US3507212A - Fluidic control circuit for presses - Google Patents

Description

April 21, 1970 D. J. MATTI-:SON

l FLUIDIC CONTROL CIRCUIT FOR PRESSES @01m n Nv 1A t X e e h s w 105.6 o NoNo m m/- l 3 moz@ u@ Nom N- om m@ Q z -IE Vl O NO N\/| o mOZm a om. 6 w m, om l .n o p A m n 292Go.. o F owzmw ATTORNEYS April 21, 1970 D. .1. MATTEsoN 3,507,212

FLUIDIC CONTROL CIRCUIT FOR PRESSES Filed April lO, 1968 3 Sheets-Sheet 2 Ful OTO- M ILM @mimi /e W uz l 5^@ PUSH To STOF( PULL To START BARBUN |V*.g OO\ 'Wrgig l I T M i l I L J 7e M FIG. 2

PRESS CRANKSHAFT POSITION (DEGREES) LSI o 9o |80 27o 36o DAV@ J M'Xlc FI G 3 LM 744m, ff: fw,

AT TOR N EYS April 21, 1970 D. .1Q MATTEsoN 3,507,212

FLUIDIG CONTROL CIRCUIT FOR PRESSES Filed April l0, 1968 5 Sheets-Sheet 5 SEAL-IN 428 AND GATE C, FlG. 4

LATCH-m cl AND GATE Cgoz $50 TOR-STOP b 46 0 66 -H-\ XCI 9 NOR /45 64/ C2 O2 l? START STGNAI. BRAKE CLUTCH INVENTOR.

DAVID J. MATTESON BY /l/feym, WMM @dy ATTORNEYS United States Patent O 3,507,212 FLUIDIC CONTROL CIRCUIT FOR PRESSES David J. Matteson, Drexel Hill, Pa., assignor to E. W. Bliss Company, Canton, Ohio Filed Apr. 10, 1968, Ser. No. 720,249 Int. Cl. B30b 15/10, 15/12, 15/16 U.S. Cl. 100-53 19 Claims ABSTRACT OF THE DISCLOSURE A fluidic control circuit especially suitable for control of presses wherein a fluid NOR gate provides a clutch signal in response to an input signal, and alternately, a 4brake signal with no input signal. The input to the NOR gate is provided by components which cause the press to run continuously, or on a single stroke basis, with means to bring the press to an emergency stop anywhere in the press stroke. Except for an emergency stop, provision is made so that the press stops only at the top of its stroke. An initial but momentary start signal activates the circuit and NOR gate clutch signal, the input to the NOR gate being maintained by an AND gate requiring continuous plural uid inputs so that should the uidic circuit be broken, or blocked in any way, the press will fail safe and stop.

The present invention relates to a uidic control circuit, and in particular, to such a circuit suitable for operation and control of a press.

It is known to provide an electrical circuit for presses and other types of machinery, comprising tubes, relays and other components arranged to cause the press or other type of machinery to carry out a number of functions.

Although the development of uidic components and circuits utilizing these components is only recent, experience to-date has shown that the fluidic components and circuits offer many advantages over comparable electrical components and circuits. For instance, it has been found that the uidic circuits are generally more reliable and dependable, and generally have a longer life not having components such as relays, subject to wear. When the circuits are preformed as an integrated assembly, they are tamper proof. In addition, it has been found that the fluidic circuits can be produced for less than the cost associated with comparable electrical circuits.

In proceeding from an electrical circuit to the design of a uidic circuit, the disadvantage arises that individual iiuidic components do not function or perform identically to the analogous electrical components. This requires, in the design of a fiuidic circuit, the use of different concepts and logic.

It is an object of the present invention to provide a uidic control circuit particularly suitable for the operation of a press.

It is a further object of the invention to provide a uidic control circuit for a press which is inexpensive comprising a minimum and optimum number of uidic components.

It is a further object of the present invention to provide a press control circuit which fails safe in the event of a break or disruption in the circuit.

In accordance with the invention, there is provided a fluidic press control circuit which alternately activates a clutch mechanism and a brake mechanism, deactivating at the same time the mechanism not activated, comprising a NOR gate including a clutch output connection and a brake output connection. A fluid input connection actuates the power fiuid ow in the NOR gate to the clutch output connection. An AND gate comprises an output connection in ow communication with the NOR gate input connection, -with means to interrupt either one or both of the inputs to the AND gate in the event any one of a number of stop conditions exists in the press. This in turn interrupts the NOR gate input shifting the output thereof t0 the brake output connection. At least one of the input connections to the AND gate receives a signal dependent upon completion of the press stroke so that with the eX- istence of a signal at the other input connection, the press if stopped is stopped only at the top of its stroke. This can be termed the normal stop input connection. An emergency stop means is provided in the AND gate circuit designed to interrupt the signal to the other input connection causing the press to be stopped immediately. The AND gate connection receiving this signal can be termed the emergency stop input connection.

Preferably, the normal stop input connection of the AND gate receives at least two signals both dependent upon position of the press crankshaft in its stroke, both existing for a period or periods of the press stroke. A rst means extends the first signal which can be termed a topstop signal for the period when the crankshaft is roughly between its point and its 270 point. A second means produces the second signal throughout the press stroke except it may be interrupted when the crankshaft is roughly at its point. This signal can be termed the repeat signal.

In the absence of a repeat signal, the AND gate output is shut 01T as the press passes the 270 point, the resultant absence of a NOR gate input bringing the press to a stop at approximately 360. A Preference Flip-Flop (PFF) gate provides the repeat signal from its non-preferred output connection. The input to the PPF gate which holds the output at its non-preferred or repeat signal output connection is received from a seal-in AND gate. This AND gate contains a memory circuit which remembers that the press was started, but in every cycle at the 180 position, a momentary input which can lbe called an anti-repeat signal is received at the 'PFF gate input connection opposite the input connection receiving the seal-in AND gate output, and in the absence of the latter, the PFF gate output or repeat signal is turned off. To terminate the sealin AND gate output, the AND gate is provided with a valve which interrupts the flow in its memory circuit.

The invention and advantages thereof will become apparent upon further consideration of the following specification, with reference to the accompanying drawings, in which:

FIGURE 1 is a ow circuit diagram illustrating a luidic control circuit in accordance with the invention;

FIGURE 2 is an electrical circuit diagram illustrating the manner in which the fluidic control circuit of FIG- URE 1 is energized;

FIGURE 3 is a graph illustrating control concepts of the invention and in particular the development of actuating signals in relation to position of the press stroke; and

FIGURE 4 is a flow circuit diagram similar to FIG- URE 1 also illustrating the fluidic control circuit of the invention.

Referring to the drawings, and in particular FIGURE 1, the uidic circuit is generally designated with the numeral 12. Shop air is provided to the circuit from a suitable source by means of inlet 14, passing through a plurality of conventional components to fluid input valves 16 and 18 positioned in series in the input line 20, designed to transmit input air to components 22 and 24, a PFF (Preference Flip-Flop) gate and an AND gate, re spectively.

The diamond arrowshaped symbol at the top of each gate indicates a supply fluid line attached to the gate. These lines are not shown in the drawings to avoid confusion of such lines with the control lines.

Referring to the PFF gate 22, this component produces an output at 02 with an input or signal at input connection C3. An input or signal at C1 or C2 will produce an output at 01. The output will remain at the appropriate port (01 or 02) even when the control signal is removed. This device is known as a bistable memory. The C1 input accomplishes the same function as the C2 input in this instance. The plus symbol in the 02 corner of the PPF v gate indicates that this is the preferred output connection.

The AND gate as shown is an active AND gate requiring a continuous iiuid supply at the top port, although it will be apparent to those skilled in the art that a passive AND gate could be used (as item 24 or in the place of other active AND gates in the circuit). The active and passive AND gates can be used in various combinations, but not all, can be passive. With no signals at C1 and C2, the output will be at 02. An output at 01 can only occur if both C1 and C2 have positive signals.

The active AND gate is usually made from three NOR gates, the components 26, 28 and 30 each being a NOR gate. The NOR gate has the uid power supply at the top, as with the other components hereinbefore mentioned, and an output will always be present at either 01 or 02 depending upon the signal condition at C1 (or other input connections of the NOR gate). With no signal at C1 or any other input connection, the output will be at 02. A positive signal at C1 or any input connection will switch the output from 02 to 01. When the signal at all input connections returns to zero the output will switch back to 02.

The active AND gate is produced from the three NOR gates (26, 28 and 30) in the following Way. The 02 output of either or both of two of the NOR gates 26 and 30 constitutes the input to the third NOR gate, item 28, either output causing an 01 output from the third NOR gate. To obtain an 02 output from the third NOR gate (item 28), both of the first two NOR gates 26 and 30 must have an input signal. In the absence of an input at either of the NOR gates 26 and 30, there will be no 01 output at NOR gate 28, or referring to AND gate item 24, in the absence of an input at either C1 or C2, there will be no 01 output.

Other items of the circuit requiring preliminary discussion are the interrupted Jet Sensor Limit Switches 32 and 34 (LS1 and LS2), and valves such as SC1, item 36. Concerning the LS switches, referring to LS1 and gate 2NOR (item 38), a signal will appear at input connection C1 of 2NOR to produce an 01 output as long as there is no obstruction in the open gap between connections (1) and (2) for LS1. The obstruction cam 40y permits a signal at input C1 for the period of the stroke when the crankshaft is between 90 and 270 (notice FIGURE 3). Similarly, the obstruction cam 41 for Limit Switch LS2 (34) permits a signal at input connection C1 of gate INOR (item 43) except for a small period of the stroke when the press crankshaft is at about 180 (FIGURE 3).

The valves SC simply open and close lines of the circuit in a conventional way.

It is desired that the circuit cause the press to perform a number of functions. For instance, it may be desired to have the press run continuously. Alternatively, it may be desired to have the press operate only on a single stroke basis, or the operator may wish to simply jog or inch the press forward through a 360 crank rotation. In addition, it is necessary that the operator be able to stop the press immediately in the event of an emergency, but normally it is desired to have the press stop at the top of its stroke. In the event of any failure in the control circuit, it is necessary to have the press stop, or in other words, for the circuit to fail safe.

All of these functions are provided in the following way. The press is provided in a conventional manner with brake and clutch mechanisms designed to cause the press crankshaft to move through a stroke and alternatively to come to a stop. These mechanisms are usually pneumatically actuated, and for the purpose of this disclosure, are

symbolically illustrated as a valve 42 for the clutch pneumatic mechanism and brake mechanism. A NOR gate 45 (identified as 9NOR) provides actuating ows to the valve 42, a 9NOR/01 ow actuating the clutch mechanism, a 9NOR/ 02 tlow actuating the brake mechanism. The 9NOR output is either at 01 or 02 so that when the clutch is actuated the brake is off, and vice versa.

To start the press (by actuating the clutch), there must be a signal at the C2 input of the 9NOR gate. This is provided from the output of 01/1AND (item 24), and can be termed the press Start signal. An input at both the C1 and C2 inputs of the IAND gate produces the 01 output. Valves 16 and 18 are normally open in branch conduit 20a of line 20 to provide a C2 input at IPPF gate (item 22), which in turn has an output at 01 providing a C1 input at IAND. As is characteristic of the 1PFF gate, termination of the C2 input does not disturb the 01 output, an 02 output occurring only through an input at C3. When the pushbuttons at 16 and 18 are both pushed, this provides a flow to the C2 input of IAND, which combined with the C1 input produces a 1AND/ 01 output and the desired Start signal. The pushbuttons 16 and 18 are spring loaded so that when they are released by the operator the C2/ 1AND input stops. This makes the Start signal or 1AND/01 output only momentary, or in existence as long as the buttons 16 and 18 are depressed.

The 9NOR gate has a C1 input as Well as a C2 input. The C2 input receives the momentary start signal from (b1/AND, and to keep the clutch engaged, there is provided a Run signal at the C1 input. Providing the C1 input or Run signal is a Latch-in AND gate, described generally above for the purpose of describing an AND gate, comprising gates 6NOR, 7NOR, and SNOR and generally designated with the numeral 50. As mentioned above an output from SNOR/ 02 required an input at both 6NOR and 7NOR, and the absence of an input at either of these gates results in a shifting ofthe output of gate SNOR from 02 to 01. To describe it another way, continuance of an input at C1/9NOR or continuance of the required Run signal to keep the clutch engaged requires an input at both 6NOR and 7NOR. Itis noticed that the output connection of 02/8NOR (line 46) in addition to having branch line 46a to C1/9NOR, has a branch line 46h recycling a portion of the output to the input connection C2 of gate 7NOR.

Initially, when 01/1AND was activated, it can be seen that the momentary Start signal was transmitted to connection C1/7NOR as Well as C2/ 9NOR. At the same time, a signal was received at C3/ 6NOR in a manner to be described, the two signals thereby activating the Latch-in AND gate. Recycle of a portion of the AND gate output of 02/8NOR effectively seals-in gate 7NOR and maintains an input at C1/9NOR. 'Ihe Run signal of C1! 9NOR continues until something occurs to interrupt the inputs to either GNOR or 7NOR.

The C3 input to gate 6NOR required for continuous running of the press is obtained in the following way. Providing this signal is a Seal-in AND gate generally designated with the numeral 48, made up of NOR gates SNOR, 4NOR and SNOR ( items 52, 54 and 56 respectively). The similarity of the configuration of these three gates to the Latchin AND gate or the active AND (also called Nor Logic) circuit should be evident, the seal-in gate also including a conduit 58 receiving an output flow from connection 02/5NOR, and a branch conduit 58b in flow communication with the input connection C2 of 4NOR, so that a portion of the AND gate output is recycled to the 4NOR gate to effectively seal-in the gate. In operation, the input connection C1 of gate 4NOR (54), along with the C1 and C2 input connections of gates 7NOR and 9NOR respectively, receives a lAND/ 01 output or Start signal initially in the start operation, producing an output at the 01 connection of 4NOR and no input at C2/ SNOR. Similarly, in a manner to be described, there is established an input at either of the C1 or C2 connections of gate 3NOR producing an 01 output at this gate, and no input at the C1 connection of gate SNOR. With no input at either C1 or C2 of gate SNOR, an output is established at the output connection 02 of this gate and in the conduit 58, which output is maintained by the portion of the output recycled to gate 4NOR, a branch 58a of the line 58 transmitting a portion of the flow to C3/6NOR.

During normal continuous operation of the press there will always be an input signal at gate 3NOR (item 52). In the absence of such an input, the output of gate SNOR would switch from 02 to 01. To obtain a C2 input at gate 3NOR, there is provided a gate 1NOR having input connection C1. A positive input ow produces an 01 output which is transmitted through valve SC1 (item 36) to the C2/3NOR input, as long as the SC1 valve is open or switched to CONT., its continuous operation position. Shifting the valve 36 to SING, meaning single cycle, terminates the input at C2/ 3NOR, Providing the C1 input at 1NOR is Limit Switch LS2 (34). Except when cam surface 40 is positioned between connections (1) and (2) of the Limit Switch, the signal input at C1 will exist. As mentioned above, the configuration of the cam 41 is such that the signal input at C1/ INOR will be interrupted for only a very short period, and referring to FIGURE 3, it can be seen that the cam is so linked with the press crankshaft that the signal interruption occurs when the press crankshaft is approximately at 180 To obtain a signal at the other input connection C1 of gate 3NOR, the connection is placed in flow communication 'with the output connection 01 of gate ZNOR (38) the latter receiving a signal from Limit Switch LS1. This Limit Switch is cammed, referring to FIGURE 3, to produce a signal at C1`/ 2NOR, and a 2NOR/ 01 output, when the press crankshaft is between 90 and 270, including the period when there is no input at the C2 connection of gate SNOR.

Accordingly, there will always be, during normal continuous operation of the press an input signal at either C1 or C2 of 3NOR. This coupled with the C2r/4NOR Seal-in input maintains the SNOR output at 02 and the input to C3/ 6NOR, or operation of the press.

The portion of the circuit including the gates 3NOR, 4NOR and SNOR, producing the C3 signal continuously at gate 6NOR, is what may be considered the memory portion of the circuit that logically remembers that the pushbuttons 16 and 18 'were depressed and that the mode of operation of the press is continuous. Even though the initial start signal to C2/ 9NOR was only momentary and terminated with release of the pushbuttons 16 and 18, the continuous input at C3/ 6NOR maintains the input at C2/ 9NOR causing the latter gate to maintain the 01 clutch output flow.

Should there be a power loss, the memory would self destruct and the press would automatically stop.

It should be noted that the 01 output of gate ZNOR (38) also produces a signal or input flow at the C1 input connection of gate 6NOR. For purposes of this application, this signal can be referred to as the Top-Stop signal, and as will be shown, the signal is used to bring the press to a normal stop at the top of its stroke, and is maintained for the necessary period to accomplish this function.

Providing an input at the C2 connection of gate 6NOR is gate ZPFF (item 62) from connection 01. This signal can be called a Repeat signal for reasons to be described. Actuation of the gate 2PFF to an 01 output is accomplished by an input at C2/4NOR obtained as a portion of the SNOR output, the input to gate ZPFF being through branch line 58C. As is characteristic of a PFF gate, the output will remain at 01 until switched to 02 by an input at connection C2. The latter connection is in ow communication with the 02 output of gate INOR (43), and the signal to C2/ ZPFF for reasons to be shown can be called the Anti-repeat signal.

At this point, two other items of importance should be mentioned, Emergency Stop Button (EMG) 64 and Top-Stop. button 66, the former being part of the Latch-in AND gate circuit 50, the latter part of what has been termed the Seal-in AND gate 48 comprising NOR gates 3NOR, 4NOR and SNOR.

The meaning of the terms Emergency Stop and Top- Stop should be self-evident, namely that the EMG button 64 brings the press to a stop anywhere in its cycle in the event of an emergency situation, the Top-Stop button bringing the press to a stop at the end or top of a stroke.

The emergency stop procedure is very simple, affected by pushing Emergency-Stop button 64. This interrupts the input to 7N OR (the release of start buttons 16 and y18 terminated the C1 input to this gate) producing Ian 02 output, and accordingly a C2 input at SNOR. Immediately, the output at `8NOR switches from 02 to 01 breaking the input at C1/9NOR, causing the output'at 9NOR to switch from 01 to 02. This deactivates the clutch mechanism and activates the brake mechanism at the same time, and brings the press immediately to a stop anywhere in the stroke cycle.

As the name implies, the emergency stop should only be used when personal injury or mechanical failure may result. Ordinarily it is desired that the press stop at the top of its cycle, since should it stop at the bottom it becomes very difficult to clear the press and continue operation.

A normal or Top stop is achieved by pushing Top- Stop button 66 interrupting the seal-in portion of the circuit 4S, namely terminating the C2 input to gate 4NOR. This shifts the output at SNOR from 02 to 01, thereby terminating the C3 -inp-ut to 6NOR. The C2 input at 6NOR may be maintained, at least for -a period of the stroke, since in the absence of a C2 input at the 2PFF gate, the output will remain at 01, even though the C1 input was interrupted by pushing button 66.

However, very quickly, at the 180 position of the press crankshaft, FIGUR-E 3, there lis a C2 input at ZPFF (from 02/1NOR in that C'I/INOR wa-s rmomentarily interrupted) shifting the output to 2PFF/02. Now, in the absence of a C1 input (SNOR being turned off) the output will remain at 02 termin-ating the C2 input to 6NOR.

Still the press will continue to run by virtue of the C1/ 6NOR input signal from 'LSL but as shown on FIG- URE 3, this is interrupted when thepress reaches about 270 by virtue of cam 40, bringing the press to a Stop at about 360 or the top of its stroke.

If the operator had pushed the Top-Stop button 66 when the press crankshaft was near the end of a stroke or beginning a new stroke, between the positions 270 and FIGURE 3, there would be no C1 input at 6NOR (LS1/2NOR lbeing turned olf) or C3 input. The press is carried through the next stroke to a Top-Stop position by a 2PFF/01 output and input at C2/6NOR or the Repeat signal, until this is turned-01T by the Antirepeat signal or 1NOR/02 output at about 180. The C1/6NOR Top-Stop input then stops the press at the top position in the usual manner.

The significance of the terms Repeat signal (C2/ 6NOR), Anti-repeat signal (C2/2PFF) and Top.. Stop signal (C1/6NOR) should be evident. On every cycle at about the switch L52 switches 1NOR to an 02 output momentarily, tending to trigger the `ZPFF gate to an 02 output. This is the Anti-repeat signal and in the absence of an output from the memory portion of the circuit (gates 3NOR, 4NOR and SNOR) which remembers that the start buttons were pressed, the press will be brought to a stop lby the Top-Stop signal at about 300. However, with an output from the memory gate, i.e. from OZ/SNOR, should the operator have delayed pushing the Top-Stop button past the 180 point, the

'C1 input at 2PFF will force the output to remain at 01.

Accordingly, even though the C3 and C1/'6NOR inputs are then terminated the press will repeat its stroke to come to a stop at the end of the next stroke.

The logic of the circuit can perhaps be better visualized from FIGURE 4 which shows gates 48 and 50 using the active AND gate configuration. The C2 input connection of gate 50 can be termed the emergency stop input connection and the C1 input connection can be termed the normal stop input connection. In the absence of an input at either connection the 9NOR gate switches from a clutch output to a brake output. Connected to the normal stop input connection C1 of gate 50 are 3 input sources, one for continuous running which remembers that the start pushbuttons were pressed |(AND gate 48), the other two being designed to maintain an input signal so that the press stops at a predetermined desired point in its stroke.

For single stroke operation, valves SCI and SC2 (36 and 65) are moved to the open position. This in effect removes BNOR, SNOR, 4NOR and ZPFF from the operating circuit. (See FIGURE 1.)

The press is started by depressing the run/jog pushbuttons 16 and 18V which along with 01/1PFF activates 01/1AND. The press will begin to stroke as soon as 01/1AND trips 01/9NOR. if the operator removes his hands from the run/jog push-buttons before the press reaches 90, the press will stop. After the press reaches 90, LS1 trips ZNOR and an input signal will appear at C1/6NOR. With inputs on 6NOR and 7NOR, OZ/SNOR will seal in C2/7NOR and the operator can remove his'hands from the pushbuttons. When the press reaches about 270, the signal from 01/2NOR 4will cease causing GNOR, 7NOR, SNOR and 9NOR to turn off. The press will then stop.

If the operator had held the push-buttons down, maintaining a signal at input C2/9NOR, the press would still :have stopped on top position because of the action of the anti-repeat signal. During the stroke, at about the 180 position, -LS2 causes a signal to result from 02/1NOR to C3/i1PFF. This will turn the memory oit killing 01/ IIAND, and thus the input at BNOR. The sequence for single stroke stopping would then be the same. Should the press coast beyond top position and on to 90, the press will not restart unless the operator react-ivates the run/ jog buttons.

An important safety aspect of the circuit should be mentioned. As previously indicated the PPF gates 22 and 62 have an initial or preferred output at the 02 output connections prior to the press being started or prior to an input signal. Thus, even though air is supplied to the diamonds of these gates from valve 80, the circuit will not assume an operator command not in fact directed by the operator. Should the ini-tial output from ZPFF, for instance, be at connection 01, the press would not stroke, but it would compromise the inherent safety provided -by the design. A Preference Flip-Flop gate can be replaced by two NOR gates in a manner well known to those skilled in the art.

Providing the C1 input to gate lPFF is valve 82 (R11) which is mechanically connected to valve 84 (1R12) in line 46 (the 02 output line of SNOR) so that when R11 is open R12 is closed and vice versa. A selector switch moves the valves between what can he termined Run and Jog positions. In the normal Run position R11 is closed (no iiow to C1/2PFF) and R12 is open, but if the operator desires to inch or jog the press forward, distinguished from single stroke or continuous operation, valve R11 is moved to its open position and R12 is closed. This provides a continuous C1 input to 1PFF and interrupts the output of SNOR, the latter step effectively remov-ing the seal in portions (3NOR-8NOR inclusive) from the circuit. Pressing the Run/Jog buttons 16 and 18 activates 1 AND to provide a C2/ 9NOR input, which is immediately -interrupted on release of the buttons, and the press stops in the absence of the signal from SNOR.

The Bar-Run switch 70 is normally in the run position to transmit shop air to the circuit via line 20, but in the bar position it turns off the press motor and engages the clutch to permit the operator to bar-move the press to desired positions.

In place of gate 9NOR, a PPF gate could be used with C1 and C2 input connections producing 01 clutch and 02 brake outputs respectively. The SNOR/ 02 output would be connected at the C1 input to produce the clutch signal, and the SNOR/ 01 output would be connected at the C2 input to produce the brake signal. The disadvantage is that should the C2 input be blocked there would be no way to stop the press. Accordingly, the use of a NOR gate is preferred.

FIGURE 2 simply illustrates a suitable electrical circuit. A three-phase input is supplied to the press motor 74, transformer 76 supplying a two-phase current to solenoid 78, the current actuating solenoid valve 80 in the air supply line.

Should any of the tubes connected to this iiuidic system be broken, the press would fail safe. If dirt blocks LS1 or LSZ, the press would stop.

It will be apparent to those skilled in the art that an aspect of the invention resides in a fluidic press control circuit in which the fail safe and emergency stop functions are generated by a lost signal conguration.

What is claimed is:

1. A uidic press control circuit which alternately activates a clutch mechanism and a brake mechanism comprising:

a uid gate including clutch and brake output connections and at least one input connection, an input producing an output iiow at the clutch connection;

an AND gate including an output connection in ow communication with the tiuid gate input connection, an input `at both of the input connections of the AND gate producing an output at the output connection thereof;

first recycle means connected to said AND gate output connection in ow communication with one of the AND gate input connections; to recycle a portion of the AND gate output to the AND gate input connection; v

means producing a signal at the other of said AND gate input connections;

stop means to interrupt the input to at least one of said AND gate input connections.

2. A circuit according to claim 1 wherein the first recycle means connected between the AND gate output connection and the AND gate input connection includes an emergency stop valve to interrupt the ow therein.

3. A circuit according to claim 2 further including means producing the signal to the other of said AND gate input connections responsive to the press crankshaft position, whereby the press can be stopped at a predetermined point in its stroke.

4. A circuit according to claim 1 wherein said AND gate includes iirst and second input connections and second input connection being in iiow communication with the output thereof, further including a second AND gate of the same configuration as said first mentioned AND gate including an output in flow communication with the iirst input connection of the first mentioned AND gate also including second recycle means in ow communication with an input connection of the second AND gate to recycle a portion of the second AND gate output to the second AND gate input connection:

emergency stop means to interrupt the recycle ow in said iirst recycle means;

means to interrupt the recycle ow in said second recycle means;

means to maintain a signal at the first mentioned AND gate first input connection until the press crankshaft reaches a predetermined position in its stroke.

5. A circuit according to claim 1 wherein said uid gate is a NOR gate.

6. A uidic press control circuit which alternately actition of the latch-in AND gate when the output of vates a clutch mechanism and a brake mechanism comthe seal-in AND gate is interrupted until the press prising: crankshaft reached a predetermined point in its a 9NOR gate including an 01 clutch output connection, stroke.

an 02 brake output connection, an input producing 5 9.A A control circuit according to claim 8 wherein said an 01 output; last-named means comprises a first signal means and a a first AND gate including 6NOR, 7NOR and SNOR second signal means both in flow communication with the gates, means to transmit the `SNOR/ 02 output to the first input connection of the latch-in AND gate;

one of said signal means constituting a top-stop signal means maintaining a iiow to said latch-in AND gate first input connection up to a predetermined point close to but prior to the press stroke top position the interruption of which causes the press to stop at the top of its stroke;

the other signal means constituting a repeat signal means the presence of which causes the press to continue operation despite interruption of the top-stop signal.

10. A control circuit according to claim 9 wherein said GNOR gate as an input thereat; 2() first and second recycle means to recycle portions of the 8NOR/02 and 5NOR/02 outputs respectively as inputs to 7NOR and 4NOR respectively; emergency stop means to interrupt the recycle iiow in said first recycle means; top-stop means to interrupt repeat signal means comprises a PPF gate including C1 and C2 input connections and 01 and 02 output connections, a C1 input producing an 01 output, a C2 input shifting the output to the 02 output connection and vice versa, the PFF gate 01 output being in flow communication with the latch-in AND gate first input connection;

the recycle fiow in said second recycle means; means to maintain an input to said 6NOR gate even after interrupting the iiow in said second recycle means until the press crankshaft is at a predetermined means to produce an anti-repeat signal at a predetermined point in the press troke at the C2/ PFF input connection to cause the output to shift from the 01 to the 02 .output connection;

position in its stroke.

7. A circuit according to claim -6 wherein said lastmentioned means comprises:

a first sensing device to produce a 6NOR gate input when the press crankshaft is between about 90 and about 270; 35

a ZPFF gate including 01 and 02 outputs responsive to C1 and C2 inputs respectively; means to transmit the PFF gate 01 output to said 6NOR gate as an input thereat;

means to transmit a portion of the SNOR/OZ output to the C1 input connection and the 2PFF gate;

a second sensing device to transmit a signal when the press crankshaft is at about 180 to the C2 input connection of the 2PFF gate;

the C1/ PFF input connection being in fluid communication with the seal-in AND gate output connection whereby the shift from CZ/PFF 01 to 02 occurs only in the absence of the seal-in AND gate output.

11. A control circuit according to claim 10 wherein both said signal means include jet-sensor limit switches with cam means connected to the press stroke designed to produce the signals thereof at predetermined points.

12. A control circuit according to claim 10 wherein the seal-in AND gate first input connection receives a signal at all times during press operation from one of said signal means in continuous mode operation.

13. A iiuidic press circuit according to claim 12 wherein said repeat signal means comprises a jet sensor limit switch;

the output of the `2PFF gate transferring to the 02 -munication with the NOR gate input connections, an input at both the input connections of the AND gate producing an output at the output connection thereof;

first recycle means connected to said AND gate output connection in ow communication with said second input connection of said AND gate, said recycle means including emergency stop means to interrupt the flow therein;

a second NOR gate including an input connection and connection in the absence of an 02 output from the 45 01 and 02 output connections, an input producing an SNOR gate. 01 output;

8. A iluidic press control circuit which alternately means COInnlnniCaiing the let SenSOl limit SWiCh With activates a clutch mechanism and a brake mechanism the NOR gaie inPnt, the 02 On'fPnt being in fiOW Colncgmprising; munication with the CZ/PFF input connection, the

a NOR gate including clutch and brake output con- 91 Output being in HOW Communication With the firSt nections and an input connection, an input proinput connnniinn 0f the Seal-in AND gate;

ducng an output ow at the clutch connection; cam surface means connected to the press stroke intera latch-in AND gate including first and second input fnnnng the C1 inPllt 0f in@ NOR gaie Causing a CZ/PFF connections and an output connection in iiow com- Input;

14. A control circuit according to claim 13 wherein said 01/NOR output is blocked for single stroke operation of the press;

said top-signal means producing an input at the latchin AND gate first input connection and at the seal-in AND gate rst input connection for about the portion of the stroke from 90 to about 270;

a seal-in AND gate including first and second input an anti-repeat signal from the second signal means to connections and an output connection in fiow com- CZ/PFF maintaining an input at the first input conmunication with the first input connection of said nection of the latch-in AND gate to cause the stroke latch-in AND gate, an input at both the input conto continue to its top position. nections of the seal-in AND gate producing an 15. A control circuit according to claim 12 wherein said output at the output connection thereof; repeat signal means comprises:

second recycle means connected to said seal-in AND gate output connection in ow communication with the first input connection thereof including top-stop means to interrupt said input;

means to maintain a signal at the first input connecsive to a positive input and an 02 output connection responsive to no input; n

rst means transmitting said 01 output to the seal-in AND gate first input connection;

second means transmitting the 02 output to C2 input connection of the PFF gate;

means to interrupt the flow in said iirst means or single stroke operation.

16. A liuidic press control circuit which alternately activates a clutch mechanism and a brake mechanism comprising:

a NOR gate including clutch and brake output connections and an input connection, an input producing an output iiow at the clutch connection;

iirst AND gate means including first and second input connections and an output responsive to inputs at both said input connections;

means transmitting the AND gate means output to the NOR gate input connection;

emergency stop means to interrupt the input to the second of said AND gate input connections, said input being a portion of the AND gate means output ow;

second AND gate means including first and second input connections and an output connection in flow l communication with the other of said iirst AND gate means input connections, an input at both the input connections of said second AND gate means producing an output at said output connection;

start signal means providing an input flow to the second input connection of said second AND gate;

said start signal means comprising a third AND gate including iirst and second input connections, an output responsive to an input at both the input connections thereof;

spring-loaded valve means supplying a flow to the second of said third AND gate input connections whereby the output of said third AND gate is maintained as long as the valve means is held open;

means to recycle a portion of the second AND gate output to the second input connection thereof to maintain an input at said connection even when said valve means is closed terminating said start-signal.

17. A circuit according to claim 16 including means to interrupt the portion of the second AND gate output flow recycled to the second input connection thereof.

1S. A iiuidic press control circiut comprising:

tirst and second switch means including tirst and second cam means to interrupt the output How therefrom;

rst and second NOR gates including input connections in flow communication with said switch means outputs respectively, further including 01 and 02 output connections, in input producing an 01 output;

a latch-in AND gate including first and second input connections, a positive input at both said input connections producing an output;

means communicating the iirst NOR gate 01 connection with said latch-in AND gate iirst input connection, said tirst cam means interrupting the ow at a predetermined first point in the press cycle;

a seal-in AND gate also including rst and second input i connections, a positive input at both said input connections producing an output;

said first NOR gate 01 connection also being in communication with said seal-in AND gate lirst input connection;

means communicating the second NOR gate 01 connections with said seal-in AND gate first input connection;

anti-repeat signal means communicating the second NOR gate 02 connection `with said latch-in AND gate first input connection including a PFF gate and an 01 output therefrom in communication with s'aid rst input connection;

means communicating the seal-in AND gate output with said PFF gate whereby the AND gate output produces at latch-in AND gate input;

the 02 signal from said second NOR gate interrupting the input to said latch-in AND gate when the sealin AND gate output is terminated;

said second cam means resulting in an 02 signal from said second NOR gate at a point in the press cycle earlier than said first-mentioned point.

19. A uidic press control circuit comprising:

a fluid gate including 01 and 02 output connections and at least one input connection to producean 01 output;

start signal means to provide at least a momentary iiow to said input connection;

memory circuit means responsive to said start signal means ilow to produce a continuous iiow to said input connection;

said start signal means comprising and AND gate including C1 and C2 input connections and an 01 output connection producing said liow;

a second gate including an 01 output connection in dow communication withsaid AND gate C1 input connectio-n;

first, second and third fluid input lines, the second and third input lines being connected to said second gate to produce said 01 output, the first line being connected to the AND gate C2 input connection;

iirst, second and third valve means in said input lines;

a fourth valve means in said memory circuit means to interrupt said continuous ow;

a iirst selector switch to alternatively open and close said first and second valve means;

a second selector switch to alternatively open and close said third and fourth Valve means whereby when said memory circuit means continuous ow is interrupted, the press can be inched forward by closing said first Valve means.

References Cited UNITED STATES PATENTS BILLY I. WILHITE, Primary Examiner U.S. Cl. XR.

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