US3257810A

US3257810A - Hydraulic drive system for press brakes

Info

Publication number: US3257810A
Application number: US395473A
Authority: US
Inventors: Hanni Eduard
Original assignee: Individual
Current assignee: Individual
Priority date: 1963-09-12
Filing date: 1964-09-10
Publication date: 1966-06-28
Anticipated expiration: 1983-06-28
Also published as: CH409635A; AT241235B; GB1065443A

Description

June 28, 1966 E. HNNI HYDRAULIC DRIVE SYSTEM FOR PRESS BRAKES \\\\\\\\\\\w nmflwm United States Patent O 3,257,810 HYDRAULIC DRIVE SYSTEM FOR PRESS BRAKES Eduard Hnni, Rosengartenstrasse 10, Zofingen, Switzerland Filed Sept. 10, 1964, Ser. No. 395,473 Claims priority, application Austria, Sept. 12, 1963, A 7,339/ 63 2 Claims. (Cl. 60-54.5)

This invention relates to a hydraulic drive system for press brakes, and' particularly to a hydraulic drive system for a press 'brake in which an elongated beam is moved toward and away from a press bench in parallel alignment by means of two pistons or groups of pistons respectively engaging the end of the beam.

It is the object of this invention to provide a hydraulic system for a press brake of the type described in which parallel movement of the press beam relative to the bench is achieved in a simple and reliable manner.

A primary feature of the system of the invention is a pressure multiplier which is connected to a source of liquid at relatively low pressure and supplies liquid at higher pressure to the pistons which actuate movement of the press beam.

Other objects and features of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment of the invention as illustrated in the accompanying sheet of drawing whos-e sole figure shows the hydraulic system of a press brake partly in a conventional manner, and partly in elevational section.

Referring to the drawing in detail, there is shown a motor 1 which is coupled to a pump 2. The dischar-ge line 35 of the pump is equipped with a safety valve 3 and is connected to a three-way control valve 4. In the illustrated normal position of the valve, the discharge .line 35 communicates with a sump 10 through a return line 9, while a line 11 which leads from the valve 4 to a pressure multiplier 8 is blocked.

The valve 4 is electrically operated in a conventional manner by solenoids 4', 4 controlled by limit switches 37, 38 on the press. When the valve 4 is shifted toward the left from the illustrated position, fluid under pressure from the pump 2 enters the line 11. .If the valve 4 is shifted to the right from the illustrated normal position, the

lines

11 and 35 are both connected to the return line 9.

The pressure multiplier 8 has a cylinder cavity which is divided into two coaxial compartments 12, 13 by a partition 16. The cross section of the compartment 12 is somewhat smaller than that of the compartment 13. Pistons 14, 17 respectively arranged in the compartments 12, 13 are connected lby a common piston rod 15 which passes through the partition 16. The piston 17 has an annular face 18 about the rod 15, in a circular face 19.

Four axially elongated bores 20 communicate with the compartment 13 and are angularly spaced about the axis of the multiplier 8. Plungers 21 are respectively received in the bores 20 and normally abut against the face `19' of the piston 17. Only two of the 'bores 20 and the associated plungers 21 are visible in the drawing.

The two hydraulic cylinders 24, 25 which are connected to the press brake, not itself shown, near the ends of the beam, communicate with respective pairs of bores 20 by pressure lines 22, 23 equipped with compensating valves 36. A piston 33 is axially movable in each cylinder 24, 25. A stop 34 is arranged in each cylinder 24, 25 and is adjustable therein in a non-illustrated manner.

The control circuit of the pressure multiplier 8 further includes a plunger valve 26 and an auxiliary valve 27 which is electrically operated by a solenoid 27' and a limit switch 39, and is shifted into the illustrated position Patented June 28, 1966 ice when the brake beam reaches a certain position to close the switch 39.

The line 11 is permanently connected with a conduit 28" in the multiplier 8 which connects the portion of the compartment 13 adjacent the annular piston face 18 with the plunger valve 26. The valve 26 is also connected with the compartment 12 by a conduit 28', and with the auxiliary valve 27- by a conduit 31. The movements of the plunger 26 in the valve 26 are actuated by admission and release of fluid through a conduit 29 connected to the auxiliary -valve 27'. The last mentioned valve is also connected with the conduit 28 by a line 30, and with a sump 32.

The aforexlescribed hydraulic system is operated as follows:

The valve 4 is shifted toward the left so that hydraulic fluid ows from the discharge line 35 into the compartments 12, 13 through the line 11, the conduits 28', 28", and the open plunger valve 26.

Because the piston face 18 is greater than the corresponding annular face of the piston 12, the two pistons 14, 17 ymove rapidly in the direction of the arrow 34 under the small force exerted by fluid on the excess area of the piston face 18. As long as the press beam can move freely, it is quickly moved toward a work piece by the pistons 33.

The limit switch 39 is actuated by a moving element of the press brake, not itself shown, and triggers movement of the auxiliary valve 27 into the illustrated position. Pressure uid from the pump 2 is admitted to the conduit 29 by the valve 27, and the plunger-26' moves toward the right from the illustrated position to block Ithe orice of the conduit 28. The conduit 28" is simultaneously vented to the sump 32 by the valve 27. The full pump pressure acts on the frace 18 of the piston 17 whereas the piston 14 is relieved of fluid pressure.

The pistons 33 perform their power stroke under the pressure of fluid driven from the bores 20 by the plungers 21, and engage the stops 34. If unequal oil leakage from the two cylinders 24, 25 causes one piston 33 to engage its stop 34 before the other piston, the resulting high pressure in its associated pressure line 22 or 23 opens the compensating valve 36 in the line, and the amount of fluid in the twol hydraulic systems associated with the cylinders 24, 25 is balanced. This adjustment and' balancing occurs automatically during each operating cycle of the press brake.

When the control valve 4 is shifted toward the right, the pump discharge line 35 and the line 11 are connected to the sump 10.

The return arrangement which biases the press beam upwardly away from the 'bench causes the pistons 33 to expel fluid from the cylinders 24, 25. The plungers 21 move the pistons 14, 17 toward the illustrated position, and oil is displaced from the compartment 13 through the conduit 28, the lines 11 and 9 into the sump 10.

When the valve 4 returns to its normal illustrated position, the pump discharge line 35 is connected with the sump 10, and the line 11 is blocked.

The pressure multiplier and the associated elements thus provide high fluid pressure for operation of the press beam from a motor-driven pump which generates relatively low pressure. The parallel alignment of the press beam with the bench is automatically maintained. When the press operates against low resistance, the press beam is moved at high speed.

What is claimed is:

1. A hydraulic system comprising, in combination:

(a) a source of hydraulic fluid at relatively low pressure;

(b) two hydrauliccylinder means adapted to be connected to the two ends of a press brake beam;

(c) pressure multiplier means interposed between said source and said cylinders for supplying fluid at relatively high pressure to said cylinder means in response to the low pressure of the fiuid from said source, said pressure multiplier means including (1) means defining first and second cylinder compartments,

(2) a first piston and a second piston movably received in said compartments respectively, the effective piston area of said first piston being greater than the effective piston area of said secg ond piston,

(3) means defining first and second bores communieating with said first compartment (4) a first plunger and a second plunger movably received in said bores respectively and engageable with said first piston when the same moves in said first compartment in a predetermined direction to drive said plungers inward of the associated bores, and

(5) motion transmitting means fixedly connecting said first andsecond pistons for joint movement;

(d) valve means for connecting said source to said compartments, said valve means including a plurality of valve members movable relative to each other between (i) a first position in which said source is simultaneously connected to said compartment for applying the low pressure of said fiuid thereof to said first piston in a manner to move said first and second pistons jointly in said predetermined direction, and to said second piston in a manner to move said first and second pistons jointly in a direction opposite to said predetermined direction, whereby said pistons jointly move in said predetermined direction,

(ii) a second position in which said'source is connected to said first compartment for moving said pistons in said predetermined direction, while said second compartment is vented, and

(iii) a third position in which said first and second compartments are vented;

(e) two pressure lines respectively connecting said bores to said hydraulic cylinder means; and

(f) two compensating valve means respectively communicating with said pressure lines and responsive to a predetermined pressure therein for bleeding the associated pressure line,

(1) each hydraulic cylinder means including a cylinder member communicating with the associated pressure line, a piston member movable in said cylinder member in response to fluid pressure in said pressure line, and a stop mem- -ber arranged iin :the cylinder member for limiting the movement of said piston member.

2. A system as set forth in claim 1, wherein said valve means include a first valve having a plurality of connections respectively communicating with said source, with said iirst compartment, and with the atmosphere, a second valve interposed between said compartments, valve actuating means for moving said second valve between an open position thereof in which said second valve connects said compartments and a closed position, and a third valve operatively connected to said valve actuating means for venting said second compartment when said second valve is in said closed position.

References Cited by the Examiner UNITED STATES PATENTS 354,014 12/1886 Easton 91-165 X 1,084,512 1/1914 Weikel 91-165 X 1,239,862 9/1917 Baird 92--152 X 1,970,999 8/1934 Ferris et al. 6054.5 2,030,966 2/1936 Crane et al 60-52 2,032,185 2/1936 Sciaky 60-54.5 2,058,377 10/1936 Francis 60-54.5 X 2,308,712 1/1943 Peterson et al. 60-54.5 2,472,236 6/1949 Thomas 92-152 X 2,507,868 5/1950 -Purcell 60-52 2,608,059 8/1952 Kux 60-54.5 2,915,878 12/1959 Hramoff 60-54.5 2,916,205 12/1959 Litz 92-152 X FOREIGN PATENTS 1,099,682 3/1955 France.

560,678 4/ 1944 Great Britain.

SAMUEL LEVINE, Primary Examiner.

ROBERT R. BUNEVICH, Examiner.

Claims

1. A HYDRAULIC SYSTEM COMPRISING, IN COMBINATION: (A) A SOURCE OF HYDRAULIC FLUID AT RELATIVELY LOW PRESSURE; (B) TWO HYDRAULIC CYLINDER MEANS ADAPTED TO BE CONNECTED TO THE TWO ENDS OF A PRESS BRAKE BEAM; (C) PRESSURE MULTIPLIER MEANS INTERPOSED BETWEEN SAID SOURCE AND SAID CYLINDERS FOR SUPPLYING FLUID AT RELATIVELY HIGH PRESSURE TO SAID CYLINDER MEANS IN RESPONSE TO THE LOW PRESSURE OF THE FLUID FROM SAID SOURCE, SAID PRESSURE MULTIPLIER MEANS INCLUDING (1) MEANS DEFINING FIRST AND SECOND CYLINDER COMPARTMENTS, (2) A FIRST PISTON AND A SECOND PISTON MOVABLY RECEIVED IN SAID COMPARTMENTS RESPECTIVELY, THE EFFECTIVE PISTON AREA OF SAID FIRST PISTON BEING GREATER THAN THE EFFECTIVE PISTON AREA OF SAID SECOND PISTON, (3) MEANS DEFINING FIRST AND SECOND BORES COMMUNICATING WITH SAID FIRST COMPARTMENT (4) A FIRST PLUNGER AND A SECOND PLUNGER MOVABLY RECEIVED IN SAID BORES RESPECTIVELY AND ENGAGEABLE WITH SAID FIRST PISTON WHEN THE SAME MOVES IN SAID FIRST COMPARTMENT IN A PREDETERMINED DIRECTION TO DRIVE SAID PLUNGERS INWARD OF THE ASSOCIATED BORES, AND (5) MOTION TRANSMITTING MEANS FIXEDLY CONNECTING SAID FIRST AND SECOND PISTONS FOR JOINT MOVEMENT; (D) VALVE MEANS FOR CONNECTING SAID SOURCE TO SAID COMPARTMENTS, SAID VALVE MEANS INCLUDING A PLURALITY OF VALVE MEMBERS MOVABLE RELATIVE TO EACH OTHER BETWEEN (I) A FIRST POSITION IN WHICH SAID SOURCE IS SIMULTANEOUSLY CONNECTED TO SAID COMPARTMENT FOR APPLYING THE LOW PRESSURE OF SAID FLUID THEREOF TO SAID FIRST PISTON IN A MANNER TO MOVE SAID FIRST AND SECOND PISTONS JOINTLY IN SAID PREDETERMINED DIRECTION, AND TO SAID SECOND PISTON IN A MANNER TO MOVE SAID FIRST AND SECOND PISTONS JOINTLY IN A DIRECTION OPPOSITE TO SAID PREDETERMINED DIRECTION, WHEREBY SAID PISTONS JOINTLY MOVE IN SAID PREDETERMINED DIRECTION, (II) A SECOND POSITION IN WHICH SAID SOURCE IS CONNECTED TO SAID FIRST COMPARTMENT FOR MOVING SAID PISTONS IN SAID PREDETERMINED DIRECTION, WHILE SAID SECOND COMPARTMENT IS VENTED, AND (III) A THIRD POSITION IN WICH SAID FIRST AND SECOND COMPARTMENTS ARE VENTED; (E) TWO PRESSURE LINES RESPECTIVELY CONNECTING SAID BORES TO SAID HYDRAULIC CYLINDER MEANS; AND (F) TWO COMPENSATING VALVE MEANS RESPECTIVELY COMMUNICATING WITH SAID PRESSURE LINES AND RESPONSIVE TO A PREDETERMINED PRESSURE THERIN FOR BLEEDING THE ASSOCIATED PRESSURE LINE, (1) EACH HYDRAULIC CYLINDER MEANS INCLUDING A CYLINDER MEMBER COMMUNICATING WITH THE ASSOCIATED PRESSURELINE, A PISTON MEMBER MOVABLE IN SAID CYLINDER MEMBER IN RESPONSE TO FLUID PRESSURE IN SAID PRESSURE LINE, AND A STOP MEMBER ARRANGED IN THE CYLINDER MEMBER FOR LIMITING THE MOVEMENT OF SAID PISTON MEMBER.