DE2917949A1 - Protective circuit for stamping tool - has hydraulic cylinder and feed mechanism and relay switching circuit controlling hydraulic cylinder operation - Google Patents

Abstract

The protective circuit is for a stamping machine, which prevents a stamping stroke in the absence of the punching tool, has a punching table for the stamping. The pressure plate is linked to a hydraulic cylinder and a feed mechanism. The stamping stroke of the hydraulic cylinder is electrically controlled by a relay, which releases the trigger. The relay is operated by a pedal switch. The current circuit of the release relay incorporates the switching contacts of another relay. This relay is operated by a switch with contacts operated via the underside of the pressure plate.

Description

Protective circuit on punching machines

The invention relates to a punching machine according to the preamble of Claim t.

In known punching machines with a punching table, one by means of a Hydraulic cylinder up and down movable pressure plate and one on the material to be cut Free-lying punching knife begins a punching process with the pressure plate first from top dead center via a pedal and a linkage against the force of a Return spring is pushed downwards. If the operator during the Punching process holds the material to be punched with her hands, the hydraulic cylinder can The punching stroke to be carried out is not due to the two-hand trigger that is otherwise common for safety reasons be switched on, but is triggered by the pedal used for lowering. In order to avoid accidents, a special switching measure prevents that the punching stroke is triggered too early. As long as the pressure plate with the low force downward movement a distance of more than 12 mm to the Has punching knife, the punching stroke cannot be performed. As soon as the pressure plate has reached a distance of 12 mm from the knife and is therefore so close to the knife has approximated that the operator is no longer between the printing plate and the Can grip the punching knife, a limit switch called a 12 mm switch is actuated, which releases the triggering of the punching stroke, but without this already to this Time to switch on. The punching stroke is only activated by a second limit switch triggered, the switching time is adjusted so that it is approximately with the touchdown of the pressure plate collapses on the punching knife.

The lowering of the pressure plate and the triggering and execution of the punching stroke take place regardless of whether a punching knife is on the material to be punched or is missing. With a punch knife there is no danger for the operator to himself to be able to injure in case of inattentiveness. If, on the other hand, there is no punching knife on the material to be punched, so the operator can reach into the space that normally is filled in by the punching knife. There is a risk that the punching stroke executing pressure plate a hand in the punching room due to inattentiveness the operator presses and squeezes against the material to be punched.

The invention is based on the object of a punching machine the preamble of claim 1 & u create where it is excluded is that if the punching knife is missing, a punching stroke can take place. This job is solved by the specified in the characterizing part of claim 1 features.

By placing an additional switch in the circuit of the relay that triggers the punching stroke and the measure to design this switch so that its contacts of mutually insulated conductor tracks one on the bottom of the pressure plate attached contact plate are formed and its switching bridge formed by the metallic and therefore electrically conductive back of the punching knife is, it is achieved that a punching stroke can only be carried out when the Contact plate touches the punch knife and thereby the conductor tracks of the contact plate be short-circuited. On the other hand, does not read a punch knife on the material to be punched and will accidentally moves the platen down by means of the feed mechanism1 so no punching stroke can be triggered even after pressing the 12 mm switch, because the conductor tracks of the contact plate are not short-circuited if the punch knife is missing are interrupted and therefore the circuit of the trigger relay switching on the punching stroke remain. In this way it is ensured that even if the punching knife is missing, any Risk of injury is excluded.

According to a further proposal of the invention are in the circuit of the trigger relay contain switching contacts of a relay of a monitoring circuit, which has at least switching contacts of a further relay, which is not at short-circuited contacts of the contact plate is switched through.

With the help of the monitoring circuit at the beginning of a punching process the correct switching status of the contact plate before lowering the pressure plate comprehensive switch and the associated relay checked. Provided the contacts the contact plate lifted off the punch knife is not properly short-circuited are, the switchable via the contact plate relay is switched through, whereby whose switching contacts located in the monitoring circuit are closed. Consequently the monitoring circuit is also closed, whereby its relay switches through, which closes its switching contacts located in the circuit of the trip relay. That Closing of the switching contacts of the relay lying in the monitoring circuit is Prerequisite for the later triggering of the punching stroke.

On the other hand, it is through in the contact plate lifted off the punching knife Damage or a fault a short circuit has occurred, this is via the contact plate switchable relay dropped out, causing its lying in the monitoring circuit Switching contacts remain open. As a result, the monitoring circuit also remains open, which means that its relay remains de-energized. If the relay in the monitoring circuit has dropped out if its switching contacts in the circuit of the trip relay remain open, which means that when the pressure plate is lowered, no punching stroke can be carried out. To this Way is with a defective contact plate by a short circuit with certainty avoids a punching stroke endangering the operator in the absence of a punching knife can be triggered.

In the same way as through the monitoring circuit the proper one The switch state of the switch comprising the contact plate can be checked by a corresponding expansion of the monitoring circuit also determine whether other switches and relays are in the proper starting position. Is this because of mechanical, for example Defective limit switches or so-called sticking of the relay contacts is not the case, the corresponding switching contacts in the monitoring circuit remain open, so that this also remains open. With the monitoring circuit left open the execution of a punching stroke is prevented, so that also in this case none Risk of injury to the operator or the risk of damage to the Machine exists.

The invention is illustrated by the following description of one in the Drawing illustrated embodiment explained in more detail.

1 shows a partially sectioned view of a punching machine with a schematically illustrated pneumatic and hydraulic circuit diagram; Fig. 2 a electrical circuit diagram, with the switching status when the machine is switched on, but is shown not yet actuated foot switch, and FIG. 3 is a view of the underside the contact plate.

The punching machine has a C-shaped frame 1 and a height-adjustable one Punching table 2 for receiving the punched material G on.

On the punched material G is made of metal and therefore electrical conductive punch knife 3.

At the upper end of the frame 1, a housing 4 is attached, which for Recording of a plate 5 and a guide bush 6 existing up and movable pressure plate 7 is used. On the housing 4 is this one that closes at the top Cover plate 8 attached. In the cover plate 8 are two double-acting pneumatic cylinders 9, 10 attached, the piston rods 119 12 with the guide bush 6 of the pressure plate 7 are firmly connected. A cam 13 is located on the outside of the guide bush 6 arranged, the one arranged on the housing 4, as a so-called 12 mm switch b3 designated limit switch interacts.

The piston rod 14 of a piston 15 is attached to the cover plate 8 The piston rod 14 and the piston 15 are provided with a longitudinal bore 16 which opens at the lower end face of the piston 15. The upper opening of the longitudinal hole 16 is connected to a pressure line 17. The stationary piston 15 contributes that can be moved up and down and at the same time relative to the guide bushing 6 of the pressure plate 7 displaceable cylinder housing 18 of a double-acting hydraulic cylinder 19. On the cover of the cylinder housing 18 there is an inside of the cylinder housing 18 opening pipe 20 that can be moved up and down with this is attached. The tube 20 is passed through the cover plate 8 and connected to a pressure line 21. A cam 22 is arranged on the tube 20, which cam is connected to the top dead center of the cylinder housing 18 associated limit switch bl and an adjustable lower dead center Limit switch b2 interacts. The limit switches bl, b2 are on one on the cover plate 8 attached carrier 23 is arranged.

The two pressure lines 17.21 are connected to a 4/3-way valve 24, its middle switch position by spring force, its right switch position by a solenoid St and its left switching position shown in Fig. 1 by a solenoid S2 is switched. In the left switching position shown in FIG a pump 25 presses oil sucked in from a reservoir 26 into the pressure line 21 and thus on the top of the piston 15, whereby the cylinder housing 18 in the top dead center is held. This is located in below the piston 15 Space of the cylinder housing 18 contained oil via the pressure line 17 into the reservoir 26 returned.

The two pneumatic cylinders 9, 10 are each with one at the upper end the cylinder opening common pressure line 27 and each one on the lower sand the cylinder opening common pressure line 28 is connected. The pressure line 27 is connected to a 3/2-way valve 29, the switching position of which is shown in FIG switched by a Schaltmagaet S3 and its left switching position by spring force will. The pressure line 28 has a adjustable throttle valve 30 and is connected to the pressure line 27 upstream of the directional control valve 29. The two Pressure lines 27, 28 are connected to a compressed air source 31.

According to the circuit diagram shown in FIG. 2, the pump 25 driving motor 32 of three-phase alternating current (lines R, S, T, Mp) via a Main switch 33 fed. The control circuit for the electromagnetically operated Directional control valves 24, 29 is fed with alternating current low voltage, while the Switching solenoids S1, S2, S3 with direct current generated by a rectifier circuit 34 operate.

The limit switch is in a circuit 35 of the control circuit bl included, which is located by the cylinder housing 18 in the top dead center Cam 22 is open and closed by spring force when the cam 22 is removed. The circuit 35 also contains a relay D1. In a circuit 36 is the end switch b2 determining the bottom dead center of the cylinder housing 18 is arranged, which is opened by spring force when the cam 22 is removed. In circuit 36 is also contain a relay D2. In a circuit 37 it is a 12 mm switch designated limit switch b3 arranged, which cooperates with the cam 13 and at remote cam 13 is opened by spring force. In circuit 37 is also a relay D3 included.

In a circuit 38 are a spring force in the open position held foot switch b4 and a relay D4 included.

In a circuit 39, a switch b5 is arranged, its contacts of two in a contact plate fastened to the underside of the pressure plate 7 44 arranged, mutually insulated, comb-like conductor tracks 45, 46 (Fig. 3) are formed. The switching bridge assigned to the conductor tracks 45, 46 is formed by the metallic back of the punch knife 3. In circuit 39 is also contain a relay D8. In a circuit 40 are a relay D9 and normally closed contacts d8 of the relay D8 arranged. In a circuit 41, the contacts 47, 48 are one changeover switch d9 actuated by relay D9 included, as well as working contacts d3.1 of relay D3, normally open contacts d4.2 of relay D4, normally closed contacts d5.2 of one Relay D5, normally open contacts dlO.1 of a relay DiOl rest contacts d2.1 of relay D2 and a relay D6 called a trip relay. The circuit 41 also includes a self-holding contact d6.3 of the trip relay bridging the normally closed contacts d5.2 D6. The contacts 47, 49 of the aforementioned changeover switch are in a circuit 42 d9 and a relay D10 are arranged.

In a circuit 43 called a monitoring circuit Normally closed contacts d2.2 of relay D2, normally closed contacts dl of relay Dl, normally closed contacts d6.4 of the trip relay D6, normally closed contacts d3.2 of the relay D3, normally closed contacts d4.3 of the relay D4 and normally closed contacts dz0.2 of the relay D10 are arranged. The monitoring circuit 43 also contains a relay D5 and one of the last four rest contacts bridging self-holding contact d5.3 of relay D5.

In a circuit 50 are normally closed contacts d5.1 of the relay D5 from the Monitoring circuit 43, make contacts d4.1 of relay D4 and a switching magnet S3 of the directional control valve 29 included. In a circuit 51 are normally open contacts d6.1 of the trigger relay D6 and a switching magnet St of the directional control valve 24 are included. In one Circuit 52 are normally closed contacts d6.2 of the trip relay D6 and a switching magnet S2 of the directional control valve 24 is arranged.

The punching machine works as follows: By pressing the main switch 33, the motor 32 is switched on, which drives the pump 25. At this time the directional control valve 24 is in the middle position, so that the pump 25 turns it off The oil sucked in the reservoir 26 is immediately fed back into it. That Directional control valve 29 is in the position shown in FIG. 1, in which the pressure lines 28 connected to the compressed air source 31, while the pressure lines 27 blocked are. In this position of the directional control valve 29, the pneumatic cylinders 9, 10 hold the Pressure plate 7 in a raised position.

Provided all relays and switches are in good working order, the The following initial situation arises before the start of a punching process.

The limit switch assigned to the top dead center of the cylinder housing 18 bl is opened by the cam 22, whereby the relay D1 has dropped out and its Normally closed contacts dl in the monitoring circuit 43 are closed. The one below Dead center of the cylinder housing 18 determining limit switch b2 is open because the cam 22 assigned to it is removed. As a result, the relay D2 has dropped out. Its normally closed contacts d2.1 in circuit 41 and normally closed contacts d2.2 in the monitoring circuit 43 are closed. The 12 mm switch b3 is open because the cam 13 is still one Distance from him. Therefore the relay D3 has dropped out. His working contacts d3.1 in circuit 41 are open, while the normally closed contacts d3.2 in the monitoring circuit 43 are closed. Before the start of a punching process, the foot switch b4 is open and thereby the relay D4 dropped out. As a result, the working contacts are d4.1 in circuit 50 and the normally open contacts d4.2 in circuit 41 open while the normally closed contacts d4.3 in the monitoring circuit 43 are closed.

Since the contact plate 44 is removed from the punch knife 3, the conductor tracks are 45, 46 not shorted. Therefore, the switch including the contact plate 44 is b5 opened in circuit 39, whereby the relay D8 has dropped out. Here are the normally closed contacts d8 in the circuit 40 closed, so that the relay D9 is switched through is. When relay D9 is switched through, its changeover switch d9 holds contacts 47, 49 of the circuit 42 closed, whereby the relay D10 is switched through. When the relay D10 is switched through, its working contacts d10.1 are in the circuit 41 open and its normally closed contacts d10.2 in the monitoring circuit 43 closed. As long as the changeover switch d9 keeps the circuit 42 closed, the contacts are 47, 48 in the circuit 4i forcibly open, so that the relay D6 has dropped out. This has the consequence that the normally open contacts d6.1 in the circuit 51 are opened Normally closed contacts d6.2 in circuit 52 closed, the self-holding contact d6.3 open in circuit 41 and the normally closed contacts d6.4 in the monitoring circuit 43 are closed.

So after all the normally closed contacts in the monitoring circuit 43 are closed, the relay D5 is switched through, which has the consequence that Normally closed contacts d5.1 in circuit 50, the normally closed contacts d5.2 in circuit 41 and the Latching contact d5.3 in the monitoring circuit 43 are closed. So is created the prerequisites for initiating a punching process.

Each punching process is initiated by closing the foot switch b4. The closing of b4 has the consequence that the relay D4 switches through and its normally open contacts d4.1 in circuit 50 and the normally open contacts d4.2 in circuit 41 are closed and the normally closed contacts d4.3 in the monitoring circuit 43 are opened. Because in the monitoring circuit 43 the self-holding contact d5.3 is closed, the relay D5 remains when opening the normally closed contacts d4.3 switched through. By closing the working contacts d4.1 the circuit 50 is closed, whereby the switching magnet S3 the directional control valve 29 switches. This has the consequence that over the pressure lines 27, 28 both the top as well as the underside of the pistons 55, 56 of the pneumatic cylinders 9, 10 with compressed air be applied. Because the bottom of each piston 55, 56 because of the piston rods 11 or 12 has a slightly smaller area than the top, the predominates Force acting on the top of the pistons 55, 56, causing the pneumatic cylinders 9, 10 move the pressure plate 7 downwards with little overall force.

When the pressure plate 7 reaches a distance of 12 mm from the punching knife 3 has, the cam 13 actuates the 12 mm switch b3, whereupon the relay D3 switches through. As a result, the working contacts d3.1 in the circuit 41 are closed and the normally closed contacts d3.2 in the monitoring circuit are open.

As the lowering of the pressure plate 7 continues, it settles the contact plate 44 on the back of the punch knife 3, whereby the conductor tracks 45, 46 are short-circuited via the punch knife 3. By short-circuiting the conductor tracks 45, 46 or closing the switch b5, the circuit 39 is closed, whereby the relay D8 switches through and its normally closed contacts d8 in the circuit 40 open will. This has the consequence that the relay D9 drops out and its changeover switch d9 the Contacts 47, 49 in circuit 42 opens and contacts 47, 48 in circuit 41 closes. By opening the circuit 2, the relay D10 drops out, while the normally open contacts d10.1 closed in circuit 41 and the normally closed contacts dlO.2 in the monitoring circuit 43 can be opened.

After the contacts 47, 48 and the working contacts dlO.1 closed are, thus all contacts in the circuit 41 are closed, so that the trip relay D6 switches through. As a result, the normally open contacts d6.1 in the circuit 51 closed, the normally closed contacts d6.2 in the circuit 52 open, the self-holding contact # d6.3 closed and the normally closed contacts d6.4 in the monitoring circuit 3 are opened.

The switching magnet switches when the normally open contacts d6.1 are closed S1 the directional control valve 24 from the middle position to the right switching position, whereupon the pump 25 presses oil through the pressure line 17 onto the underside of the piston 15. As a result, the cylinder housing 18 performs a downward punching stroke off, initially following the already lowered pressure plate 7, then itself sits on him and then over the pressure plate 7 the punching knife 3 into the material to be cut G presses.

As the cylinder housing 18 is lowered, the cam 22 moves away from the Limit switch bl, whereupon the relay D1 switches through. This has the consequence that the Normally closed contacts dl in the monitoring circuit 43 and thus also this is opened. When relay D5 drops out, its normally closed contacts d5.1 also open in the circuit 50, d5.2 in circuit 41 and the self-holding contact d5.3. Since the normally closed contacts d5.2 but through the self-holding contact d6.3 will be bridged the punching stroke of the cylinder housing 18 is not interrupted. The punching stroke will be so long executed until the cam 22 the limit switch determining the bottom dead center b2 actuated. By closing the limit switch b2, the relay D2 switches through what has the consequence that the normally closed contacts d2.1 in the circuit 41 and d2.2 in the monitoring circuit 43 can be opened. When the normally closed contacts d2.1 open, the tripping relay D6 drops from, whereupon the previously closed normally open contacts d6.1 in circuit 51 are opened and the previously opened normally closed contacts d6.2 in the circuit 52 are closed. As a result, the directional control valve 24 is in the left switching position shown in FIG. 1 switched, whereupon the pump 25 oil through the pressure line 21 to the top of the Piston 15 pushes and thereby lifts cylinder housing 18 from bottom dead center. Since the normally closed contacts d5.1 in circuit 50 have already been opened, the switching magnet has S3 the directional control valve 29 is switched back to the switching position shown in FIG. 1, so that the pressure plate 7 follows the cylinder housing 18 moving upwards.

When the release relay D6 releases, the self-holding contact d6.3 opened and the previously opened normally closed contacts d6.4 in the monitoring circuit become 43 closed again. As soon as the cylinder housing 18 and the pressure plate 7 their have reached top dead center and the foot switch b4 is not actuated, dlle Switches and relays resumed their initial position shown in the circuit diagram, all of the normally closed contacts in the monitoring circuit 43 are closed again.

As follows from the above, the cylinder housing 18 only execute the punching stroke when the conductor tracks 45, 46 of the contact plate 44 are short-circuited via the punch knife 3 and, as a result, via the relay D8, D9 and D10 the circuit 41 of the trip relay D6 is closed.

If, for example, the conductor tracks 45, 46 also from the punching knife 3 lifted contact plate 44 are short-circuited due to a defect, is before the start of a punching process and before pressing the foot switch b4 the circuit 39 is closed and thereby the relay D8 is switched through. at When relay D8 is switched through, its normally closed contacts 48 are open, causing the relay D9 has dropped out. Here, circuit 42 is opened via switch d9, whereby the relay D10 has also dropped out. When relay D10 has dropped out, whose normally closed contacts dz0,2 in the monitoring circuit 43 open, which results in has that the monitoring circuit 43 cannot be closed.

When relay D5 has dropped out, the normally closed contacts d5.1 are in the circuit 50 opened, so that when the foot switch b4 is pressed, the circuit 50 of the switching magnet S3 cannot be closed.

In the event of a short circuit in the contact plate caused by a defect 44 thus causes the monitoring circuit 43 that the punching machine is not in operation can be set.

With the help of the monitoring circuit 43, the proper Checked the starting position of the remaining switches and relays before starting a punching process. If, for example, the 12 mm switch b3 is not actuated as a result of a If the defect is closed, the corresponding one is already in place before the start of a punching process Relay D3 closed. When relay D3 is closed, it is in the monitoring circuit 43 lying rest contacts d3.2 open, so that the monitoring circuit 43 does not can be closed. This in turn has the consequence that the normally closed contacts d5.1 are open in circuit 50 and this cannot be closed. Therefore the punching machine cannot be put into operation in this case either.

Claims (2)

Claims b punching machine with a punching table for recording of the material to be cut, a cutting knife resting on the material to be cut, an up and movable, connected to a feed mechanism and a hydraulic cylinder Pressure plate and an electrical circuit to control the punching stroke of the hydraulic cylinder with a relay that triggers the punching stroke and has switching contacts in its circuit a relay that can be actuated by a foot switch, as well as switching contacts one through a so-called 12 mm switch actuatable relay are included, characterized in that, that in the circuit (41) of the release relay (D6) switching contacts (d9) of a relay (D9) are included, which can be actuated by a switch (b5), its contacts of two in a contact plate attached to the underside of the pressure plate (7) (44) arranged, mutually insulated conductor tracks (45, 46) are formed and whose switching bridge is formed by the metallic back of the punching knife (3). 2. Punching machine according to claim 1, characterized in that im Circuit (41) of the trigger relay (D6) switching contacts (d5.2) of a relay (D5} of a Monitoring circuit (43) are included, the at least switching contacts (d 10.2) of a relay (DIo) which, if the contacts are not short-circuited (45, 46) of the contact plate (44) is durchge # cha1-tet.