US3031950A - Hydraulic press - Google Patents

Description

May 1, 1962 R. P. ANDERSON ET A. 3,031,950

HYDRAULIC PRESS 5 Sheets-Sheet 1 Filed June 5, 1959 Num/j,

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Filed June 5, 1959 INVENTORS @MH E AMM-@50N By IPOY N May 1, 1962 R. P. ANDERSON ET AL 3,031,950

HYDRAULIC PRESS Filed June 5, 1959 5 Sheets-Sheet 5 INVENToRs PAL PH R A/voE/sa/ BY foy DEH/v Ar rae/EVS United States Patent O Ohio Filed June 5, 1959, Ser. No. 818,411 5 Claims. (Cl. 10G- 258) The present invention relates to devices having a movable member actuated by a plurality of reciprocating type hydraulic motors connected to the movable member at spaced points and wherein it is necessary or desirable to have the movable member travel or move in a predetermined manner with respect to a stationary member or some predetermined reference plane.

One of the principal objects ot the invention is the provision of a novel and improved device, for example, a shear, platen press, press brake, etc., having a movable member of substantial size in at least one dimension actuated by a plurality of reciprocating type double acting hydraulic motors connected to the movable member at relatively widely spaced points and means for supplying pressure fluid to the respective motors in such a manner that the movable member is maintained in a relatively exact or precise predetermined relation or attitude, for example, parallel with or inclined at a predetermined angle, to a stationary blade or platen not only during the work and return strokes of the member but at other times, for example, during the period that the machine is at rest and/or during the decompression portion of the cycle of operation.

A specific object of the invention is the provision of a novel and improved metal bending press brake comprising an elongated ram movable towards and from a tool or die table or support by a pair of pressure liuid operated double acting reciprocating motors connected to the frame and to the ram at spaced points, discrete liuid pressure sources for the motors, tirst valve means selectively connecting one of the pressure lluid sources to the frame end of one of the motors and the other of the fluid pressure sources to the frame end of the other of the motors or one of the pressure fluid sources to the ram end of one of the motors and the other of the pressure fluid sources to the ram end of the other of the motors, and a pair of discrete conduit means connecting the fluid pressure sources to the lirst valve means, in combination with a supplemental liuid pressure source, second valve means selectively connecting the supplemental pressure fluid source to one or the other of the conduit means, a movable member operatively connected to the frame and the ram and movable in opposite directions from a neutral position in response to dellections in the frame and variations of the ram from a predetermined attitude relative to the tool support or table, lirst means operatively connected to the movable member for controlling actuaftion of the second valve means while the first valve means is in a position to connect the conduit means to lthe motors to connect the Asupplemental fluid pressure source to the conduit means connected to the lagging motor when the movable member moves a predetermined distance in either direction from the neutral position, second means operatively connected to the movable member for interrupting the pair of liuid pressure sources while the first valve means is in a position to connect the conduit means to the motors when the movable member moves a second predetermined distance in either direction from the neutral position a distance greater than the lirst predetermined distance, a third means operatively connected to the movable member for interrupting lall of the lluid pressure sources and ythe actuation of all of the valve means when the movable member moves a third predetermined distance in either direction from the neutral position a distance greater than the second predetermined distance, third valve means connected to the fluid pressure motors for effecting decompression thereof, and means for operating the third valve means and for preventing operation of the first valve means to reverse the ow of pressure lluid to the motors for a predetermined interval subsequent to operation thereof to disconnect the liuid pressure sources from the motors, characterized by a fourth valve means for selectively connecting the supplemental fluid pressure source to the ram ends of one or the other of the motors and means placing the fourth valve means during theaforesaid interval under the control of the lirst means operatively connected to the movable member whereby the supplemental fluid pressure source may be connected to the ram end of the leading motor during said interval while said movable member is `beyond said lirst predetermined distance or position.

The invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages will be apparent to those skilled in the art to which it relates from the following description of the preferred embodiment of the invention described with reference to the accompanying drawings forming a part of this specilication in which similar reference characters designate corresponding parts and in which:

FIG. l is a front elevational view of a sheet metal or plate bending brake or press embodying the present invention;

FIG. 2 is a diagrammatic view showing the hydraulic system and the mechanical part of the levelling control; and

FIGS. 3, 4 and 5 comprise a wiring diagram showing the electrical control for the press.

The present invention is especially applicable to bending presses or brakes and is herein shown as embodied in such a press. It is, however, to be understood that the invention is applicable to various types of presses and other machines utilizing multiple pressure fluid operated reciprocating type motors and the present showing is intended to be merely-illustrative of the invention and not to be restrictive in any manner.

Referring to the drawings, the press shown comprises a frame including stress-resisting, plate-like end members or sidehousings 13, 14 having aligned openings 15, 16 in their front edges; a combination reservoir and sump 17 interposed between and supported by the upper ends of the side housings 15, 16; and a table or die support 1S supported and lixedly secured to the top of a heavy plate or stationary blade 20 extending between and lixedly secured to the side housings 15, 16.

A movable ram or upper blade, designated generally by the reference character 25, located directly above the table or die support 18 is slidably supported by the side housings for linear movement towards and from the table or die support through power and return strokes. The lower edge of the ram 25 is adapted to carry a suitable punch or other tool.

The ram or movable blade 25 is adapted to be reciprocated towards and from the table or die support 18 by reciprocating type double acting hydraulic pressure motors 26, 27. The cylinders 30, 31 which are connected to the side housings 13, 14 of the press and the piston rods 32, 33 of which are connected by ball and socket connections or joints 34, 35 to opposite ends of the blade 25. Hydraulic liuid, preferably oil, for operating the hydraulic motors 26, 27 is supplied by two constant volurne unidirectional main high pressure pumps 36, 37 and two constant volume unidirectional auxiliary low pressure pumps 40, 41 driven by electric motors 42, 43 and a constant volume unidirectional leveling high pressure pump 44 driven by an electric motor 45. The high pressure pump 36 and the low pressure pump 40 are driven by the motor 42 and the pumps 37, 41 are driven by the motor 43. The pumps and motors as well as a number of the other parts of the hydraulic system are supported upon the top of the sump 17 which is in the form of an elongated rectangular hollow member extending between and connected to the upper end of the opposite end housings 13, 14.

Referring to the schematic hydraulic and electrical wiring diagrams, FIGS. 2-5 and assuming that the reciprocable blade 25 is in its raised position, the motors 42, 43, 45 are started by depressing the start push button switch 50. The depressing of the start push button switch 50 closes its normally open contacts 51, 52 and establishes a circuit from an input power line 53 through the normally closed contacts 54, 55 of stop push button switch 56, wire 57, now closed contacts 51, 52 of start push button switch 50, wire 58, operating solenoid 60 of rel-ay 61, wire 62, normally closed motor overload contacts 63, forming a part of the controller for the motor 42, wire 64, normally closed motor overload contacts 65 forming a part of controller for the motor 43, wire 66, and normally closed overload contacts 67 forming a part ofthe controller for the motor 45 to power line 68. The energization of relay 61 closes a pair of normally open contacts '70 which establish a holding circuit for the relay about the start push button switch 50, which may now be released. The energization of relay 61 also closes normally open contacts which energizes the operating solenoid of the motor starters for the motors 42, 43, 45. The relay 61 further includes normally open contacts 72, 73 which are closed upon the energization of its operating coil 60 to connect a control circuit including the wires 75, 76 to the power lines 53, 68.

The control circuit mentioned includes a two-position selector switch, designated generally by the reference character 80, through which different cycles of operation of the press brake can be selected. When the selector switch 80 is in the position shown in the wiring diagram, hereinafter referred to as the safety stroke or first position, the ram 25 of the press will move in a downwardly direction as long as the operator maintains his foot on the pedal switch 81 and will move upward when the operator releases the switch or the ram 25 will move downward until a down limit switch 82 is opened, at which Itime the ram will make the up stroke after decompression takes place even if the operator keeps his foot on the pedal switch. If the operator partially releases the pedal switch 81 to its mid position when the ram 25 is moving downwardly ram motion will stop. If the operator keeps his foot on the pedal switch 81 continuously the ram 25 will make successive down and up strokes until the operator releases the foot switch 81. When the selector switch 80 is in the second position, the ram 25 can be inched down by the operator depressing a manually operable push button switch 84 or by using of the pedal switch 81, or the ram can be inched up by the operator depressing the manually operable switch 85. The switches 84, 85, as well as the motor start and stop switches 50, 56 are on a control panel 86 located at a convenient place on the right hand side of the machine. 'I'hedown and up limit switches 82, 83 are connected to the right hand side of plate 14 just behind the right hand end of the ram 25 and are adapted to be operated by adjustable cams or trips connected to the rear right hand end of the ram. The down or up limit switch opens as the ram reaches the end of its down or up stroke, respectively. The switches reclose as soon as the ram begins to move in the opposite direction.

When the ram 25 is inoperative with the motors 42 and 43 running, the main high pressure pumps 36, 37 discharge to the sump 17 through the center position of three-position directional valves 87, 88 respectively. The pumps 36, 37 can also discharge to sump 17 through pressure controlled high pressure relief valves 90, 91 connected between their discharge conduits 92, 93, respectively, and the sump either at substantially zero pressure or at system pressure `as will be described subsequently.

The control cylinders of the relief valves 90, 91 are connected to a conduit 94 which in turn is connected by a check valve 95 to a conduit-96 leading to a two-position solenoid operated venting valve 97 normally spring biased to open position. The conduit 94 is also connected by a check valve 100 to a conduit 101 leading to a manually operable remote control two-position venting valve 102. The conduit 101 is also connected to tonnage control manually adjustable relief valve 103 and a pressure gauge 104.

When the venting valve 97 is closed the maximum pressure of the hydraulic fluid in the conduit 94 and in turn the relief valves 90, 91 is controlled by the tonnage control adjustable relief valve 103. This valve determines the pressure at which the pressure controlled relief valves 90, 91 open and can be adjusted to determine or regulate the maximum tonnage that can be exerted by the ram so as to prevent injury to the press and more particularly, to the side plates or frames 13, 14. A pressure gauge 104 connected to the conduit 101 through the manual vent valve 102 is preferably located adjacent to the adjustment for the tonnage control relief valve 103 and is preferably graduated in tons of pressure exerted by the ram 25.

The low pressure pumps 40, 41 connected to and driven by the motors 42, 43, respectively, normally discharge to the sump through the center position of the three-position directional valves 87, 88, respectively. The pumps 36, 37 can also discharge to sump 17 through pressure controlled low pressure relief valves 112, 113 connected between their discharge conduits 114, 115, respectively, and the sump either at substantially zero pressure or at system pressure as will be described subsequently. The low pressure relief valves 112, 113 are similar to the high pressure relief valves and the control cylinders thereof are connected to a conduit 116 which is in turn connected by a check valve 117 to a conduit 118 having connected thereto a pressure gauge 120, a two-position solenoid operated venting or dump valve 121 and a manually operated remote control two-position venting or dump valve 122. The pressure gauge and the valves 121, 122 are similar to the pressure gauge 104 and the valves 97, 103, respectively. and perform similar functions but with respect to the low pressure pumps 40, 41.

The leveling pump 44, driven by the electric motor 45, normally discharges to the sump through the center positions of three-position solenoid operated stroke attitude or leveling valves 124, non-stroke including decompression attitude or leveling valve 125 to which it is connected by a conduit 126, a pilot pressure sequence valve 127, a conduit 128, Valve 124, conduit 129, valve 125, conduit 130, lter 131 and sump conduit 132.

The leveling pump 44 can also discharge to the sump through a pressure controlled leveling pump relief valve 133 connected to the conduit 128. The control cylinder of the relief valve 133 is connected by a conduit 134 and a check valve 135 to the conduit 101 leading to the tonnage control valve 103. From the foregoing it will appear that the leveling pump relief valve 133 opens to discharge or dump the leveling pump to the sump when the manual venting or dump valve 102 is open or when the pressure exceeds the setting of the maximum tonnage relief valve 103. The pilot sequence valve prevents the pressure in the conduit 126 from dropping below that required to operate the pilot or control valves hereinafter referred to.

Referring more particularly to FIGURE 3, when the contacts 72, 73 of relay 61 closed their closing established a circuit for the operating solenoid 137 of relay 139 from the line S3 through the now closed contacts 72 of relay 61, wire 75, now closed contacts 148, 141 of maximum out of level limit switch 142, wire 143, normally closed contacts 144 of relay 145, wire 146, normally closed contacts 147 of relay 143, wire 156, operating solenoid 137 of relay 139, wire 76, now closed contact 73 of relay 61 to line l68. Relays 145, 148 are in the-leveling or attitude controls. Energization of the operating solenoid 137 of relay 139 closes its normally open contacts 151, 152. The contacts 151 of relay 1319 are in series circuit with the operating solenoid 153 of venting or dump valve 97 and the closing of these contacts establishes a circuit from the line 53 through the now closed contacts 151, wire 154, and operating solenoid 153 to line 68 thereby energizing the operating solenoid 153 to close the dump or Vent valve 97 and cause the high pressure pump relief valves 90, 91 to close. The high pressure pumps, however, discharge to the sump through the respective main three-position four-way directional valves 87, 88 by way of the check valves 155, 156 and Ithe conduits 157, 158 and 159, 160 respectively. The supplemental or leveling pump 44 discharges to the sump through the three-position four-way stroke attitude or leveling valve 124 and the decompression and nonstroke attitude or leveling valve 125, by way of the conduit 126, sequence valve 127, conduit 128, valve 124, conduit 129, valve 125, conduit 130, filter 131 and condu-it 132. The pressure in the conduit 126, however, never dro-ps below the setting of the pilot sequence valve 127.

The contacts 152 of relay 139 are in series circuit with now closed contacts 165, 166 of high speed advance limit switch 167 and operating solenoid 168 of low pressure vent valve 121. The closing of contacts 152 establishes a circuit from the line 53 through now closed contacts 165, 166 of limit switch 167, wire 169, now closed contacts 152, wire 170 and operating solenoid 168 of low pressure vent valve 121 to line 68. Energization of the operating solenoid 168 of venting valve 121 closes the valve causing the low pressure pump relief valves 112, 113 to close. The low pressure pumps, however, discharge through the check valves 171, 172 into the conduits 92, 93 connected to the high pressure pumps 36, 37, respectively, and with the discharge from the high pressure pump into the sump through the directional valves 87, 818 as previously explained.

The pedal switch 81 has three distinct operating positions. When the pedal switch 81 is in its normal released position contacts 173, 174 are closed and contacts 175, 176 land 177, 178 are open. When the operator depresses the pedal switch 81 all the way down contacts 173, 174 are open and contacts 175, 176 and 177, 178 are closed. The pedal switch 81 also has a mid-position where contacts 175, 176 are open and contacts 173, 174 and 177, 178 are closed.

With the selector switch 88 in its rst position, the ram 25 of the press will operate in a downwardly direction by the operator depressing the pedal switch 81 thereby closing its normally open contacts 177, 178 and 175, 176. The closing of the normally open contacts 177, 178 of the pedal switch 81 establishes a circuit from the power line 53 through the now closed contacts 72 of relay 61, wire 75, normally closed contacts 140, 141 of maximum out of level switch 142, wire 143, now closed contacts 177, 178 of pedal switch 81, wire 180, normally closed contacts 181 of relay 182, normally closed contacts 183 of relay 139, wire 184, operating solenoid 185 of timing relay 18,6, line 716, now closed contacts '73 of relay 61 to line 68. The contacts 187, 188 of timing relay 186 open instantaneously Kand close after a time delay when operating solenoid 1815 of timing relay 186 is deenergized. The open-ing of contacts 187, 188 prevents the operating solenoid 198 of ram up or press open relay 182 from being energized, while the ram is on the down stroke and for a predetermined time interval subsequent to the interruption of any downward movement ot vthe ram while decompression of ythe hydraulic system is taking place. The closing of the normally open contacts 175, 176 of the pedal switch 81 establishes a circuit from the power line 53 through the now closed contacts 72 of relay 61, wire 75, normally closed contacts 140, 141 of maximum out of level switch 142, wire 143, now closed contacts 175, 176 of pedal switch 81, wire 191, normally closed contacts 192, 193 of down limit switch 82, wire 154, normally closed contacts 195 of relay 196, wire 197, normaliy closed contacts 198 of relay 182, wire 199, operating solenoid 260 of ram down or press close relay 201, wire 76, and now closed contacts 73 of relay 61 to line 68. The energization of the operating solenoid 286 of down relay 201 closes its normally open contacts 282, 283, 284, 2G15, 207, 288, and opens its normally closed contacts 218. The closing of contacts 282 establishes a circuit for the operating solenoid of instantopen-delayed-closing decompression timer relay 186 from the wire 53 through the now closed contacts 72 of relay 61, wire 75, now closed contacts 140, 141 of maximum out of level switch 142, wire 143, now closed contacts 202 of relay 281, wire 184, operating solenoid 185 of relay Wire 186, wire 76, and now closed contacts 73 of relay 61, to Wire 67. The timing relay was already energized, however, so no new operation takes place at this time.

.T he contacts 283, 204 of relay 201 are in series circuit with the operating solenoids 223, 224, respectively, for the stroke leveling valve 124 which vaive controls the leveling of the ram, and the closing of these contacts conditions circuits for subsequent operation in the event the ram gets out of level.

The closing of the normally open contacts 2G15 of relay 261 establishes a circuit for the operating solenoid 226 of the normally open decompression valve 227 from the line 53 through the now closed contacts 20.5, wire 184 and operating solenoid 226 of decompression valve 227 to line 68. The energization of operating solenoid 226 of decompression valve 227 closes the valve.

The closing of the normally open contacts 287 of relay 201 establishes a circuit from the line 53 through the now closed contacts 2417, wire 230, down solenoid 231 of three-position tour-way direction control valve 232 t0 line 68. Energization of the operating solenoid 231 of control valve 232 shifts the valve to the left as viewed in FIG. 2 connecting the high pressure control conduit 131 leading to the leveling pump 44 to the conduit 233 leading to the control cylinder 234 of the three-position four-way main direction valves 87, 88 which are mcchanically interlocked by an adjustable member 235 so that they operate together, to shift the control valves 87, 88 to the left as viewed in FIG. 2 thereby lconnecting the conduits 157, 158 to the conduits 236, 237 which conduits are in turn connected to the upper end of the cylinders 30, 31 of the uid pressure motor 26, 27, re-

spectively, thus connecting the high pressure and 10W pressure pumps 36, 40 and 37, 41 with the upper end of the uid pressure motors 26, 27, respectively, causing the pistons and piston rods thereof to move the left and right hand ends of the ram in a downwardly direction. The opposite control cylinder 238 is simultaneously connected to the sump through the conduit 240, the valve 232 and the lconduit 241.

The fact that the low pressure vent or dump valve 121 is closed results in the low pressure pumps 40, 41 pumping into the conduits 92, 93 and the upper ends of the cylinders 38, 31 of the hydraulic motors 26, 27 until the ram 25 has moved in a downwardly direction a suicient distance to cause limit switch 167 to trip, opening the circuit to operating solenoid 168 of vent or dump valve 121. The spring of the valve 121 opens the valve thereby venting or opening the low pressure relief valVeS 112, 113 allowing the low pressure pumps 4t), 41 t0 dump their output to sump at substantially zero pressure. This results in a high speed approach of the ram to working position since each cylinder is being supplied by both a high pressure pump and a low pressure pump. The check valves 170, 171 interposed between the conduits 92, 93 and 114, 115, respectively, prevents the high pressure pumps 36, 37 from pumping into the conduits 114, 115 when the pressure in the cylinders 30, 31 exceeds the setting for the low pressure relief valves 112, 113, or when the low pressure pumps 40, 41 are dumping their output to sump at substantially zero pressure.

The normally open contacts 208 of relay 201 are in series circuit with the operating solenoid 250 of a cornbination rapid advance and high speed pressure stroke two-position four-way control valve 251 and normally closed contacts 252, 253 of the high speed approach limit switch 167 which switch is held closed by an elongated adjustable cam on the ram during a predetermined movement of the ram and which cam allows the normally closed contacts of the switch to open after a predetermined movement of the ram in a downwardly direction. The closing of the normally open contacts 208 of relay 201 therefore establishes a circuit from the line 53 through the now closed contacts 208, wire 255, now closed contacts 252, 253 of switch 167, wire 256, and operating solenoid 250 of control valve 251 to the line 68. Energization of the operating solenoid 250 of control valve 251 shifts the valve to the left as viewed in y FIG. 2 thereby connecting the sump conduit 258 to a conduit 260 leading to the cylinders 261, 262 of hydraulically operated check valves 263, 264 allowing the seating of the check valve balls and blocking the flow of oil through the check valves 263, 264 in the direction in which the valves normally block the oil from tlowing.

The blocking action of the right hand check valve 263 connects the lower end of the cylinder 31 of the left hand fluid pressure operated motor 27, which had previously been connected to the sump by way of the conduit 265, pressure counter-balancing valve 266, conduit 267, hydraulically operated check valve 263, conduit 263, valve 87 and conduit 159, to the upper end of cylinder 30 by way of conduit 267, check valve 270, conduit 157, valve S7 and conduit 236. The blocking action of the left hand hydrauliclly operated check valve 264 connects the lower end of the cylinder 30 of the left hand motor 26 which had previously been connected to the sump by `way of conduit 271, pressure counterbalancing valve 272,

conduit 273, check valve 264, conduit 274, valve 88 and conduit 160, to the upper end of cylinder 27 by way of conduit 271, pressure counterbalancing valve 272, conduit 273, check valve 275, conduit 158, valve 8S and conduit 237. The connecting of the lower ends of the cylinders 30, 31 of the motors 26, 27, with the upper end of the opposite cylinder gives a still further rapid advance to the ram 25 until the switch 167 is permitted by its operating cam to open its normally closed contacts 252, 253 and the switch 280 is open denergizing the operating solenoid 250 of the control valve 251 thereby allowing the valve, which is spring biased to its iirst or normal position, to return thereto and reconnect the control conduit 260 to the control line 126. This returns hydraulically operated check valves 263, 264 to free iloW position since the balls of the check valves are unseated by pressure Huid allowing free flow in the direction in which the valves normally block oil from flowing and reconnects the lower ends of the cylinders of the motors 26, 27 to the sump through the conduits 271, 265, counterbalancing valves 272, 266, conduits 273, 267, hydraulically operated check valves 264, '263, conduits 274,

268, the main directional valves SS, 87 which are now into their left hand position, and conduits 160, 159, respectively. During the up stroke the opening or closing of contacts 165, 166 of switch 167 has no elfe/ct since the contact 278 of up relay 182 will be closed keeping solenoid 168 of vent or dump valve 121 energized thereby keeping low pressure pumps 40, 41 pumping into the bottom ends of ycylinders 30, 31. The counterbalancing 75 valves 272, 266 are adjustable andopen upon the attaining of a desired pressure in the lower ends of the cylinders 30, 31, respectively. These valves are normally set so as to maintain the ram 25 in any position in which it is stopped or at its top position, that is, at the end of its up stroke when the press is not operating.

Provision is made in a form of an on-off manually operated selector switch 280 in parallel circuit with the contacts 252, 253 of the cam controlled high speed or rapid advance switch 167 for maintaining the circiut to the operating solenoid 250 of rapid advance valve 251 and in turn the connection between the lower and upper ends of the cylinders 30, 31, subsequent to the opening of the contacts 252, 253 of switch 167 to increase the Speed of the working portion of the stroke when this switch is closed. The maximum pressure obtainable, however, under these conditions will be decreased to approximately one-half of that otherwise available.

The normally closed contacts 210 of relay 201 are in series circuit with the operating solenoids 281, 282 of decompression leveling valve and the opening thereof assures that this valve will not operate but will remain in its normal or central position during downward operation of the ram 25.

The ram 25 continues its downwardly movement until the operator releases the pedal operated switch 81 to open contacts 175, 176, until the load is such that the ram will not move further in the downward direction, or until the down limit switch 82 is operated to open its normally closed contacts 192, 193. The third mentioned condition usually prevails when the press is used to perform bending operations wherein the work is bottomed in the die by the punch. This switch is opened by an adjustable carn or trip on the ram 25 when the ram has reached a predetermined closed or down position to open the circuit for the down relay 201, thereby allowing its normally open contacts 202, 203, 204, 205, 207, 208 to reopen and its normally closed contacts 210 to reclose.

As down limit switch 82 opens its contacts 192, 193 and closes its contacts 285, 286, solenoid 287 of relay 196 is energized, a circuit being formed from line 53 through contacts 72 of relay 61, wire 75, contacts 140, 141 of maximum out of level limit switch 142, wire 143, contacts 175, 176 of pedal switch 81, wire 191, contacts 285, 236 of down limit switch 82, wire 290, solenoid 287 of relay 196, wire 76, contact 73 of relay 61 to line 68. When relay 196 is energized it establishes its own holding circuit by means of its normally open contacts 291 from wire 143 through the normally closed contacts 292 of relay 182, wire 293, now closed contact 291 of relay 196, wire 290, solenoid 287 of relay 196 to wire 76. The normally closed contacts of relay 196 open in the down relay 201 circuit. This prevents the down relay 201 from being reenergized if the limit switch contacts 192, 193 should reclose due to frame deliection, etc.

The reopening of contacts 203, 204 of relay 201 at this time does not produce any operation since these contacts are in the stroke leveling control circuits. If the manually operable selector switch 280 is in its on position the lower ends of the cylinder of the uid pressure operated motors 26, 27 will be connected to the upper ends thereof through the check valves 275, 270 when the contacts 208 of relay 201 open. This will deenergize the operating solenoid 250 of the control valve 251 for the hydraulically operated check valves 263, 264 and allow the control valve 251 and in turn the check valves 263, 264 to return to their free How positions and connect the lower ends of the cylinders 30, 31 of the Huid pressure operated motors 26, 27 to the sump.

The reopening of contacts 207 of the relay 201 allows the direction control valve 232 which is spring biased to its central position to return to its central position thereby connecting the control conduit 233, to conduit 241leading to the sump which in turn permits the main directional valves 87, 08 which are alsospring biased to their central position to return thereto disconnecting the upper ends of the cylinders 30, 31 of the fluid pressure operated motors 26, 27 from the supply conduits 157, 158 and blocking their connections with the control valves 87, 88, respectively. The return of the direction control valves 87, 88 to their central inoperative positions reconnects the supply conduits 157, 158 to the conduit 159, 168 leading to the sump.

The opening of the contacts 205 of the relay 201 breaks the operating circuit for the solenoid 226 of the decompression valve 227 allowing the valve which is spring biased `to its inoperative or neutral position to return thereto thereby reconnecting the conduits 302, 303 connected to conduits 236, 237 by check valves 304, 305 to conduits 306, 307 leading to the sump. These latter conduits, however, are restricted so that the pressure in the system is gradually reduced.

The reopening of the contacts 202 deenergizes the operating solenoid 185 of the decompression timer 186 allowing, after a predetermined time delay, its normally closed contacts 187, 188 to reclose.

The reclosing of the normally closed contacts 187, 188 of the decompression timer relay establishes a circuit for the operating solenoid 190 of relay 182 from the line 53 through the now closed contacts 72 of relay 61, wire 75, now normally closed contacts 140, 141 of maximum out of balance limit switch 142, wire 143, normally closed contacts 173, 174 of pedal switch 81 which is now released, wire 312, now closed contacts 313, 314 of selector switch 80, wire 315, normally closed contacts 316, 317 of reset ram level switch 318, wire 320, now closed contacts 321, 322 of up limit switch 83, wire 323, now closed contacts 187, 188 of relay 186, wire 324, operating solenoid 190 of relay 182, wire 76, now closed contacts 73 of relay 61 to line 68.

The energization of the operating solenoid 190 of relay 182 opens its normally closed contacts 292, 198, 330, 181 and closes its normally open contacts 278, 331, 332, 333 and 334. Contacts 198 are in series circuit with the operating solenoid 208 of relay 201 the energization of which is necessary to move the ram 25 in a downwardly direction and the opening of these contacts assure deenergization of relay 201 during the return or upward movement of `the ram.

The opening of contacts 330 which are in series circuit with contacts 210 of relay 281 and the operating solenoids 281, 282 of decompression leveling valve 125 assures that this valve will remain in its normal position during upward movement of the ram 25. Contacts 332, 333 are in the leveling control and will be hereinafter referred to.

Contacts 332, 333 of relay 182 are in series circuit with the operating solenoids 223, 224 respectively, of the stroke leveling valve 124 and their closing conditions circuits which operate in the event the ram 25 gets out of level.

The closing of contacts 334 of relay 182 establishes a circuit from the line 53, through now closed contacts 334, wire 335, up solenoid 339 of three-position fourway direction control valve 232 to line 68. The energization of the operating solenoid 339 of control valve 232 shifts the valve to the right as viewed in FiG. 2 connecting the high pressure control conduit 126 leading to the leveling pump 44 to the conduit 240 leading to the control cylinder 238 of the three-position four-way main direction valves 87, 88 which, as previously explained, are mechanically interlocked by an adjustable member 235 so that they operate together, to shift the control valves 87, 88 to the right as viewed in FIG. 2 thereby connecting the conduits 157, 158 to the conduits 268, 274 which conduits are in turn connected by way of the hydraulicaily operated check valves 263, 264 and the conduits 267, 273, check valves 336, 337, and conduits 265, 271 to the lower end o-f the cylinders 31, 30 of the uid pressure motor 27, 26, respectively, thus connecting the high pressure and low pressure pumps 36, 40 and 37, 41 with the lower end of the uid pressure motors 27, 26 respectively, causing the pistons and piston rod thereof to move the right and left hand ends of the ram in an upwardly direction. The opposite control cylinder 234 is simultaneously connected to the sump through the conduit 233, the valve 232 and the conduit 241. Attention is called to the fact that the pumps are cross connected to the motors 26, 27 during the return or up stroke of the ram, as compared to their connections during the down stroke.

The low pressure vent or dump valve 121 is preferably energized during the up or return stroke therefore the low pressure pump 40, 41 are pumping into the motor supply conduits 92, 93 and the return of the ram is effected by the high pressure pumps 36, 37 and the low pressure pumps 40, 41. The rapid up movement is accomplished throughout `the entire return stroke by placing normally open contacts 278 of relay 182 in parallel circuit with contacts 165, 166 of rapid advance limit switch 167.

The ram 25 continues to move in an upwardly direction until the up limit switch 83 is opened by its trip or cam. After the down limit switch 82 is tripped the ram will move upward whether the operator releases the foot switch or not. The opening of contacts 32,1, 322 of up limit switch 83 deenergizes the operating solenoid 198 of relay 182 and allows its normally closed contacts 292, 198, 330, 181 to reclose and its normally open contacts 278, 3311, 332, 333 and 334 -to reopen. The closing of contacts 198 conditions the circuit to relay 201 for subsequent operation of the ram 25 in a downward direction.

The reopening of contacts 334, of the relay 182 allows the three-position four-way direction control valve 232, which is spring biased, to its central position to return to its central position thereby connecting the control conduit 240 to conduit 241 leading to the sump which in turn permits the three-position four-way main directional valves 87, 88 which are also spring biased to their central posi- -tion to return thereto disconnecting the lower ends of the cylinder 30, 31 of the fluid pressure operated motors 26, 27 from the supply conduits 157, 158 and connecting them to the conduits 159, leading to the sump. Simultaneously the conduits 236, 237 are blocked at their connections with the control valves 87, 88 respectively. The return of the direction control valves 87, 88 to their central inoperative positions also reconnects the supply conduits 157, 158 to the conduit 159, 160 leading to the sump.

In addition to the pedal switch operation as described above, the pedal switch 81 has an intermediate position that allows the operator to stop down motion of the ram 25 without initiating upward motion of the ram. In the intermediate position the pedal switch 81 contacts 173, 174 and 177, 178 are closed and the contacts 175, 176 are open. Since contacts 175, 176 are in series circuit with down relay 281 this relay is deenergized and down motion ofthe ram is stopped, as previously described. Up motion is not initiated, however, since contacts 177, 178 of pedal switch 81 keep the solenoid 185 of timerl relay 186 energized thereby maintaining contacts 187, 188 of timer relay 186 open keeping the solenoid 190 of up relay 182 deenergized. The timing relay 186 is energized when a circuit is completed from line 53 through contact 72 of relay 61, wire 75, contacts 140, 141 of maximum out of level limit switch 142, wire 143, contacts 177, 178 of pedal switch 81, line 180, normally closed contact 1811 of up relay 182, wire 340, normally closed contact 183 of relay 196, line 184, solenoid 185 of timing relay 186, line 76, contact 73 of relay 61 to line 68.

The ram 25 can be made to stroke down and up continuously by keeping the pedal switch depressed. As previously described, down motion stops when contacts 192, 193 of down limit switch 82 open, thereby deenergizing the down relay 201 and energizing the relay 196 causing the normally closed contacts 183 of relay 196 to open 1 1 thereby deenergizing timing relay 186 closing the contacts 187, 188 of timing relay 186 after a time delay which allows decompression of the hydraulic fluid in the system. A circuit for the up relay 182 is completed from line 53, through contacts 72 of relay 61, wire 75, contacts 140, 141 of maximum out of level limit switch 142, line 143, normally closed contacts 341 of down relay 201, wire 312, contacts 313, 314 of selector switch 80, wire 315, contacts 316, 317 of push button 318, wire 320, now closed contacts 321, 322 of up limit switch 83, wire 323, now closed contacts 187, 188 of timing relay 186, wire 324, solenoid 190 of relay 182, wire 76, contact 73 of relay 61 to line 68. The ram then moves upward as previously described until the up limit switch 83 opens its contacts 321, 322 deenergizing the up relay 182 stopping upward movement of the ram. When the ram started upward the vdown limit switch 82 returned to its normal condition so when the up relay 182 is deenergized at the upper limit of ram travel and the operator still has the pedal switch depressed a circuit for down relay 201 will be completed from line 53, through contacts 72 of relay 61, wire 75, contacts 140, 141 of maximum out of level limit switch 142, line 143, contacts 175, 176 of pedal switch 81, wire 191, contacts 192, 193 of down limit switch 82, wire 194, normally closed contact 195 of relay 196, wire 197, normally closed contact 198 of relay 182, wire 199, solenoid 200 of relay 201, wire 76, contact 73 of relay 61 to line 68. The ram 25 then moves downward as previously de scribed. This cycle will be repeated as long as the opera- -tor keeps the pedal switch 81 depressed.

With the selector switch 80 in the other of its two operating positions from the position shown in the drawings, that is with its contacts 342, 343 and 344, 314 closed, the press can be manually operated to inch or move the ram 25 do-wn or up by depressing the down or up push button switches 84 and 85, respectively. The normally open contacts 345, 346 of the down push button switch 84 are in series circuit with the contacts 342, 343 of selector switch 80 and both sets Vof contacts are in parallel circuit with the normally open contacts 175, 176 of pedal switch 81 between the wires 143 and 191. From this it follows that the operation of the press is the same as previously described with respect to the movement of the ram 25 in a downwardly direction when the selector switch 80 in its last mentioned position regardless of whether the pedal switch 81 is operated to close its normally open contacts 175, 176 or the push button 84 is operated to close its normally open contacts 345, 346.

The normally open contacts 347, 348 of the up push button switch 85 are in series circuit with the normally open, but now closed, contacts 342, 343 and 344, 314 of selector switch 80 and the three sets of contacts are in parallel circuit between the wires 143, 315, with the normally closed contacts 173, 174 of the pedal switch 81. With the selector switch 80 in its second or manual position, that is, in the position other than that shown in the wiring diagram the operating solenoid 190 of relay 182 will be energized and maintained energized so long as the up push button switch 85 is depressed or until the up limit switch 83 opens. As previously mentioned, after any movement of the ram 25 in a downwardly direction the ram can not be moved in an upwardly direction until after the decompression timer relay 186 has closed, but after the ram has been moved upwardly any amount, subsequent upward movements of the ram can be effected instantaneously assuming that the ram has not been moved in a downwardly direction between the upward movements.

It will be apparent that as a press operation is performed, one end of the ram or blade 25 may lead the other because the pumps connected to the respective hydraulic motors 26, 27 may not pump exact amounts of oil and/or the load or resistance to movement of the ram or blade may not be uniformly distributed between `the two motors 26, 27. In most instances, it is desirable to have the movable blade and the punch or punches carried thereby remain at a constant angle with respect to the table 18 and the die or dies carried thereby throughout the operation and the present press incorporates means for controlling the ow of pressure fluid to the respective hydraulic motors 26, 27 in such a manner that they move at a uniform speed regardless of the resistance encountered, etc.

This mechanism is herein referred to as the blade attitude or leveling control and includes a blade attitude sensing mechanism comprising an electric bridge designated generally as B and located in the housing 370 at the right hand end of the press. The bridge produces a signal when the blade is out of attitude or level which is conducted or fed into a circuit which changes the amount of or stops the flow of pressure uid to the respective motors in accordance to the signal, to restore the ram 25 to its predetermined position or attitude relative to the die table 18.

The attitude sensing mechanism shown comprises an electric bridge means, see FIGS. 2 and 5, including H- shaped armature 371 made of magnetic material and an electric coil surrounding each of the respective arms of the armature. The coils are designated 372, 373, 374, 375 and are connected to the alternating current power supply lines 53, 68 in such a manner that they form an electric reactance bridge similar to a Wheatstone bridge. The coils 372-375 are lixed to the frame of the press, in the present instance to the right-hand side housing 14, and the armature 371 is slidably supported by the housing for movement in a generally horizontal direction parallel with the length of the respective arms or cores thereof. The armature 371 is biased towards the rear of the press by a tension spring 376 connected thereto and to a pin 377 connected to the side housing 14 of the press and is adapted to be moved towards the front of the press by a relatively non-elastic, exible steel band 380 connected thereto and extending in a forwardly direction from the armature, that is, in a direction opposite to the spring 376. From the armature 371 the flexible steel band 380 passes about a sheave or pulley 381 xed to the frame member 14 above the throat 16 and then about a sheave 382 xed to the rear side of the right hand end of the movable ram 25.

From the sheave 382 the flexible band extends generally horizontally across the rear of the ram 25 and passes over a sheave 383 connected to the left-hand end of the ram 25 which extends to the outside of the left-hand side plate 13. From the sheave 383 the exible steel 'band extends downwardly in a generally vertical direction and has its end secured to the upper end of a member 384 adjustably connected to a member 385 which latter member is in turn connected to the side housing 13 above the throat 15. The member 384 projects through the member 385 and the lower end thereof is threaded and provided with a knurled narrow nut which facilitates adjustment of the member 384 relative to the member 385 and in turn the position of the H frame 371 in the bridge solenoids 382-385. By adjustment of the member 384, the armature 371 can be adjusted relative to the coils 372-375 to a neutral position in which the electric bridge is in balance, etc.

From the foregoing it will be apparent that with the electric bridge in balance at the beginning of the shearing operation any variation or change in the attitude or level of the ram 25 with reference to the die table 18 will cause the armature 371 to move to one side or the other of its neutral position and a signal to appear across its terminals 387, 388 of the bridge circuit. The magnitude and polarity of the signal will be a function of the blade out of attitude or balance. This signal is applied to two amplifying circuits comprising pairs of thyratron tubes 391i, 391 and 392, 393, respectively. The first circuit responds to a small out of balance condition to cause additional oil to be pumped by the auxiliary or balancing 13 pump 44 to the trailing hydraulic motor. If the out of 'balance condition exceeds that which can be taken care of by the auxiliary pump 44 the second circuit causes the vent valve 97 to open and the main pumps to be temporarily rendered ineiective to supply oil to the hydraulic motors 26, 27.

As the armature 371 moves in opposite directions from its neutral position the voltages across the bridge terminals 387, 388 will be 180 out of phase with the iirst. The change of phase indicates or senses which end of the ram is lagging and the magnitude of the output voltage ofthe bridge circuit indicates or senses the amount that the ram is out of attitude or level. The voltage impressed upon the bridge circuit is that of the voltage of the supply source since the bridge is directly connected to the lines 53, 68, which supply alternating current. The voltage impressed upon the plate circuits of the thyratron tubes 390, 391 and 392, 393 comes from opposite sides of a mid-tapped secondary 394 of a transformer 1395. The voltage impressed upon the plates of tubes 390, 392 will be 180 out of phase with the voltage impressed upon the tubes 391, 393. When an output voltage appears across the terminals 387, 383 of the bridge circuit, this voltage will be essentially in phase with the plate voltage with one of the tubes of each set 390, 391 and 392, 393 and out of phase with the plate Voltage of the other tube of the set. The bridge voltage is impressed upon the grids of both tubes of each set and the tubes in Which the voltages are in phase will conduct if the bridge signal is of predetermined values. The sensitivity of the respective pairs of tube circuits is controllable by adjusting the rheostats 396, 397 in the output of a full wave rectifier indicated generally by the reference character R which supplies the negative bias to the tubes 390-393.

The rheostat 396 is in the rst stage circuit including the tubes 390, 391 and controls the tirst stage circuit, and the rheostat 397 is in the second stage circuit which includes the tubes 392, 393. A transformer 398 is used to isolate the signals. The rheostats 396, 397 control the amount of negative grid bias applied to their respective tubes thus providing a sensitivity control since the greater the grid bias is the greater must be the Voltage appearing across the bridge terminals to cause the tubes to become conductive. This means that the greater the negative bias the further the ram 25 must be out of level before the tube circuits operate to bring the ram back to level condition. As previously suggested the second stage negative grid bias is normally adjusted higher than that of the first stage so that the operation of the rst and second circuits is progressive as the out-of-balance condition of the ram B increases. The grid circuits of the latter are connected to the bridge terminals.

The plate circuits of the tubes 390, 391 are connected to operating solenoids 400, 401 of relays 402, 403 having normally open contacts 404, 405 in series circuit with operating solenoids 223, 224 and 231, 282 of solenoid operated three-Way stroke balancing or attitude valve 124 and decompression and non-stroke leveling valve 125 which are selectively operable to connect the pressure iiuid supply lines 126 from the balancing or leveling pump 44 to the conduits 157, 158 leading from the main pumps to the directional valves 07, 88, and to the conduits 265, 271 connected to the lower end of the hydraulic motors 27, 26 respectively. The contacts 404 of relay 402 are in series circuit between the wire 143 and the supply line 68 with contacts 203 of down relay 201 and the operating solenoid 223 of stroke leveling valve 124 and contacts 405 are in series circuit between the wire 143 and the supply line 68 with contacts 204 of down relay 201 and operating solenoid 224 of stroke leveling valve 124. Normally open contacts 332 of up relay 182 are in parallel circuit With contacts 203 of down relay 201 and contacts 333 of up relay 182 are in parallel. circuit with contacts 204 of down relay 201 from which it follows that contacts 404 of relay 402 and contacts 405 of relay 403 are in series circuit with the operating solenoids 223, 224 of stroke leveling valve 124, rcspectively during the down and up stroke of the ram 25.

Assuming that the ram 25 is moving down, that the hydraulic motor 26 is lagging behind motor 27 thereby shifting the armature 371 of the bridge B to produce a signal on the grid of tube 390 in phase with the plate voltage of the tube and of sufficient amplitude to tire the tube, then, in this event relay 402 is operated to close its normally open contacts 404. The closing of contacts 404 of relay 402 energizes operating solenoid 223 of stroke leveling valve 124 thereby shifting the valve to the right as viewed in FIG. 2 to connect the pressure uid conduit 126 leading from the leveling pump 44 to conduit 157 which is now supplying pressure luid to the left-hand motor 26. The signal regains control of the tube 390 after each half cycle and as long as a positive signal in excess of the predetermined amount remains on the grid circuit of tube 390, the flow of pressure fluid to motor 26 from the main pump 36 will be supplemented by pressure fluid from the leveling or auxiliary pump 44. As soon as the left hand end of the ram 25 catches up with the right hand end the positive bias disappears from the grid of tube 390, relay 402 opens and stroke leveling valve 124 returns to its central position disconnecting the pump 44 from conduit 157. When the hydraulic motor 27 lags the motor 26, a signal in phase with the plate voltage of tube 391 will appear on the grid of tube 391 and if of suicient magnitude to tire the tube, relay 403 will be operated energizing solenoid 224 of stroke leveling valve 124 causing the auxiliary pump 44 to pump oil into the conduit 153 supplying oil from the main pump 37 to the motor 27 in a manner similar to that described with respect to motor 26.

1f the out of balance condition cannot be corrected by the balancing pump 44 and increases to an amount sufcient to move the armature 375 to a second predetermined position at either side of its neutral position, that is, to a position to raise the in phase signal on the grid of one of the tubes 392, 393, depending upon whether the left-hand motor 26 or the right-hand motor 27 is lagging the other, respectively, the tube tires or conducts energizing the selected one of the relays 145, 148 to open normally closed contacts 144 or 147, respectively, in series circuit with the operating solenoid 137 of relay 139. rl`his deenergizes the relay causing its normally open contacts 151, 152 to reopen deenergizing the operating solenoids 153, 168 of the high and lower pressure vent or dump valves 97, 121, respectively, allowing the valves to open thereby venting the relief valves 90, 91, 112, 113 discontinuing the main fluid pressure sources, that is, the flow of oil from the main high pressure pumps 36, 37, and the low pressure pumps 40, 41 if they are operating, to the motors 26, 27 but continuing the flow of oil from the auxiliary pump 44 to the lagging motor.

As the ram 25 reapproaches its level condition the second stage tubes 392, 393 and the rst stage tubes 390, 391 become inoperative in that order.

If, for some reason, the second stage leveling circuit does not operate etc., and either end of the ram 25 leads the other at any time a predetermined amount in excess of the amount required to tire the second stage tubes 392, 393, that is, to a third position at one or the other sides of its neutral position, the maximum out of balance limit switch 142 will be operated by a cam 408 on the armature 371 to open its normally closed contacts 140, 141 and stop the press and close its normally open contacts 410, 411. The level of the ram 25 can then be manually reset by the operator by depressing the reset push button switch 318 to open its normally closed contacts 316, 317 and closes its normally open contacts 412, 413 and 414, 415. The opening of the normally closed contacts 316, 317 renders the pedal switch 81 and the manual down and up switches S4, 85 inoperative, even though contacts 330 of up relay 182 subsequently close reenergizing wire 143.

The closing of contacts 412, 413 of reset push button 318 establishes, subsequent to decompression, and the reclosing of contacts 187, 188 of decompression timer 186, a circuit for the up relay 182 from the line 53 through now closed contacts 72, wire 75, now closed contacts 410, 411 of maximum out of attitude switch 142, wire 416, now closed contacts 412, 413 of reset switch 318, wire 323 now closed contacts 187, 188 of decompression timer 186, wire 324, operating solenoid 190 of up relay 182 to wire 76 and through now closed contacts 73 of relay 61 to line 68.

Energization of operating solenoid 190 of relay 182 opens its normally closed contacts 181, 198, 292, 330 and closes its normally open contacts 278, 331, 332, 333, 334. Contact 198 is an interlock contact in series circuit with the operating solenoid 200 of up relay 201 and contact 330 is an interlock Contact in series circuit with the operating solenoids 281, 282 of the decompression and non-stroke leveling valve 125. The closing of contacts 334 sets the directional control valve 232 in position for the blade to move up.

The closing of contacts 331 of relay 182 connects the wire 143 to the line 53 through the now closed contacts 72 of relay 61, wire 75, now closed contacts 410, 411 of maximum out of balance switch 142, wire 416, contacts 331 of relay 182, wire 420, now closed contacts 414, 415 of reset switch or push button 318 placing the stroke leveling valve 124 under the control of contacts 404, 405 of the first stage leveling relays 402, 403 respectively. One or the other of these contacts 404, 405 is closed depending upon which end of the ram is leading the other. The nid pressure motors 26, 27 are therefore connected to the supplemental or balancing pump 44 in a manner to restore the ram or blade 25 to the predetermined level or attitude.

As the blade or ram approaches the predetermined desired level or attitude the maximum out of balance or attitude switch 142 operates to reclose its normally closed contacts 140, 141 and reopen its normally open contacts 410, 411. This restores the control to the rst and second stage relays, etc., and the press continues to operate until it reaches the end of its upward stroke and the up limit switch 83 opens breaking the circuit for the operating solenoid 190 of up relay 182.

When the operating solenoid of the second stage balancing relays 145, 148 are deenergized the normally closed contact 144 or 147 thereof close and the upward movement of the blade continues under the operation of the high and low pressure pumps as well as the balancing pump until the desired attitude or level of the ram is restored whereupon the then operating rst stage balancing relay 402 o: 403 is deenergized. ln the event the selecting switch 80 is in the second of its two mentioned operative positions the upward movement of the ram stops upon the opening of the normally open contacts 410, 411 of the maximum out of attitude or level switch 142.

One of the features of the present invention is the fact that leveling is etfected during the decompression cycle of the press. This is necessary if the press is to reopen upon release of the pedal switch by the operator under certain unbalanced load conditions because of frame deflection. If for example the load is concentrated under the right hand motor 27, movement of the right hand end of the ram will stop as the load builds up. The left hand end of the ram, however, continues to move until the armature 375 has moved to its second predetermined position to the rear of its neutral position whereupon the uid pressure source for the left hand motor will be interrupted or disconnected. The blade 25 cannot move further out of level but the supplemental pump 44 will continue to supply iiuid pressure to the right hand motor which will shortly apply maximum tonnage to the load. As the tonnage builds up the right handend plate I14 will deect moving the pulleys 381, 382 further apart. As the distance between the pulleys 381, 382 increases the armature will be moved towards its neutral position but upon initiation of the decompression part of the cycle the frame will return to its non-deected or non-stressed condition allowing the pulleys 381, 382 to move towards one another and the armature to move towards the rear of the press. In some instances this movement of the armature is suicient to operate the maximum out of level switch 142 shutting down the press and preventing return of the ram except by use of the reset push button switch 318. Different operations and conditions exist when the load is concentrated under the left hand motor. In this event the armature 371 moves from its neutral position towards the front of the press incident to the operation of the stroke leveling feature of the press and moves back toward the neutral position with the relaxing of the frame incident to decompression.

Leveling during decompression is accomplished in the press shown by the three position four-way decompression and non-stroke leveling valve 125, the operating solenoids 281, 282 of which are under the control of the normall/ open contacts 404, 405 of the rst stage leveling relays 402, 403, respectively. In addition to being in series circuit with the contacts 404, 405, the operating solenoids 282, 283 of decompression leveling valve are in series circuit with interlock contacts 210 of up relay 201 and interlock contacts 330 of down relay 182 from which it follows that the decompression leveling valve 125 is under the control of the rst stage leveling relays 402, 403 during the period that decompression is taking place and at any time that the up relay 182 and down relay 201 are deenergized. When the ram is not operating and during the decompression part of the operating cycle, leveling is effected by connecting the supplernental pressure fluid source to the lower end of the motor connected to the lowest end of the ram 25 to raise the piston thereof and in this way level the ram 25. With the foregoing in mind and assuming that the motor 26 is connected to the lowest or leading end of the ram as would be the case in the event the load is concentrated under motor 27 as previously assumed the tube 390 is operating when the decompression part of the cycle begins, that is as the down stroke is completed. The operating solenoid 400 of relay 402 is therefore energized and its normally open contacts 404 closed. The closing of these contacts energizes the operating solenoid 281 of decompression leveling valve 125. The energization of the operating solenoid 281 of decompression valve 125 shifts the valve to the right as viewed in FIG. 2 thereby connecting the conduit 129, which is supplied with pressure fluid from the supplemental or leveling pump 44 through the conduit 126, sequence valve 127, conduit 128, stroke attitude or leveling valve 124, conduit 129, and non-stroke or decompression leveling valve 125 to the conduit 271 leading to the lower end of motor 26. In the event the motor 27 is connected to the lowest end of the ram, under similar conditions the non-stroke and decompression leveling valve 125 will be shifted in the opposite direction connecting the conduit 129 to the conduit 265 leading to the lower end of the motor 27. The conduits 271 and 265 have check valves 425, 426 therein which prevents the flow of fluid pressure from the lower ends of the motors 26, 27 to the decompression attitude or leveling valve 125.

It should also be noted that the decompression leveling valve 125 can level the ram when the pump motors 42, 43, 44 are on but the press is not being operated, that is, neither the down relay 201 nor the up relay 182 are energized. The solenoids 182, 183 of decompression leveling valve 125 will be under the direct iniluence of contacts 404, 405 of rst stage leveling relays 402, 403, respectively. Assuming the left hand motor 26 is connected to the lowest end of the ram 25 when the press is not being operated a circuit vwill be established from line 53 through now closed contact 72 of relay 61, wire 75, now closed contacts 140, 141 of maximum out of level limit switch 142, wire 143, contact 404 of relay 402, solenoid 281 of non-stroke and decompression leveling valve 125, normally closed contact 210 of down relay 201, wire 417, normally closed contacts 330 of up relay 182, wire 76 and contacts 73 of relay 61, to line 68. The operation of solenoid 281 of valve 125 shifts the valve to the right as viewed in FIG. 2 thereby connecting the conduit 129, to the conduit 271 leading to the lower end of motor 26. It can be seen, therefore, that if the ram should become out of level due to leakage through valves, etc., while the press is not being operated, valve 125 will cause the ram 25 to return to its level position.

From the foregoing it Will be apparent that the objects heretofore enumerated and others have been accomplished and that a novel and improved press has been provided having a ram movable by a plurality of pressure fluid operated motors connected thereto at relatively widely spaced points, extremely sensitive means including an electric bridge responsive to variations of the ram from a predetermined attitude relative to the die table or some other part of the press during the working and return stro-kes for temporarily supplementing the normal supply of uid to the lagging motor and in some events disconnecting the normal supply of tiuid to the lagging motor until the predetermined attitude is restored, regardless of the direction of movement of the ram and means for leveling the ram during the decompression part of the operating cycle of the press and during the time the press is not being operated but during which time the pump motors are on.

Having thus described our invention, what we claim is:

1. In a control system for an apparatus of the character described having a frame providing a supporting surface or table, an elongated first member movable towards and from the table, a pair of pressure tiuid operated double acting reciprocating motors connected to said frame and to said first member at spaced points for moving said first member towards and from said table and a pair of discrete uid pressure sources, iirst valve means for selectively connecting one of said pressure fluid sources to the frame end of one of said motors and the other of said uid pressure sources to the frame end of the other of said motors or one of said pressure fluid sources to the rst member end of one of said motors and the other of said pressure fluid sources to the first member end of the other of said motors, a pair of .discrete conduit means connecting said fluid pressure sources to said first valve means, a supplemental Huid pressure source, second valve means ,for selectively connecting said supplemental pressure fluid source to one or the other of said conduit means, a movable second member, means operatively connected to said frame and said first member and said movable second member for moving said movable second member in opposite directions from a neutral position in response to deections in said frame and variations of said first member from a predetermined attitude relative to said table, rst .means operatively connected to said movable second member for controlling actuation .of said second valve means while said first Valve means is in aposition to connect said conduit means to said motors to connect said supplemental fluid pressure `source to said conduit means connected to the lagging motor of said motors when .said movable second member moves a predetermined distance in either direction from said neutral position, second means operatively connected to said movable second member for interrupting said pair of uid pressure sources while said first valve means is in a position to connect said conduit means to said motors when said movable second member moves a second predetermined distance in either direction from said neutral position a distance greater than said first predetermined distance, a third means operatively connected to said movable second member for interrupting all of said duid pressure sources and the actuation of all of said valve means when saidY movable second member moves a third predetermined distance in either direction from said neutral position a distance greater than said second predetermined distance, third valve means connected to said fluid pressure motors for effecting decompression thereof, means for operating said third valve means and for preventing operation of said first valve means to reverse the flow of pressure fluid to said motors for a predetermined interval subsequent to operation thereof to disconnect said fluid pressure sources from said motors, fourth valve means for selectively connecting said supplemental uid pressure source to the first member ends of one or the other of said motors, and means placing said fourth valve means during said interval under the control of said first means operatively connected to said movable second member for controlling actuation of said fourth valve means whereby said supplemental fluid pressure source is connected to the first member end of the leading motor of said motors during said interval.

2. In a control system for an apparatus of the character described having a frame providing a supporting surface or table, an elongated first member movable towards and from the table, a pair of pressure iiuid operated double acting reciprocating motors connected to said frame and to said first member at spaced points for moving said rst member towards and from said table and a pair of discrete fiuid pressure sources, first valve means for selectively connecting one of said pressure fluid sources to the frame end of one of said motors and the other of said fluid pressure sources to the frame end of the other of said motors or one of said pressure fluid sources to the first member end of one of said motors and the other of said pressure fluid sources to the first member end of the other of said motors, a pair of discrete cond-uit means connecting said fluid pressure sources to said first valve means, a supplemental uid pressure source, second valve means for selectively connecting said supplemental pressure fluid source to one or the other of said conduit means,

a movable second member, means operatively connected to said frame and said first member and said movable second member for moving said movable second member in opposite directions from a neutral position in response to deiiections in said frame and variations of said first member from a predetermined attitude relative to said table, first means operatively connected to said movable second member for controlling actuation of said second valve means while said first valve means is in a position to connect said conduit means to said motors to connect said supplemental fluid pressure source to said conduit means connected to the lagging motor of said motors when said movable second member moves a predetermined distance in either direction from said neutral position, second means operatively connected to said movable second member for interrupting said pair of fluid pressure sources while said rst valve means is in a position to connect said conduit means to said motors when said movable second member moves a second predetermined distance in either direction from said neutral position a distance greater than said first predetermined distance, a third means operatively connected to `said movable second member for interrupting all of said fiuid pressure sources and the actuation of all of said valve means when said movable second member moves a third predetermined distance in either direction from ysaid neutral position a distance greater than said second predetermined' distance, third valve means connected to said fiuid pressure motors for effecting decompression thereof, means for operating said third valve means and for preventing operation of said first valve means to reverse ,the flow of pressure fluid to said motors for a predetermined interval subsequent to operation thereof to disconnect said uid pressure sources from said motors, fourth valve means for selectively connecting said supplemental uid pressure source to the first Vmember ends of one or the other of said motors, and means placing said fourth valve means during said interval and when said first member is not being operated up or down under the control of said first means operatively connected to said movable second member for controlling actuation of said fourth valve means whereby said supplemental fluid pressure source is connected to the first member end of the leading motor of said motors while said first member is not being operated up or down and including during said interval.

3. In a control system for an apparatus of the character described having a frame providing a supporting surface or table, an elongated first member movable towards and from the table, a pair of pressure fluid operated double acting reciprocating motors connected to said frame and to said first member at spaced points for moving said first member towards and from said table and a pair of discrete fluid pressure sources, rst valve means for 'selectively connecting one of said pressure fluid sources to the frame end of one of said motors and the other of said fluid pressure sources to the frame end of the other of said motors or one of said pressure fluid sources to the first member end of one of said motors and the other of said pressure fluid sources to the first member end of the other of said motors, a pair of discrete conduit means connecting said fluid pressure sources to said first valve means, a supplemental fluid pressure source, second valve means for selectively connecting said supplemental pressure fluid source to one or the other of said conduit means, an electric bridge means including two parallel circuits each comprising a plurality of electric impedance means, a movable second member forming a part of said bridge means, means operatively connected to said frame and said member and said first movable second member for varying the relative position of said second movable member in said electric bridge means and in turn the balance of said bridge means in response to deflections in said frame and variations of said first member from a predetermined attitude relative to said table, first means connected to said bridge means for controlling actuation of said second valve means while said first valve means is in a position to connect said conduit means to said motors to connect said supplemental fluid pressure source to said conduit means connected to the lagging motor of said motors when said movable second member moves a predetermined distance in either direction from a neutral position and thereby creating a first predetermined unbalance in said bridge means, second means connected to said bridge means for interrupting said pair of fluid pressure sources while said first valve means is in a position to connect said conduit means to said motors when said movable second member moves a second predetermined distance in either direction from said neutral position a distance greater than said first predetermined distance and thereby creating a second predetermined unbalance in said bridge means greater than said first predetermined unbalance, a third means controlled by said movable second member for interrupting all of said fluid pressure sources and the actuation of all of said valve means when said movable second member moves a third predetermined distance in either direction from said neutral position a distance greater than said second predetermined distance, a third valve means connected to said fluid pressure motors for effecting decompression thereof, means for operating said third valve means and for preventing operation of said first valve means to reverse the flow of pressure fluid to said motors for a predetermined interval subsequent to operation thereof to disconnect said fluid pressure sources from said motors, fourth valve means for selectively connecting said supplemental fluid pressure source to the first member ends of one or the other of said motors, and means placing said fourth valve means during said interval under the control of said first means connected to said bridge means for controlling actuation of said fourth valve means whereby said supmember end of the leading motor of said motors during said interval and while a predetermined unbalance exists in said bridge means in excess of said first predetermined unbalance.

4. In a control system for an apparatus of the character described having a frame providing a supporting surface or table, an elongated first member movable towards and from the table, a pair of pressure fluid operated double acting reciprocating motors connected to said frame and to said first member at spaced points for moving said first member towards and from said table and a pair of discrete fluid pressure sources, first valve means for selectively connecting one of said pressure fluid sources to the frame end of one of said motors and the other of said fluid pressure sources to the frame end of the other of said motors or one of said pressure fluid sources to the first member end of one of said motors and the other of said pressure fluid sources to the first member end of the other of said motors, a pair of discrete conduit means connecting said fluid pressure sources to said rst valve means, a supplemental fluid pressure source, second valve means for selectively connecting said supplemental pressure fluid source to one or the other of said conduit means, an electric bridge means including two parallel circuits each comprising a plurality of electric impedance means, a movable second member forming a part of said bridge means, means operatively connected to said frame and said first member and said movable second member for varying the relative position of said movable second member in said electric bridge means and in turn the balance of said bridge means in response to deflections in said frame and variations of said first member from a predetermined attitude relative to said table, first means connected to said bridge means for controlling actuation of said second valve means while said first valve means is in a position to connect said conduit means to said motors to connect said supplemental fluid pressure source to said conduit means connected to the lagging motor of said motors when said movable second member moves a predetermined distance in either direction from a neutral position and thereby creating a first predetermined unbalance in said bridge means, second means connected to said bridge means for interrupting said pair of fluid pressure sources while said first valve means is in a position to connect said conduit means to said motors when said movable second member moves a second predetermined distance in either direction from said neutral position a distance greater than said first predetermined distance and thereby creating a second predetermined unbalance in said bridge means greater than said first predetermined unbalance, a third means controlled by said movable second member for interrupting all of said fluid pressure sources and the actuation of all of said valve means when said movable second member moves a third predetermined distance in either direction from said neutral position a distance greater than said second predetermined distance, third valve means connected to said fluid pressure motors for effecting decompression thereof, means for operating said third valve means and for preventing operation of said first valve means to reverse the flow of pressure fluid to said motors for a predetermined interval subsequent to operation thereof to disconnect said fluid pressure sources from said motors, fourth valve means for selectively connecting said supplemental fluid pressure source to the first member ends of one or the other of said motors, and means placing said fourth valve means during said interval and when said first member is not being operated up or down under the control of said first means connected to said bridge means for controlling actuation of said fourth valve means whereby said supplemental fluid pressure source is connected to the first member end of the leading motor of said motors during said interval and While said first member is not being operated during a 21 predetermined unbalance in said bridge means in excess of said lrst predetermined unbalance.

5. In a control system for a device of the character described having a supporting means or frame, a member, a plurality of pressure lluid operated motors connected to said supporting means and to said member at spaced points for producing movement of said member relative to said supporting means, a rst fluid pressure source, valve means for selectively connecting said first uid pressure source to the frame end of said motors or to said member ends of said motors, means for preventing operation of said valve means to prevent the ow of uid to said motors, a second fluid pressure source, second valve means for connecting said second fluid pressure source to the frame end of said motors or to said member ends of said motors, means for sensing variations of said member from a predetermined attitude relative to said supporting means, means actuated by said sensing means to actuate said second valve means to connect the frame end of said motors to the second pressure fluid source, and means actuated by said sensing means to actuate said second valve means to connect said second pressure fluid source to the said member ends of said motors when the means for preventing operation of said lirst valve means is effective.

References Cited in the ile of this patent UNITED STATES PATENTS 2,309,944 Flowers Feb. 2, 1943 2,353,388 Cannon July 11, 1944 2,484,908 Purcell Oct. 18, 1949 2,565,639 Waldie Aug. 28, 1951 2,906,096 Richardson Sept. 29, 1959 2,915,961 Parkinson Dec. 8, 1959 Patent No. 3,031,950 May l, 1962 Ralph P. Anderson et al.

.stifled that error appears in the ion and that the said Letters Paten s It is here f ent requiring co corrected below.

line 33, strike out "first" and insert the Column 19 for "second same after "said", first occurrence; line 34, movable" read movable second Signed and sealed this 11th day of September 1962.

(SEAL) Attest: `ERNEST w. swIDER DAVID L. LADD Commissioner of Patents Attesting Officer

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