetermined point in said work stroke for preventing work-piece breakthrough shock and high speed cycling means, actuated by the tripping mechanism of said control means, for sequencing said ram for a high speed return stroke, a high speed work stroke until work contact and a slow speed work-piece penetration stroke.

Claim 3

A hydraulic press as specified in claim 1 wherein: said pump means forms part of said high speed cycling means and comprises a double pump consisting of two pump cartridges in one common pump body, one cartridge being large-volume, low-pressure, and the other cartridge being small-volume, high-pressure.

Claim 4

A hydraulic press as specified in claim 1, wherein: said pump means comprises a large-volume, low pressure pump and a small-volume, high-pressure pump, both feeding the head end of said cylinder on the work stroke; and said control means includes a valve for diverting fluid from said large-volume pump from the head end of said cylinder to said reservoir to slow said ram, when a work-piece is contacted on said work stroke, thereby causing said small-volume pump to complete the work stroke through the work-piece.

Claim 5

A hydraulic press as specified in claim 1, wherein: said pump means includes a high-volume, low-pressure pump and a small-volume, high-pressure pump for driving said ram on the work stroke, said control means includes a valve for diverting said high-volume, low pressure pump from the head end of said cylinder to said reservoir to leave said small-volume, high-pressure pump driving said ram alone upon contact with a work-piece, and said mechanism for tripping said one switch to relieve pressure in the head end of said cylinder is operable to relieve the high pressure therein created by said small volume pump just before breakthrough of a work-piece.

Claim 6

In a hydraulic press of the type having a lower platen, an upper platen movable by a ram slidable in a cylinder, the cylinder having a head end and a rod end, and the press having a hydraulic Fluid system with motorized pump means for driving the ram through a work stroke and a return stroke, the combination of: valve means in said hydraulic system comprising a plurality of individual, solenoid-actuated, pressure relief valves for sequencing said press by applying and relieving pressure in said cylinder; electric means, including an electric circuit, the solenoids of said valves and a plurality of electric switches for actuating said solenoids; breakthrough shock avoidance means, including trip mechanism operable at a predetermined point on the path of said movable platen to actuate one of said switches to instantaneously close said electric circuit and energize one of said solenoid valves to relieve pressure in the head end of said cylinder; and high speed cycling means, including a large-volume, low-pressure pump and a small-volume, high-pressure pump in said pump means, and including trip mechanism operable by said movable platen to actuate said switches and energize said valves to sequence said ram for a high speed return stroke with both said pumps, a high speed work stroke with both said pumps until the work-piece is contacted and a slow speed work-piece penetration stroke with only said high-pressure, small-volume pump.

Claim 7

In a hydraulic press of the type having a lower platen, an upper platen movable by a ram slidable in a cylinder, the cylinder having a head end and a rod end, and the press having a hydraulic Fluid system with motorized pump means for driving the ram through a work stroke and a return stroke, the combination of: valve means in said hydraulic system comprising a plurality of individual, solenoid-actuated, pressure relief valves for sequencing said press by applying and relieving pressure in said cylinder; electric means, including an electric circuit, the solenoids of said valves and a plurality of electric switches for actuating said solenoids; breakthrough shock avoidance means, including trip mechanism operable at a predetermined point on the path of said movable platen to actuate one of said switches to instantaneously close said electric circuit and energize one of said solenoid valves to relieve pressure in the head end of said cylinder; and high speed cycling means, including a large-volume, low-pressure pump and a small-volume, high-pressure pump in said pump means, and including trip mechanism operable by said movable platen to actuate said switches and energize said valves to sequence said ram for a high speed return stroke with both said pumps, a high speed work stroke with both said pumps until the work-piece is contacted and a slow speed work-piece penetration stroke with only said high-pressure, small-volume pump.

Claim 8

In a hydraulic press having a platen movable by a ram slidable in a cylinder, the cylinder having a head end and a ram end, the combination of: high speed cycling means comprising a pair of pumps both connected to said cylinder, said pumps consisting of a small volume, high-pressure pump and a large-volume, low-pressure pump; electric means, including a plurality of small, solenoid-actuated, pressure relief valves, each energized by a switch in an electric circuit, said means sequencing said press; and control means for opening or closing the switches in said circuit to connect both said pumps to the rod end of said cylinder on the return stroke of said ram, to connect both said pumps to the head end of said cylinder on the work stroke of said ram until the work-piece is contacted, thereby moving said ram at high speed, and to connect only said high-pressure pump to said head end during the work-piece penetration portion of said work stroke, while diverting said large-volume pump to the reservoir of said press.

Claim 9

In a hydraulic press having a platen movable by a ram slidable in a cylinder, the cylinder having a head end and a ram end, the combination of: high speed cycling means comprising a pair of pumps both connected to said cylinder, said pumps consisting of a small volume, high-pressure pump and a large-volume, low-pressure pump; electric means, including a plurality of small, solenoid-actuated, pressure relief valves, each energized by a switch in an electric circuit, said means sequencing said press; and control means for opening or closing the switches in said circuit to connect both said pumps to the rod end of said cylinder on the return stroke of said ram, to connect both said pumps to the head end of said cylinder on the work stroke of said ram until the work-piece is contacted, thereby moving said ram at high speed, and to connect only said high-pressure pump to said head end during the work-piece penetration portion of said work stroke, while diverting said large-volume pump to the reservoir of said press.

Claim 10

In a hydraulic press having a platen movable by a ram slidable in a cylinder, the cylinder having a head end and a ram end, the combination of: breakthrough shock avoidance means, including trip mechanism operable at a predetermined point on the path of said movable platen to actuate an electric switch just before male dies break through a work-piece; valve means, including a solenoid-actuated, pressure relief valve in the pressure line leading to the head end of said cylinder for normally feeding hydraulic fluid thereto when open, but for relieving pressure therein when closed; electric control circuit means, including a source of current, said switch and the coil of said solenoid for instantaneously closing said valve means when said switch is actuated to relieve pressure in the head end of said cylinder just before said male dies break through a work-piece and high speed cycling means, including a large-volume, low-pressure pump, a small-volume, high-pressure pump, said valve means and said circuit means for driving said ram at high speed on a return stroke, at high speed on a work stroke until contact with a work-piece and at slow speed on a work penetration stroke.

Claim 11

In a hydraulic press having a platen movable by a ram slidable in a cylinder, the cylinder having a head end and a ram end, the combination of: breakthrough shock avoidance means, including trip mechanism operable at a predetermined point on the path of said movable platen to actuate an electric switch just before male dies break through a work-piece; valve means, including a solenoid-actuated, pressure relief valve in the pressure line leading to the head end of said cylinder for normally feeding hydraulic fluid thereto when open, but for relieving pressure therein when closed; electric control circuit means, including a source of current, said switch and the coil of said solenoid for instantaneously closing said valve means when said switch is actuated to relieve pressure in the head end of said cylinder just before said male dies break through a work-piece and high speed cycling means, including a large-volume, low-pressure pump, a small-volume, high-pressure pump, said valve means and said circuit means for driving said ram at high speed on a return stroke, at high speed on a work stroke until contact with a work-piece and at slow speed on a work penetration stroke.