US2958199A - Hydraulic press - Google Patents

Description

Nov. 1, 1960 Filed March l2, 1959 R. P. ANDERSON ET AL HYDRAULIC PRESS 5 Sheets-Sheet 1 4free Eys Nov. 1, 1960 R. P. ANDERSON ETAL HYDRAULIC PRESS 5 Sheets-Sheet 2 Filed March 12, 1959 Nemi. l

llril INVENTORS kan# /l/voERsO/v Roy E Oe-HN BY I 7l I l l rrcRNEys R. P. ANDERSON Erm. 2,958,199

HYDRAULIC PRESS 5 Sheets-Sheet I5 Nov. 1, 1960 Filed March l2. 1959 JNVENTORS RALPH A Afvofeso/v By Aoy E 01E/w Q', @r/@wwf Afro/eA/ EYS Nov. l, 1960 RI P. ANDERSON ETAL 2,958,199

HYDRAULIC PRESS 5 Sheets-Sheet 4 Filed March l2, 1959 JNVENToRs PMP/f EAA/@Eason /Poy F 9er-IN WM I fl ArroR/EYS Nov. l, 1960 R. P. ANDERSQN ETAL HYDRAULIC PRESS Filed March 12, 1959 5 Asheets-sheet 5 rToR/VEXS 2,958,599 Patented Nov. 1, 1960 'tic HYDRAULIC SS Ralph P. Anderson, Willoughby, and Roy 1T.. Dehn, Wickliffe, Ohio, assignors to The Cleveland Crane 8; Engineering Company, Wickliife, Ohio, a corporation of Ohio Filed Mar. 12, 1959, Ser. No. 798,964

8 Claims. (Cl. *6d- 97) The present invention relates to devices having a mov able member actuated by a plurality of reciprocating type hydraulic motors and wherein it is necessary or desirable to have the movable member travel o-r move in a predetermined manner with respect to a stationary member or some predetermined reference plane.

One of ythe principal objects of the invention is the provision of a novel and improved device for bending or otherwise fabricating sheet material or the like, for eX- ample, a platen press, press brake, etc., having a movable member of substantial size in at :least one dimension actuated by a plurality o-f reciprocating type double acting hydraulic motors connected to the movable member at relatively widely spaced points which machine will be relatively light in weight, simple in design and rigid in construction, reliable in operation and which comprises means for supplying pressure fluid to the respective motors in such a manner that .the movable member moves, preferably in both directions, in a relatively exact or precise predetermined attitude or manner, for eX- ample, parallel with or inclined `at a predetermined angle to the stationary platen, blade, etc.

A more specic object of the invention is the provision of a novel and improved metal working press device having an elongated movable member actuated by fa pair of reciprocating type double acting lluid pressure operated motors connected to the movable member adjacent to opposite ends thereof in combination with means for supplying pressure fluid to the motors and including an electric bridge responsive to deviation of Ithe movable member from a predetermined attitude relative to a stationary part of the devices for controlling the relative flow of pressure fluid to the motors whereby the movable member is automatically restored to the predetermined attitude or a predetermined attitude is maintained.

Another of the principal objects of the invention is the provision of a novel and improved means for controlling the supply or ow of Huid pressure to a plurality of reciprocating type hydraulic motors preferably of the double acting type such that the motors are operated in precise predetermined relation to one another.

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 illustrative embodiment of the invention described with reference to the accompanying drawings forming a part of this Yspecification in which similar reference characters `designate corresponding parts and in which Fig. 1 is a front elevational View of a sheet metal or plate bending brake or press embodying fthe present invention;

Fig. 2 is a diagrammatic View showing the hydraulic system and the mechanical part of the leveling control; and

Figs. 3, 4 and 5 .together form a wiring diagram showing the electrical control for the press.

The present invention is considered especially applicable to bending presses or brakes and is herein shown as embodied in s-uch a press. It is, however, to be understood that the invention is applicable to various types of presses and other machines utilizing multiple pressure uid 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 reference character A designates a frame comprising stress-resisting, plate-like end members or side housings 10, 11 having aligned openings in their front edges; a combination reservoir and sump interposed between and supported by the upper ends of the side housings lil, 11; and a table or die support 113 supported and iixedly secured to the top of a heavy plate or stationary blade 14 extending between and iXedly secured to the side housings 10, 11.

A movable ram or upper blade, designated generally by the reference character B, located directly above the table or die support 13 is slidably supported by the side housings for linear movement towards and from the table or die support. The lower edge of the ram B is adapted to carry a suitable punch or other tool.

The ram or movable blade B is adapted to be reciprocated ,towards and from the table or die support 13 by reciprocating type double acting uid pressure motors designated generally by reference characters C, D. The cylinders 20, 2l of the motors C and D, respectively, are connected to the side housing 10, 11 respectively, of the press frame and the piston rods 22, 23 of the motors are connected by ball and socket connections or joints 24, 25 to the 'blade B adjacent to opposite ends thereof. The principal pressure liuid, preferably oil, for operating the hydraulic motors C, D is supplied by two constant volume unidirectional main pumps E, F driven by an electric motor 26. The pumps E, F supply pressure uid to the hydraulic motors C, D respectively. An auxiliary or third constant volume unidirectional pump G driven by an electric motor 27, in conjunction with an electronic control, supplies pressure fluid to the hydraulic motors C, D for maintaining a predetermined blade or ram attitude. The pumps and motors as well as a number of the other parts of the hydraulic system hereinafter referred to are supported upon the top of the reservoir l2 which is in the form of an elongated rectangular oil tank or sump S extending between `and connected to op* posite end housings 1t), 11.

Referring to the schematic hydraulic and electrical wiring diagrams, Figs. 2, 3, 4 and 5, and assuming that the reciprocable blade B is in its raised position, the motors 26, 27 are started by depressing the start push button switch 35. The depressing of the start push button switch 35 establishes a circuit from an input power line 36 through the normally closed stop push button switch 37, wire 38, now closed start push button switch 35, wire 40, operating solenoid 4l of relay 42, wire 43, normally closed motor overload contacts 44, associated with the controller for the motor 26, wire 45, and nor-` mally closed motor overload contacts 47 associated with the controller for the motor 27 to power line 48. The energization of the operating solenoid 41 of relay 42 closes a pair of normally open contacts 50 which establish a holding circuit for the relay 42 about the start push button switch 45, which may now be released. The energization of the operating solenoid 41 of the relay 42 also closes normally open contacts not shown which energizes the operating solenoid of the motor starters not shown for the motors 26 and 27. The relay 42 further includes normally open contacts 51, '52 which are closed upon the energization of the its operating coil 41 to connect a control circuit, hereinafter described, to the power lines 36, 48.

The control circuit mentioned includes a three-position selector switch, designated generally by the reference character 55, by which different cycles of operation of the pressbrake can be selected. When the selector switch 55 is in one position, hereinafter referred to as the single stroke or iirst position, the press will operate to execute a single stroke non-repeat cycle upon the depressing of the start pedal switch 56 regardless of Whether or not the operator keeps his foot on the switch or releases it immediately after the down stroke has begun. When the selector switch 55 is in the second position, the ram will move down as long as the operator maintains his foot on the pedal switch 56, and will move up when the operator releases the switch. When the selector switchfSS is moved to the third position, the ram B can be inched down by the manually operable push button switch 57 or by use of the pedal switch 56, or the ram can be inched up by the manually operable switch 58. The switches 57, 58, as well as the start and stop switches 35, 37 may be located at any convenient place about the machine.

When the ram is inoperative with the motors 26 and 27 running, the main pumps E, F discharge to the sump S through pressure controlled relief valves 65, 66 connected between their discharge conduits 67, 68, respectively, and the sump. The control cylinders of the relief valves 65, 66 are connected to a conduit 68 by suitable conduits 70, 71 having suitable check valves 72, 73 therein, respectively. The conduit 68 is adapted to 'ne selectively connected to the sump S through a twoposition solenoid operated venting valve 75, normally spring biased to its open position. When the valve 75 is closed, the maximum pressure of the hydraulic fluid in the conduit 68 and in turn the relief valves 65, 66 is controlled by a remote tonnage control adjustable relief valve 76. This valve can be adjusted so as 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 10, 11. The reference character 77 designates a pressure gauge connected to the conduit 68. This gauge is preferably located adjacent to the adjustment for the tonnage control relief valve and is preferably graduated in tons of pressure exerted by the ram B. The tonnage control relief valve 76 determines the pressures at which the relief valves 65, 66 open to vent the pumps E, F when the vent valve 75 is closed.

The auxiliary or leveling pump G is connected to a conduit 80 connected to the sump by an adjustable relief valve 81 similar to the relief valves 65, 66 and having its control chamber or cylinder connected to the conduit 68 by a conduit 82 provided with a check valve 83. A check valve 84 inserted in the conduit 68 between the connections therewith of the conduits 70, 82 prevents the ow of uid from the conduit 82 through the venting valve 75 when the venting valve is open. The pressure setting for the relief valve 81 connected to auxiliary pump G is always determined by and under the control of the maximum tonnage valve 76.

With the selector switch 55 in its iirst position; that is, the single stroke position, the'press will go through one down and up cycle and stop at the top of the stroke when the operator presses pedal switch 56 momentarily, to open its normally closed contacts 85, 86 and close its normally open contacts 87, 88. This will occur whether the operator keeps his foot on the pedal switch 56 or not. The closing of the normally open contacts 87, 88 of the pedal switch 56 establishes a circuit from the power line 36 through the now closed contacts I51 of relay 42, wire 90, normally closed contacts 91, 92 of maximum out of level switch 93, wire 94, normally closed contacts 95 of relay 96,V Wire 97,V now closed contacts 87, 88, Vwire 98, normally closed contacts 100 of non-repeat or latchV relay 101, wire 102, normallyV closed contacts 103, 104 of down limit switch 105, wire 106, normallyclosed con- CTL 4 tacts 107 of relay 108, wire 110, operating solenoid 111 of down relay 112 to wire 113, and now closed contacts 52 of relay 42 to line 48. The encrgization of the operating solenoid 111 of relay 112 closes its normally open contacts 115, 116, 117, 118, 119, 120, 121, 122, 123 and opens its normally closed contacts 124. The closing of contacts establishes a holding circuit for relay 112 around the start pedal switch 56 from the wire 97 through the now closed contacts 125, 126 of selector switch 55, wire 127, and now closed contacts 115 to wire 102, which maintains the relay energized even though the operator may remove his foot from the pedal switch 56. The closing of the normally open contacts 116 of relay 112 establishes a circuit from the wire 90 through the now closed contacts y116, Wire 130, now closed contact 131, 132`of selector switch 55, wire 133, and latching coil 134 of single stroke or latch relay 101 to wire 113. Energization of the operating solenoid 134 of relay 101 opens its normally closed contacts 100 in series circuit with contacts 87, 88 of switch 56 and closes its normally open contacts 135. The opening of the normally closed contacts 100 breaks the circuit through the contacts 87, 88 of start switch 56 even though the press closes and opens with theV operator maintaining his foot on the pedal switch 56 then holding the contacts 87, 88 closed. Closing normally open contacts 135 of relay 181 does not unlatch relay 101 this time because in the interim, the ram B has moved away from its top position opening the up closed contacts 136, 137 of up limit switch 138. Almost concurrently with the opening of the up closed contacts 136, 137 of the up limit switch 138, the up- open contacts 140, 141 of the limit switch close. This, however, does not perform an operation since the normally closed contacts 124 of down relay 112 are now open.

The closing of the normally open contacts 117, 118 of relay 112 establishes a circuit from the line 36 through the now closed contacts 117, wire 142, solenoid 143 of decompression Valve 144, wire 145, now closed contacts 118 of relay 112 to line 48. The energization of solenoid 143 of the decompression valve 144 operates the decompression valve to close the same.

The closing of normally open contacts `119, of relay 112 establishes a circuit from the line 36 through the now closed contacts 119 of relay 112, Wire 146, operating solenoid 147 of a solenoid operated three position fourway, directional pilot valve `1.48, normally biased to its center position, Wire 149, and now closed contacts 120 of relay 112 to line 48. Energization of the solenoid 147 of pilot valve 148 shifts the valve spool to the right as viewed in Fig. 2 and connects the pressure conduit 67 leading from the pump E to a conduit 150 leading to a hydraulically operated three posit-ion four-way directional valve 151 normally biased to its central position, causing the valve 151 to be shifted to the left to connect a conduit 152 to a conduit 153- leading to the head end of cylinder 20 of motor C. The conduit 152 is connected to the conduit 67 by a check valve 154.

The closing of normally open contacts 121, 122 of relay 112 establishes a circuit from the line 36 through the now closed contacts 121 of relay 112, wire 160, operating solenoid 161 of a solenoid operated three position four-way directional pilot Valve 162 normally biased to its center position, wire 163 and now closed contacts 122 of relay 112 to line 48. Energization of solenoid 161 of pilot valve 162 shifts the valve to the right and connects the pressure conduit 68 leading from the pump F to a conduit 163` leading to a hydraulically operated three position four Way directional valve 164 normally biased to its center position, causing the valve 164 to shift to the left and connect a conduit 1653 to a conduit 166 leading to the head end of cylinder 21 of motor D. The conduit 165 is connected to the conduit 67 leading from the pump F by a check valve 167.

The closing of the normally open contacts `123 of relay `112 establishes a circuit from the line'90 through the now closed contacts 1323,01? relay 112, wire 170, normally closed contacts 171, 172 of down limit switch 105, wire 173, normally closed contacts 174 of relay 175, wire 176, normally closed contacts 177 of relay 178, wire 180, and operating solenoid 181 of relay 182 to wire 1131. EnergiZa-tion of the .operating solenoid 181 of relay 182 closes Vits normally open contacts 183, 184 establishing a circuit from the line 36 through the now closed contacts 183, wire 185, operating solenoid 186 of venting valve 75, wire 187, and now closed contacts 184 to line 48. Energization of the operating solenoid 186 of venting valve 75 closes this valve thereby stopping the venting of the pumps E, F, causing them to build up pressure.

'Ilie main pumps E, F will now pump oil through conduits 67, 68, check valves 154, 167, conduits 152, 165, directional va-lves 151, 164, and conduits 153-, 166 to the head ends of the cylinders 20, 21 of the motors C, D, respectively. As the ram moves away from its uppermost position, a sp-ring bias in limit switch 138 will immediately open contacts 136, 137 o-f the switch and close contacts 140, 141 thereof as previously stated.

As the ram B moves down, and assuming that the rapid advance rfeature hereinafter referred to is not being used, the fluid in the bottom of the cylinder of motor C ilo-ws to the sump S through conduit 199, counterbalance valve 20.0 and conduit 201 to a two-way hydraulically operated rapid advance valve 202 which yis normally in the position shown in Fig. 2. After flowing through the rapid advance valve 202 the fluid ows through a conduit 203` to directional valve 164, which is now shifted to the left connecting the conduit 203 to a conduit 204 leading to the sump S. In like manner the iluid in the bottom of cylinder 21 of motor D ows to the sump S by way ,of conduit 205, the counterbalance valve 206, conduit 207, rapid advance valve 208, conduit 209, directional valve 151, and conduit 210 to sump S. The counterbalancing valves 200, 2061 are adjustable and open upon the attaining of the desired pressure in the lower ends of the cylinders 20, 21. These Valves are normally set so as to maintain the ram B in its topl position, that is, at the end of its up stroke when the press is not operating.

The ram B will move down until a cam on the ram actuates down limit switch 105 to open its normally closed contacts 103, 104 and 171, 172. The opening of contacts 103, 104 breaks the holding circuit for relay 1.12 through contacts 115 causing its now closed but normally open contacts 115 to 123 to open, and its now open but normally closed contacts 124 to close. The opening of contacts 117, 118 deenerm'zes thedecompression valve 144 reconnecting conduits 153, 166 to sump S` through check valves 220, 221 `and needle valves 222, 223 located in the respective conduits. The opening of contacts 123` of relay 112 deenergizes the operating solenoid 186 of venting valve 75 allowing the Valve to open and connect the conduit 86 to the sump and in turn the pumps E, F to sump S through the now vented relief valves 65, 66.

The opening of contacts 119, 120 and 121, 122 of relay 112 deenergizes the down solenoids 147, 161 of directional pilot valves 148, 162 causing the directional valves 151, 164 to return to their normal position.

The reclosing of the normally closed contacts 124 of relay 1.12 now establishes a circuit from the line 36 through now closed contacts 511 of relay 42, wire 90, closed contacts 91, 92 of maximum out of level switch 93, wire 94, now closed contacts 95, of relay 96, wire 97, now closed contacts 225, 226 of selector switch 55, wire 227, normally closed contacts 228 of relay 96, wire 230, now closed contacts 140, 141 of up limit switch 138, wire 231, now closed contacts 124 of relay 112, wire 232, operating solenoid 233` of time delayed closing relay 234, wire 113 and now closed contacts 52 of relay 42 to line 48. After a predetermined interval sucient to permit decompression of the oil in `the cylinders, con- 6 duits, etc., previously under pressure normally open contacts 240 of time delayed closing relay 234 close establishing a circuit from the wire 232 through the wire 241 and operating solenoid 242 of up relay 108.

Contacts 251, 252 of relay 108 are in parallel circuit with contacts 117, 118 of down relay 112 and in series circuit between the lines 36, 48 with the operating solenoid 143 of decompression valve 144 from which it follows that the closing of contacts 251, 252 closes Ithe decompression valve 144. Contacts 253, 254, 255, 256 of relay 108 are in series circuit with the up solenoids 260, 261 of the direction pilot valves 148, 162, respectively, between the lines 36, 48 and the closing of these contacts energizes the solenoids 260, 261, to shift the pilot valves 148, 162 to the left and connect the pressure conduits 72, 73 to the conduits 263, 264 leading to the left hand sides of the directional valves 151, 164 as viewed in Fig. 3. This shifts the directional valves 151, 164 to the right connecting the left hand pump E to the lower end of the cylinder 21 of right hand fluid pressure motor D and the right hand pump F to the lower end of the cylinder 20 of the left hand tluid pressure motor C through the rapid advance valves 208, 202, respectively, which are now in their normal position shown in Fig. 2.

The energization of operating solenoid 242 of up relay 108 operates the relay to open its normally closed contacts 107 and close its normally open contacts 250, 251, 252, 253, 254, 255, 256. The opening of contacts 107 which are in series circuit with the operating solenoid 111 of down relay 112 prevents operation of this relay after the ram B has started its upward or return stroke and contacts 103, 104- of down limit switch 105 have closed, even though the operator retains the pedal switch 56 depressed or depresses it again before the ram B has returned to its up or starting position.

The closing of contacts 250 of relay 108 establishes a circuit lfrom the wire through the now closed contacts 250, wire 173, normally closed contacts 174 of relay 175, wire 176, normally closed contacts 177 of relay 178, wire 180, and operating solenoid 181 of relay 182 to wire 113, causing the relay to operate to close its normally open contacts 183, 184, energizing the operating solenoid 186 of venting valve 75, causing the pumps E, F to build up pressure in the conduits 67, 68 respectively.

From the pump E oil flows through conduit 72, check valve 154, .conduit 152, directional valve 151, conduit 209, rapid advance valve 208, conduit 207, check valve 265 which by-passes counterbalancing valve 206, and conduit 205 to the lower end of cylinder 21 of motor D. From the pump F oil flows through conduit 73, check valve 167, conduit 165, directional valve 164, conduit 203, rapid advance valve 202, conduit 201, check valve 266 which by-passes counterbalance valve 200, and conduit 199 to the bottom of cylinder 20 of motor C.

The ram B continues to raise until a trip thereon actuates the up limit switch to reopen its contacts 140, 141 thereby deenergizing the operating solenoid 242 of up relay 108 allowing its normally open contacts 250-256 to open thereby opening vent valve 75 and decompression valve 144, and permitting directional valves 151, 164 to return to their normal positions and causing the ram B to stop in its up position.

As the ram B approaches the top of its stroke contacts 140, 141 open and the ram stops as described. Contacts 136, 137 of up limit switch reclose and, when and if the pedal switch 56 is released, establishes a circuit through the normally closed contacts 85, 86 of start switch 56, wire 270, now closed contacts 136, 137, wire 271, now closed but normally open contacts of single stroke latching relay 101, wire 272, and unlatchingsolenoid 273 of relay 101 to wire 113 resetting the relay fora subsequent cycle of operation.

The cycle of operation just ldescribed can be repeated by the operator again depressing the start pedal switch 56.

With the selector switch 55 set in its second position the previously closed contacts 125, 126 are open thereby preventing the establishment of a holding circuit for down relay 112 with the result that the ram stops when the pedal switch 56 is released. The wire 227 which is in series circuit with the operating solenoid 242 of up relay 108 is now connected to Wire 270 Vsince contact 226 is now connected to contact 274 and when the start pedal switch is released to close its normally closed contacts 85, 86 the operating solenoid 233 of time delay relay 234 is energized and in turn the operating solenoid 242 of up relay 108 is energized to cause the press to move up until the ram B reaches the end of its upward movement and opens contacts 140, 141 of up limit switch 138 or until the operator again depresses pedal switch 56.

When selector switch 55 is set in its third position to close contacts 125, 280 and contacts 226, 281 the blade may be jogged down by depressing the pedal switch 56 or the manually operable push button switch 57. This establishes a circuit from the wire 97 through now closed contacts 125, 280 of selector switch 55, wire 282, now closed contacts 283, 284 of switch 57 to wire 102 and in turn to operating solenoid 111 of down relay 112 and wire 113. The circuit will be maintained as long as the switch 57 is held depressed by the operator. The depressing of the up inch or jog push button switch 58 to close its normally open contacts 285, 286 establishes a circuit from the wire 97 through the now closed contacts 125, 280 of selector switch 55, wire 280, now closed contacts 285, 286 of jog up push button switch 58, wire 287, and now closed contacts 281, 226 of selector switch 55 to wire 227 and in turn through Ioperating solenoid 233 of time delayed opening switch 234 to wire 113 the closing of the normally open contacts 240 of which energizes the operating solenoid 242 of up relay 108.

The rapid advance valves 202, 208 are provided to provide a quick or rapid approach of the ram to working position. When these valves are actuated in a manner lhereinafter referred to, oil from the lower ends of cylinders 20, 21 of hydraulic motors C, D is diverted to the upper ends of the opposite cylinder instead of being returned to the sump. This increases the rate of movement of the ram. The actuation of the rapid advance valves is under the control of a rapid advance switch 288 adapted to be actuated by an elongated cam 290 on the movable ram VB throughout a predetermined part of the down stroke of the ram. The rapid advance feature, however, can only be operative during the down stroke of the press and then only when the selector switch 55 is in its lirst position, that is, in the position in which the press goes through one complete cycle of operation upon instantaneous depression of the pedal switch 56 by the operator.

The closing of the normally open contacts 291, 292 of rapid advance switch 288 establishes a circuit from the Wire 90 through closed contacts 116 of the down relay 112, wire 130, now closed contacts 291, 292 of rapid advance switch 288, wire 294, normally closed contacts 295 of relay 175, wire 296, normally closed contacts 297 of relay 178, wire 300 and yoperating solenoid 301 of rapid advance relay 302 to wire 113. This actuated rapid advance relay 302 to close its normally open contacts 304, 305 and 306, 307, the rst two of which are in series circuit across the lines 36, 48 with the operating solenoid 310 of the solenoid operated two position rapid advance pilot valve 311 and the latter two of which are in series circuit across the lines 36, 48 with the operating solenoid 312 of the solenoid operated two position rapid advance pilot valve 313.

The rapid advance pilot valves l311, 313 are springbiased to the position shown in Fig. Zand the solenoid operated to their other position. VEnergization Vof the operating solenoids 310, 312 of the rapid advance pilot valve connects the pressure supply lines 67, 68 with conduits 314, 315, leading tothe left-hand ends Vof the main valves 202, 208 respectively, causing the main 8 rapid advance valves to shift to their right-hand positions thereby connecting the return conduits 201, 207 to the fluid pressure supply conduits 166, 153 leading to the upper ends of the cylinders 21, 20 of the motors D, C, respectively. When the switch 288 opens upon the ram B reaching a predetermined point in its downward movement the circuit is brokenfor the'solenoid 310, 312 of the rapid advance pilot valves permitting the pressure supply conduits 67, 68 to be connected to conduits 316, 317, respectively, leading to the righthand ends of the main rapid advance valves 202, 208 respectively, causing the valves to be returned to their normal positions, that is, Vthe positions shown in Fig. 2.

The rapid advance feature will inherently produce some tendency to correct unequal speeds of the motors due to they fact that the motors are cross connected, that is, if the piston of motor C is travelling down faster than the piston of motor D oil flowing from the lower end of cylinder 20 of motor C will iiow at a faster rate than the oil owing fromV the lower end of cylinder 21 of motor D and since the oil owing from the lower end of cylinder 20 yof motor C goes into the top end of cylinder 21 of motor D, the piston therein will be advanced more rapidly than the piston in motor C, thus tending to correct the unequal speed of the motors.

It will be apparent that as a press operation is performed, one end of the ram or blade B may lead the other because the Vpump C, D may not pump exact amounts of oil and/or the load or resistance to movement of the ram or blade B may not be uniformly distributed 'between the two pumps. In most instances, it is desirable to have the movable bladeV B and the punch or punches carried thereby remain at aconstant angle with respect to the fixed blade and die or dies throughout the operation and the present press incorporates means for controlling the oW of pressure uid to the respective motors C, D in such a manner that they move at a uniform speed regardless of the resistance encountered, etc. Y

This mechanism is herein referred to as the blade attitude or leveling control and includes a blade at. titude sensing mechanism comprising an electric bridge designated generally as H and located in the housing 330 which bridge produces a signal when the blade is out of atitude or level and amplifying circuits for determining the polarity and magnitude of the signal and changing and/or stopping the ow of pressure fluid to the respective motors C, D in accordance to the signal, to restore the ram B to its predetermined angular position relative to the die table 12.

The attitudeV sensing mechanism shown comprises an H-shaped armature 331 made of magnetic material and having an electric coil surrounding each of the respective arms of the armature. The coils are designated 332, 333, 334, 335 and are connected to the alternating current power supply lines 36, 48 in such-a manner that they form an impedancebridge similar to a Wheatstone bridge. The coils 332-335 are xed to the frame of the press, in the present instance to the right-hand side housing 11, and the armature 321 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 331 is biased towards the rear of the press by a tension spring 336 connected thereto and to a pin 337 connected to the side housing 11 of the press and is adapted to be moved towards the front of the press by a relativelyV nonelastic, exible steel band 340 connected theretoand extending in a forwardly directionY from the armature, that is, in a direction opposite to the spring V336. From the armature 331the flexible steel band 340 passes about a sheave or pulley 341 fixed to the frame member 11 and then abouta sheave342 fixed to the rear side of the right hand end `of the movable ram B. VFromv `the sheave 342 the exiblerband extends generally horizontally across the rear of the ram B and passes over a sheave 343 connected to the left-hand end of the ram B which extends to the outside of the left-hand side plate 10. From the sheave 343 the ilexible steel band extends downwardly in a generally vertical direction and has its end secured to the upper end of a member 344 adjustably connected to a member 345 which member is in turn connected to the side housing 10. The member 344 projects through the member 345 and the lower end thereof is threaded and provided with a narrow nut 346 which facilitates adjustment of the member 3144 relative to the member 345 and in turn the position of the H frame 331 in the bridge solenoids 332-5. By adjustment of the member 344, the armature 331 can 4be adjusted relative to the coils 332-335 to balance the bridge circuit, 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 B with reference to the die table 12 will cause the armature 331 to move away from its neutral position and a signal to appear across its output or control terminals 347, 348. The magnitude and polarity of the signal will be a function of the blade attitude or out of balance. This signal is applied to two amplifying circuits each comprising a pair of thyratron tubes 350, 351 and 352, 353, respectively. The first circuit responds to a small out of balance condition to cause additional oil to be pumped by the auxiliary or balancing pump G to the trailing hydraulic motor. if the out of balance condition exceeds that which can be taken care of by the auxiliary pump G the second circuit causes the venting valve 75 to open and the main pumps to be temporarily rendered ineffective to supply oil to the hydraulic motors C, D.

A complete circuit is shown in the wiring diagram but will not be herein .described in detail. Suilice it to say that as the armature 331 moves in opposite directions from its neutral position the voltages across the bridge terminals 347-348 will be 180 out of phase with one another. The change of phase indicates or senses which end of the ram is lagging and the magnitude of the output voltage of the bridge circuit indicates or senses` the amount that the rarn 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 38-48, which supply alternating current. The Voltage impressed upon the plate circuits of the thyratron tubes 351), 351 and 352, 353 cornes from opposite sides of a mid-tapped secondary 354 of a transformer 355. The voltage impressed upon the plates of tubes 350 and 352 will be 180 out of phase with the voltage impressed upon the tubes 351 and 353. When an output voltage appears across the terminals 347, 348 of the bridge circuit, this voltage will be essentially in phase with the plate voltage with one of the tubes of each set 350, 351 and 352, 353 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 356, 357 in the output of a full wave rectifier indicated generally by the reference character K which supplies the negative bias to the tubes 358-353. The rheostat 356 is in the rst stage circuit including the tubes 350, 351 and con- -trols the first stage circuit, .and the rheostat 357 is in the second stage circuit which includes the tubes 352, 353. A transformer 358 is used to isolate the signals. The rheostats 356, 357 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. rI`his means that the greater the negative bias the further the ram B 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 rst stage so that the operation of the first and second circuits is progressive as the out-of-balance condition of the ram B increases. The grid circuits ofthe latter are connected to the bridge terminals.

The plate circuits of the tubes 350, 351 are connected t0 operating solenoids 360, 361 of relays 362, 363 having normally open contacts 364, 365 and 366, 367 in series circuit with operating solenoids 368, 369 of solenoid operated three position, four way balancing or at titude valve 378 is selectively operable to connect the pressure fluid supply line from the balancing pump G to the respective conduits 152, leading from the main pumps E, F to the directional valves 151, 164 respectively. Normally open contacts 375, 376 of a relay 377 are in series circuit between the lines 36, 48 with the normally open contacts 364, 365 of relay 362 and solenoid 368 of attitude valve 370. Similar contacts 380, 381 of relay 377 `are in series circuit between the lines 36, 48 with the normally open contact 366, 367 of relay 363 and solenoid 368 of attitude valve 370. The operating solenoid 382 of relay 377, however, is energized and the contacts 375, 376 and 380, 381 thereof are closed during the normal operation of the press since one side of the operating solenoid 382y is connected to the wire 97 by the normally closed contacts 383 of reset ram level relay 96 and wire 384 and the other side directly to wire 113.

Assuming that the ram B is moving down, that the hydraulic motor C is lagging and that the signal on the grid tube 358 is in phase with the plate voltage of the tube and of sutiicient amplitude to fire the tube, relay 362 is operated to close its normally open contacts 364, 365 and energize operating solenoid 368 of valve 370 thereby shifting the valve to the right as viewed in Fig. 2 to connect the pressure uid conduit 80 leading from the balancing pump G to conduit 152 which is now supplying pressure iluid tothe left-hand motor C. The signal regains control of the tube 350 after each half cycle and as long as a positive signal in excess of the predetermined amount remains on the grid circuit of tube 350i, the ow of pressure fluid to motor C from the main pump E will be supplemented by pressure fluid from the balancing or auxiliary pump G. As soond as the left-hand end of the ram B catches up with the right-hand end the positive bias disappears from the grid of tube 350, relay 362 opens and balancing valve 370 returns to its central position disconnecting the pump G from conduit 152. If the hydraulic motor D should lag the motor C, a signal in phase with the plate voltage of tube 351 will appear on the grid of tube 351 energizing relay 363 and in turn operating solenoid 367 of balancing valve 370 causing the .auxiliary pump G to pump oil into the conduit 165 suph plying oil from the main pump F to the motor D in a manner similar to that described with respect to motor C. If the out of balance condition cannot be corrected by the balancing pump G and increases to an amount suicient to raise the in phase signal on the grid of one of the tubes 352, 353, depending upon whether the lefthand motor C or the right-hand motor D is lagging the other lrespectively the tube ires or conducts energizing the selected one of relays 175, 178 to open its normally closed contacts 147, 295 and 177, 297, respectively. The contacts 147, 177 are in series circuit with the operating solenoid 181 of venting relay 182 and the contacts 295, 297 are in series circuit with the operating solenoid 301 of rapid advance relay 302 thus allowing the rapid advance valves 282, 208 to return to their normal spring biased position if they are in their other positions at the time, and allowing the venting valve 75 to open thereby venting the relief valves 65, 66 and discontinuing the flow of oil from the main pumps E, F to the motors C, D

1l but continuing the flow of oil from the auxiliary pump G to the lagging motor.

lf either end of the ram B leads the other at any time a predetermined amount in excess of the amount required to tire the second stage tubes 352, 353, the maximum out of balance switch 93 will be operatedvby a cam on the armature 331 to open its normally closed contacts 91, 92 and stop the press and close its normally open contacts 400, y401. The level of theram B can then be manually reset by the operator `depressing the reset push button switch 402 to close its normally open contacts 403, 404. This establishes a circuit from the wire 90 through the now closed contacts '400, 401 of maximum out of balance or safety switch 93, wire 405, now closed contacts 403, 404 of reset push button switch 402, wire 406 and operating solenoid 407 of relay 9d to wire 113. Energization of operating solenoid 407 of relay 96 opens its normally closed contacts 9S, 228, 383 and closes its lnormally open contacts 410, 411 energizing the time delayed closing relay 234 and in tum the up relay '108 to close the decompression valve 144 and set the directional valves 151, 164 in position to move the blade up and energize the reset relay 96 to set the out of balance valve 270 in the position in which the auxiliary pump G pumps oil into the lower end of the hydraulic motor connected to the lowest end of the ram B. As the ram returns to the level position contacts 91, 92 of maximum out of balance switch 93 reclose and the contacts 400, 401 of the switch reopen. This breaks the circuit for relay 96 and the ram stops or continues in an upward direction if the selecting switch 155 is in its rst or second positions until it reaches the top of its stroke.

From the foregoing it will be apparent that the objects heretofore enumerated and other have been accomplished and that a novel and improved device has been provided comprising a reciprocable member actuated by a plurality of pressure fluid operated motors connected thereto at relatively widely spaced points and extremely sensitive means including an electric bridge responsive to variations of the reoiprocable member from a predetermined attitude relative to a stationary or reference part of the device for temporarily supplementing the normal supply of fluid .to the lagging motor regardless of the direction of movement of the reciprocable member, and in the event the out of attitude condition exceeds a second predetermined attitude the means responsive thereto discontinuing the flow of fluid Ito lthe leading motor until the second predetermined attitude is restored.

While the preferred embodiment and alternative constructions have been described and referred to in considerable detail and while the electric bridge shown is of the reactor type, the invention is not limited to the constructions or to the type yof electric bridge shown and it is the intention to hereby cover all adaptations, modifications and uses thereof which come within the practice of those skilled in the art and the scope of the appended claims. The term impedance as used in this specification including the appended claims comprehends and includes either resistors and/or reactors.

Having thus described our invention, We claim:

1. In a ydevice of the character described a supporting frame, an elongated movable member, a plurality of pressure fluid operated reciprocating type motors connected to said frame and to said movable member at spaced points, a source of flu-id pressure, first electric solenoid operated valve means for selectively connecting and disconnecting said source of pressure iiuid to and from opposite ends of said motors, a first electric circuit forY control-ling the energization and de-energization of said first solenoid operated valve means, a second sourcerof liuid pressure, second electric solenoid operated valve means for selectively connecting and disconnecting said second source of pressure fluid to and from opposite ends of said motors, a second electric circuit for controlling the energization and deeenergization of said second ,solenoid operated valve means, one of said irst and second electricV circuits including an electric bridge means including two parallel circuits each comprising a plurality of electric impedance means, movable control means forming a part of said bridge means for varying the impedance of one`of said'impedance means, and means operatively connectedto said frame and to said movable member for varyingV the relative position of said movable control `means in said electric bridge means in response to variationsof said movable member from a predetermined attitude relative to said frame whereby the flow of pressure iiuid to said motors is controlled to maintain said predetermined attitude of said movable member.

2. Ina device of the character described a supporting frame-,fan elongated movable member, a plurality of pressure fluid operated reciprocating type motors connected to said frame and tol said movable member at spaced points, a source of iluid pressure, rst electric solenoid operated'valve mieans for selectively connecting and disconnecting said source of pressure fluid to and from opposite ends of said motors, a tirst electric circuit for controlling the energization and de-energization of said `lirst solenoid operated valve means, a second source of fluid pressure, second electric solenoid operated valve means for `selectively connecting and disconnecting said second source of pressure iluid to and from opposite ends of said motors, a second electric circuit for controlling the energization and de-energization of said second solenoid operated valve means, one of said iirst and second electric circuits including an impedance type electric bridge means, armature means forming a part of said bridge means, and means operatively connected to said frame and totsaid movable member for varying the relative position Vof said armature means in said electric bridge means in response to variationsrof said movable member from a predetermined attitude relative to said frame whereby the flow of pressure fluid to said motors is controlled to maintain said predetermined attitude of said movable member.

3. In a bending press of the character described a frame, an elongated movable ram, a plurality of pressure uid operated reciprocating type motors connected to said frame and to said ram at spaced points, a iirst source of fluid pressure, trst electric solenoid operated valve means for selectively connecting and disconnecting said source of pressure fluid to and from opposite ends of said motors, second solenoid operated valve means for selectively connecting the discharge ends of said motors to and from the inlet ends of said motors during at least a portion of their Working stroke for eifecting a rapid advance of said ram, a iirst electric circuit for controlling the energization and y'de-energization of said iirst and second solenoid operated valve means, a second source of iluid pressure, third electric solenoid operated valve means for selectively connecting and disconnecting said second source of pressure fluid to and from said motors, a second electric circuit for controlling the energization and de-energization of said third solenoid operated valve means, said second electric circuit including an impedance type electric bridge means, Varmature means forming a part of said bridge means, and-means operatively connected to said frame and to said ram for varying the relative position of said armature means in said electric bridge means in response to variations of said ram from a predetermined attitude relative to said frame whereby the flow of pressure uid to said motors is controlled to maintain said predetermined attitude of said ram.

4. In a press of the character described a frame, Van elongated movable member, a plurality of pressure iluid operated reciprocating type motors connected to said frame and to said movable member at spaced points, first and second sources of fluid pressure, first electric solenoid operated valve means for selectively connecting and disconnecting said iirst and second sources of pressure fluid to and from rst ends of Saidmotols and t0 and from opposite ends of said motors, a first electric circuit for controlling the energization and de-energization of said iirst solenoid operated valve means, a third source of iiuid pressure, second electric solenoid operated valve means for selectively connecting and disconnecting said third source of pressure fluid to and from said motors, a second electric circuit for controlling the energization and yde-energization of said second solenoid operated valve means, said second electric circuit including an impedance type electric bridge means, armature means forming a part of said bridge means, and means operatively connecte to said frame and to said movable member for varying the relative position of said armature means in said electric bridge means in response to variations of said movable member from a predetermined attitude relative to said frame whereby the iow of pressure fluid to said motors is controlled to maintain said predetermined attitude of said movable member.

5. In a device of the character described a frame, an elongated movable member, a plurality of pressure fluid operated double acting reciprocating type motors connected to said frame and to said movable member at spaced points, first and second sources of fluid pressure, first electric solenoid operated vailve means for selectively connecting and `disconnecting said rst and second sources of pressure liuid to and from first ends of said motors and to and from opposite ends of said moto-rs, a first electric circuit for controlling the energization and deenergization of said iirst solenoid operated valve means, a third source of iiuid pressure, second electric solenoid operated valve means for selectively connecting and disconnecting said third source of pressure fluid to and from the same ends of said motors to which said iirst and second sources are connected at any particular time, a second electric circuit for controlling the energization and de-energization of said second solenoid operated Valve means, said second electric circuit including an electr-ic bridge means including two parallel circuits each comprising a plurality of electric impedance means, movable means forming a part of said bridge means for varying the impedance of one of said impedance means, and means operatively connected to said frame and to said movable member for varying the relative position of said movable means in said electric bridge means in rei sponse to variations of said movable member from a predetermined attitude relative to said frame whereby the iiow of pressure uid to said motors is controlled to maintain said predetermined attitude of said movable member.

6. In a bending press of the character described a frame, an elongated movable ram, a plurality of pressure iiuid operated reciprocating type motors connected to said frame and to said ram at spaced points, tirst and `second sources of iiuid pressure, rst electric solenoid operated valve means for selectively connecting and disconnecting said source of pressure iiuid to and from irst ends of said motors and to and from opposite ends of said motors, second solenoid operated valve means for selectively connecting the discharge ends of said motors to and from the inlet ends of said motors during at least a portion of their working stroke for effecting a -rapid advance of said ram, a iirst electric circuit for controlling the energization and de-energization of said iirst and second solenoid operated valve means, a third source of iiuid pressure, third electric solenoid operated valve means for selectively connecting and disconnecting said third source of pressure iiuid to and from the same ends of said motors to which said rst and second sources are connected at any particular time, a second electric circuit for controlling the energization and de-energization of said third solenoid operated valve means, said second electric circuit including an impedance type electric bridge means, armature means forming a part of said bridge means, and means operatively connected to said frame and to said ram for varying the relative position of said armature means in said electric bridge means in response to variations of said ram from a predetermined attitude relative to said frame whereby the iiow of pressure iiuid to said motors is controlled to maintain said predetermined attitude of said ram.

7. In a bending press of the character described a supporting frame, an elongated movable ram, a plurality of pressure fluid operated reciprocating type motors connected to said frame and to said ram at spaced points, a first source of iiuid pressure, first electric solenoid operated valve means for selectively connecting and disconnesting said first source of pressure iiuid to and from opposite ends of said motors, a irst electric circuit for controlling the energization and de-energization of said iirst solenoid operated valve means, a second source of iiuid pressure, second electric solenoid operated valve means for selectively connecting and disconnecting said second source of pressure fluid to and from opposite ends of said motors, a second electric circuit for controlling the energization and de-energization of said second solenoid operated valve means, a third electric circuit for selectively controlling the energization and de-energization of said first solenoid operated valve means, an impedance type electric bridge means, movable means forming a part of said bridge means, means operatively connected to said frame and to said ram for varying the relative position of said movable means in said electric bridge means in response to variations of said ram from a predetermined attitude relative to said frame, means connecting said second circuit to said bridge means to energize said second circuit upon a predetermined signal existing across its output terminals to connect said second source of fluid pressure to the lagging motor of said motors, and means connecting said second circuit to said bridge means to energize said Ythird circuit upon a different signal existing across its output terminals to discontinue said iirst source of duid pressure.

8. In a device of the character described a supporting frame, an elongated movable member, a plurality of pres- Sure iiuid operated reciprocating type motors connected to said frame and to said movable member at spaced points, a first liuid pressure pump, a second iiuid pressure pump, a third liuid pressure pump, iirst electric solenoid operated valve means for selectively connecting and disconnecting said iirst and second pressure iiuid pumps to and from opposite ends of said motors, an electric circuit for controlling the energization and de-energization of said solenoid operated valve means, second electric solenoid operated valve means for selectively connecting and disconnecting said third pressure fluid pump to and from opposite ends of said motors, a second electric circuit for controlling the energization and de-energization of said second solenoid operated valve means, iiuid pressure controlled relief valves connected to the output circuits of said pumps, conduit means connected to said relief valves, means for supplying pressure fluid to said conduit means, and adjustable relief valve means in said conduit means.

Cannon July 11, 1944 Cannon July 11, 1944

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