DE1033763B - Automatic electrical control circuit for pressing, punching or the like. - Google Patents

Description

The invention relates to an automatic electrical control circuit for pressing, punching or the like Machine tools.

There are already cutting presses, hole cutting and punching machines known, each with a electrically conductive organ equipped workpiece carrier or table and boom, of which the latter is arranged to move up and down with respect to the workpiece table lets to place on a cutting or punching tool during its downward movement and the same through to drive the workpiece on the table. There is a drive for the lifting movement of the boom provided for the initiation of the working stroke, d. H. the downward movement of the boom to the workpiece table is put into operation by a control unit. Furthermore, a control is provided here, when closing one after the boom has moved downwards over the latter, the Tool and the workpiece table forming electrical circuit the working stroke, so the Downward movement of the boom towards the workpiece table can end. Thus, the working stroke of the boom regardless of the thickness of the workpiece or the height of the cutting, punching or other, z. B. at Die used tool can be controlled.

According to the invention, a control circuit is now provided in which the response of the control for the termination of the working stroke with a certain stroke position of the tool, for example the first contact part of the latter with the workpiece carrier, in a fixed time relationship and with such a delay occurs that all parts of the tool penetrate the workpiece and with the Workpiece carriers can come into contact before the working stroke of the boom and its direction of movement have ended is reversed. The length of time between when the tool first touched the Workpiece carrier and the complete penetration of all cutting edges of the tool through the workpiece and the resulting termination of the working stroke is different and depends z. B. the nature of the respective workpiece material. Taking this into account and for the purpose of compensation the possible differences in the operating speed of the drive of the machine tool in question the control must respond to the end of the working stroke with one after the first Contact of the hitting parts can be delayed, which can be changed can, however, regardless of the contact resistance between those in contact with each other stepping parts and the resistance must be their supply lines.

Automatic electrical control circuit
for pressing, punching or the like.

Applicant:

United Shoe Machinery Corporation,

Flemington, N.J., and Boston, Mass.

(V. St. A.)

Representative: Dipl.-Ing. A. Bohr, Munich 5,

Dr.-Ing. H. Fincke, Berlin-Lichterfelde,

and Dipl.-Ing. H. Bohr, Munich 5, Müllerstr. 31,

Patent attorneys

Claimed priority:
V. St. v. America January 13th and February 11th 1955

Roy Gustaf Ericson, Danvers, Mass.,

Frank Earl Stratton, Beverly, Mass.,

and Robert Whitney Bradley, Marblehead, Mass.

(V. St. A.),
have been named as inventors

The control circuit for the termination of the working stroke according to the invention leaves these conditions with the highest possible accuracy, reliability and economy.

Furthermore, the control circuit according to the invention ensures an intermediate response between the two and delay in the actual control process caused by individual differences different work processes is independent and to adapt to that of the respective machine tool inherent delays can be minimized.

For this purpose, the control circuit for the termination of the working stroke according to the invention has one Relay circuit with a DC input stage that contains a grid-controlled gas discharge tube. This tube receives in the normal state from a DC voltage source with one in series with it lying resistance, which has essentially only one active component, a bias voltage in which she locks. The DC voltage source is on the one hand 'to

809 560/354

the input electrodes of this tube, on the other hand to the electrically conductive elements of the workpiece table and the cantilever connected in parallel, so that the resistance between these organs with the series resistance the DC voltage source forms a voltage divider. This is the effective grid bias of the tube is always proportional to the resistance between the said organs when it is reduced below a predetermined resistance value to the voltage limit value at which the tube ignites and thus becomes conductive, even if the resistance of the conduction path assumes a considerable size from one organ to the other including the relevant supply lines. So when the boom and workpiece table are connected to the terminals of the DC voltage source are, consequently the contact of the tool with the two aforementioned organs causes the tube becomes conductive, regardless of the time of the size of the thus in the shunt of the voltage source lying resistance, provided, however, that the resistance value of this resistor is below the the values corresponding to the voltage limit. This is especially important when for the senior Organ of the tool table a material of the type conductive rubber is used, which has a considerable and under different working conditions of the tool variable resistance between the touching points of the governing bodies.

According to a further feature of the invention is in the output circuit of the above-mentioned tube Circuit switched with a time constant that can be changed by appropriate setting, so that the Output voltage of this circuit and consequently its delay effect as a result Isolation of the DC input stage from changes. Of resistance between the touching ones Organs is independent. By using a DC voltage in the input stage there are also fluctuations occurring due to the non-uniformity of the AC voltage source avoided.

According to a further embodiment of the invention, a control circuit can be changed over time Delay using two gas discharge tubes in a two-stage control circuit provided, which is a switching element connected between the two stages with a variable time constant and a relay connected to the output circuit of the second stage. With this circuit Not only does the time constant term remain unaffected by external influences from the previous stage, but the time delay caused by the control circuit is also independent of the variable Properties of the relay, such as B. the response friction of an armature, the response time can change if, for example, the closing time of the relay from the controlled increase in the relay winding current is made dependent.

The invention also offers a further possibility, as a two-stage, for ending the Working stroke provided control circuit with a usually conductive AC output stage which interrupts its current when a discharge occurs in a tube in the input circuit, so that after a predetermined period of time after the onset of this discharge, the actuation to bring about a relay. This ensures that the initiation of a working stroke only occurs can if the emission of the output tubes is sufficient. In addition, the winding of the lying in the output circuit relay bridging discharge elements, z. B. tubes, be provided, which ignite if the output circuit is interrupted in order to accelerate the opening of the relay.

Finally, according to the invention, a fuse is created in the control circuit to prevent injuries the operator can avoid, in the event that the boom on the way of its working stroke on a part of the body, z. B. a finger, des Worker meets, even if there is insulating material between this body part and the concerned governing body. According to the invention, the worker with the one is responsible for this security Hand to turn on the boom drive operated handle with the workpiece table and therefore electrically connected to the control circuit, so that when the boom hits part of the the other hand of the worker during the working stroke the input voltage of the control circuit in this way is changed so that the latter can terminate the working stroke of the boom immediately.

In the drawings are two exemplary embodiments the control circuit according to the invention illustrated schematically.

Fig. 1 shows a circuit diagram for a cutting press according to the invention;

Fig. 2 shows the circuit diagram in another embodiment.

The cutting press shown in Fig. 1 has a workpiece table 10 which is covered with a workpiece support plate 12 made of an electrically conductive material, for example conductive rubber, on which the plate or sheet material, for. B. leather, fabric or the like., Existing workpiece 14 rests in order to be processed by the cut * or punching tool freely resting on it, eg. B. to be punched out. A fully on its underside with a metallic, electrically conductive face plate 19 ¹ -statteter boom 18 is in a next to the plant * - piece support 10 provided for the vertical column 20 pivotally mounted and can be up with it over the work table and moved downwardly to at to drive the tool 16 through the workpiece 14 during the downward movement. For safety reasons, the plate 19 is electrically isolated from the rest of the boom 18.

The boom 18 and its support column 20 are preferably operated hydraulically. In Fig. 1 is a such hydraulic drive illustrated. It consists of a fixed at the lower end of the column 20, Piston 22 slidably disposed in a cylinder 24, the movement of which is controlled by a control device 26 is controlled by means of a valve body 28 displaceably mounted in the same. In the The upper position of the valve body 28 shown is in each case a lower slot 30 of the valve via the valve Cylinder 24 with an inflow line 32 for the pressure medium and an upper slot 34 of the cylinder 24 with a drain line 36 connected so that the piston 22 is driven upward. In the lower position of the valve body 28 is the reverse of the lower cylinder slot 30 with the drain line 36 and the upper cylinder slot 34 connected to the inflow line 32, so that now the piston 22 through the pressure medium is moved down. Usually the valve body 28 is by means of a spring 38 in its upper, held its rest position, so the boom 18 is lifted from the workpiece table 10. A

Electromagnet 40 ^ its armature with the valve body 28 is connected, brings the valve body in its lower position when it is excited.

For controlling the hydraulic drive to initiate a downward stroke, i.e. the working stroke of the Boom 18, a manually operable switch 42 is provided, the handle 44 on the expiring The end of the boom is arranged. In the switching position of a switch shown in Fig. 1 .S2 causes Depressing the handle 44 connects the line 46 to the AC voltage standing connecting lines 46, 48 with the intermediate line 50. But if the switch 3 * 2 its has taken another switch position, not only the handle 44 must be pressed, but also a further, provided on the side of the boom switch button 51 are operated so that to switch on Both hands of the worker over the striking plate 19 are required during an operation.

There is also a switch-on relay 52 is provided, which has three normally open contact sets 52 a, 52 b, 52 c . The contact set 52 α is connected to a holding circuit for the relay, the contact set 52 b in the excitation circuit for the electromagnet 40 and the contact set 52 c in the anode voltage supply line of an electronic control to end the working stroke. This control includes a relay 54 with two normally-closed contact sets 54α and 54 b, which are connected to the contact 52 a and 52 b of the relay 52 connected in series. Furthermore, an auxiliary relay 56 is provided with three contact sets 56 a, 56 b and 56 c, of which the normally open contact set 56 α between the winding of the relay 56 and the line 50, the normally closed contact set 56 b in the excitation circuit of the electromagnet 40 and the normally closed contact set 56 c is switched on in the excitation circuit of the relay 52. The excitation winding of the relay 56 is fed when a pressure switch 57 which is under the control of the hydraulic control device is closed or when a further switch SX is closed, when a limit switch 58 closes. If voltage is present on line 50, relay 52 is energized via contact set 56c; the contact set 52α closes and establishes a holding circuit containing the contact set 56c for the relay 52. At the same time, the contact set 52 b close, so that the electromagnet 40 is excited for switching on the working stroke, and the contact set 52 c, which thus applies anode voltage to the electronic control circuit for ending the working stroke.

The control circuit for ending the working stroke has two in a two-stage relay circuit switched thyratron tubes 60, 62 on. The electrodes of the input circuit of the thyratron tube 60 represent the control grid 64 and the cathode 66. An input circuit is connected to these two electrodes, that of a battery 68 connected in series with a resistor 70 and a grid current limiting resistor 72 exists. Battery 68 and resistor 70 together form a DC voltage source with a series resistance which essentially has only one active component. It but can also be a DC voltage source with the same internal resistance without an additional resistor be used. The two input electrodes are bridged with a smoothing capacitor 74. The DC voltage source 68 is via the lines 73 and 75 to the conductive plates 19 and 12 of the boom 18 or of the workpiece carrier 10 is connected.

The circuit shows that any conductance value connected in parallel with the DC voltage source 68 with their internal resistance, d. H. the resistor 70, a voltage divider forms the am Control grid 64 allows the DC voltage lying down, * and that the size values of the DC voltage source can be adjusted so that the thyratron tube 60 at a given size of the Shunt conductance, expediently at around ίο 500,000 ohms, ignites.

The ignition of the thyratron tube 60 causes a voltage across the cathode resistor 76 which is above a resistor 78 is connected to a circuit element with a variable time constant and in this one Switching element 80 charges with adjustable capacitive reactance, which, as shown, consists of a Step capacitor with a selector switch can exist. At the end one by the set capacity The voltage applied to the control grid 82 of the thyratron tube 62 becomes a certain delay period so big that they are in the input circuit of this tube through one together with one with it in Resistor 86 connected in series across the anode battery produced negative resistance 84 The bias voltage exceeds and thus the thyratron tube 62 can ignite.

In the output circuit of the thyratron tube 62, in addition to the DC voltage source, there is also the winding of the relay 54, which, when excited, interrupts the above-mentioned holding circuit to the intermediate line 50 by opening its upper contact set 54 a and the circuit via the electromagnet 40 by opening its lower contact set 54 b. As a result, the electromagnet 40 is no longer excited, regardless of whether the switch 42 is open or closed, so that the valve body 28 moves into its upper position and thus the working stroke of the boom 18 is ended and the latter is raised to its rest position. When the thyratron tube 62 is ignited, practically the entire anode voltage is applied to the relay 54, which is preferably selected to be substantially greater than the voltage required to attract its relay armature.

The operation of the entire device using the control circuit shown in Fig. 1 for the termination of the working stroke is as follows: The worker places a workpiece 14 on the conductive support plate 12, places a cutting or punching tool 16 on the workpiece and then depresses the handle 44 down. As a result, the relay 52 is excited, which thus closes its contacts 52 b , so that the electromagnet 40 is excited and consequently the working stroke is initiated.

During the downward and working stroke of the boom 18, the striking plate 19 hits the cutting or punching tool 16 and drives it through the workpiece 14. When the cutting edge of the tool engages the support plate 12 during the working stroke, the resistance of the line is increased 73 through the impact plate 19, the tool 16 and the support plate 12, the line path running to the line 75 is suddenly greatly reduced, and the thyratron tube 60 ignites when this resistance value falls below the value required to generate a bias on this tube, which blocks the same. Immediately when the tube is ignited, the full battery voltage B ⁺ is applied to the cathode of this thyratron tube, and the capacitive reactance switching element 80 is charged via the resistor 78. If the voltage at the switching element 80 now reaches a value,

which exceeds the bias voltage generated by the cathode resistance of the thyratron tube 62 in the input circuit of this tube, ignites the thyratron tube 62 and causes the relay 54 to be energized, which by opening its contacts 54 a the holding circuit running over the line 50 and as a result, the contacts 54 b open Excitation of the electromagnet 40 interrupts. In this time, the switch 42 is closed, remains above it, the relay 52 and thus on the closed contacts 52 c and the relay 54 energized. If, however, the switch 42 is open, the relay 52 loses its respective excitation by opening the contacts 54 a and thus the relay 54 also loses its respective excitation by opening its contacts 52 c , so that all switching elements return to the switching positions illustrated in FIG.

Fig. 2 illustrates another embodiment of the control circuit according to the invention, namely with a two-stage relay circuit, the input stage of which is that of the circuit according to FIG. 1 is similar. In this circuit, a thyratron tube 100 is provided, the control grid 102 over a resistor 106 is connected to a voltage source 104. The voltage source 104 is in the The same way as in the circuit diagram of FIG. 1 connected to the striking plate 19 'and the workpiece support plate 12. The output stage of this control circuit has two thyratron tubes 110 and 112 shown in FIG a circuit in which the current is usually drawn from the winding ends of the secondary winding 114 of a transformer 116 alternately through the thyratron tubes 110 and 112 via their common Cathode base and the winding of a relay 118 to the center tap of the secondary winding 114 flows. The thyratron tubes 110 and 112 are common permeable because their control grids 120 and 122 connect to the cathodes via grid current limiting resistors 124 and 126 and one between their common circuit node and the cathode base switched resistor 128 are connected.

The output circuit of the thyratron tube 100 runs from an anode voltage source on its connecting lead 46 'via a rectifier 130 and the contacts 132 α of a relay 132 through the tube 100 and from the cathode via a cathode resistor 134 and line 136 back to the connection line 48 'of the anode voltage source. The cathode resistor 134 is connected to one of a resistor 138 and a variable capacitor 140 existing switching element with variable time constant such switched that when the thyratron tube 100 is permeable, the one at the cathode resistor 134 is dropped Voltage across resistor 138 charges capacitor 140 and thus the top, with the control grids 120, 122 of the two thyratron tubes 110, 112 connected plate of the capacitor 140 opposite the lower plate connected to the cathode base of the two tubes is negatively charged. That Ignition of the thyratron tube 100 thus results in a dependent on the setting of the capacitor 140 Length of time the tubes 110 and 112 are blocked.

In the embodiment of the circuit according to FIG. 2, the working stroke is initiated by closing a manual switch 42 ', which in this case applies the winding of the relay 132 to the connecting lines 46' and 48 'of the anode voltage source. The relay 132 is thus excited and lets its contacts 132 α and 132 δ close; via the contacts 132a anode voltage is now applied to the anode of the Thyratronröhre 100 and through the contacts 132, the cathode of the b Thyratronröhren 110 and 112 connected to the relay 118th If the thyratron tubes 110 and 112 are working accurately, the relay 118 is now energized, thus switching the electromagnet 40 'to the voltage supply lines 46' and 48 'for energizing it and producing a holding circuit for the relay 132 that bridges the switch 42'. These latter two circuits are interrupted when an auxiliary relay 54 'is energized, which responds via a pressure switch 57' which closes when the pressure in the pressure medium system is too high.

If now when using the control circuit shown in Fig. 2, the worker in the above-described Way puts the workpiece and tool on and the switch to initiate the working stroke 42 'and then the working stroke has progressed to the point at which the resistance between the striking plate 19 'and the workpiece support ^ plate 12' is reduced to the value at which the Thyratron tube 100 ignites, the capacitor 140 charges until the control grids 120, 122 of the thyratron tubes 110,112 have a sufficient negative voltage compared to their cathodes and thus a these tubes is blocked. At the same time, the inductance of the winding of the relay 118 by the others, namely that of the two tubes 110, 112, which was the last to be permeable, continued to flow current. During the next half of the cycle, the uninterrupted discharge of this tube acts on the one half of the secondary winding 114 opposite voltage, so that the voltage across the winding of the Relay 118 voltage rises to maintain the discharge, above its normal male operating voltage. To take advantage of the energy stored in the winding of the relay 118 To dismantle quickly, two discharge tubes 142 and 144 are provided in parallel with this relay winding. These tubes are dimensioned so that their ignition voltage is slightly above the normal operating voltage of relay 118 is located. If, under the circumstances just discussed, the output circuit is interrupted , these discharge tubes ignite immediately and build up the energy for the winding of the relay 118 off, so that it falls off and its contacts open, consequently the electromagnet 40 'loses its excitation and thus the working stroke of the boom 18' ends will.

As shown in Fig. 1, the handle 44 is through its attachment to the boom 18 with the machine frame and thus via the line 75 with the workpiece support plate 12 connected; the line 75 practically does not need to be provided, since this connection already takes place via the machine frame itself.

Should the impact plate 19, while the boom executes its working stroke and the worker with one hand grasps the handle 44 on the other hand or one of its fingers, who got into the movement path of the boom by chance, is the worker's body on the one hand Input circuit of the thyratron tube 60 is parallel electrical resistance. If then the Resistance 70 a sufficiently large proportion of the total resistance of the resistance 70 and body resistance of the worker's existing voltage divider network, the grid bias decreases to the value of the ignition voltage of the tube. The value of the resistor 70 used must be low enough under normal working conditions to stop the working stroke before it is completely through

to avoid cutting or punching the workpiece. Apart from the very rare working conditions that exist when materials with a low ohmic resistance are cut or punched, the limit value of the input resistance given by the aforementioned requirement can be selected to be sufficiently large so that in the event that the worker can hold the handle with one hand 44 and is touched by the striking plate 19 with the other hand, the resistance between the handle and the striking plate (and thus the resistance between the boom 18 and the workpiece table 10) is below the limit value even under the most unfavorable contact conditions relating to the touch of the worker's hand on the handle 44 lies. As a limit value for the input resistance, around 680,000 ohms are sufficient for normal cutting or punching of upper leather.

The time taken up by one working stroke of the machine, about 1 second, is so short that in the vast majority of cases the worker will not have released his hand from the handle 44 during the downward movement of the boom. Should the striking plate 19 come into contact with any part of the worker's body during the working stroke, the thyratron tube 62 will ignite and the working stroke will end within a fraction of a second. This fraction is determined by the respective setting of the selector switch of the switching element 80 and depends on the respective working conditions.

Claims (1)

Patent claims: 1. Automatic electrical control circuit for pressing, punching or the like. That with an electrical conductive workpiece carrier, e.g. a workpiece table, a pressed part, e.g. B. a cantilever arm, which can be moved vertically with respect to the workpiece carrier around a tool such as a punch to be driven by a workpiece placed on the workpiece carrier, and a drive for actuation of said pressing part are provided, so that this drive contains a control which end the movement of the pressed part towards the workpiece carrier and raise the pressed part again can, characterized in that the control circuit has a switch-off relay circuit a DC input stage containing a grid controlled gas discharge tube (60), which in the normal state of a DC voltage source with one lying in series with it Resistance, which has essentially only one active component, receives a bias at which blocks them, and that this DC voltage source on the one hand to the input electrodes of this Tube and on the other hand to the electrically conductive organs of the workpiece carrier and the pressed part is connected in parallel, so that the resistance between these organs with the series resistance the DC voltage source forms a voltage distributor and thereby achieved that the effective grid bias of the tube the resistance between the press part and the workpiece carrier is always proportional and when it is reduced below a predetermined ι Resistance value is brought to the voltage limit value g <at which the tube ignites and then: becomes conductive. 2. Control circuit according to claim 1, dadurc characterized in that in the output circuit de said tube (60) a circuit is connected with a time constant that can be changed by appropriate setting, so that the output voltage of this circuit and consequently! whose delay effect consequently Trenf ¹ voltage from the DC power input stage of Ände conclusions of the resistance between the stirring organs be independent. 3. Control circuit according to claim 1, characterized in that a plurality of gas discharge tube ^ are switched into a two-stage control circuit and that this circuit einj Switching j connected between the two stages member with changeable time constant and an in! switched the output circuit of the second stage! Has relay. ί 4. Control circuit according to claim 1, marked-i is characterized by the design as a two-stage, for the end of the working stroke provided control circuit with a usually conductive alternating current output stage, which when a Ent- ^ charge of a tube lying in the input circuit interrupts its current, so that after a a predetermined period of time after the onset of this discharge, the actuation of a relay; to be led. 5. Control circuit according to claim 4, characterized in that discharge tubes (142, 144) are connected via the coil in the relay of the AC output stage and when this stage is switched off, conduct in order to accelerate the opening of the relay. 6. Control circuit according to claim 1, characterized in that an electrically conductive handle (44), which is operated by one hand of the worker to switch on the drive of the pressed part, electrically connected to the workpiece carrier (12) and therefore to the control circuit is, so that when the pressed part hits any part of the other hand of the Worker established a circuit between the workpiece carrier and the pressed part and the Input voltage of the control circuit is changed so that the downward movement of the Pressing stops immediately. Publications considered: Workshop technology and mechanical engineering, August 1954, P. 369/370;
VDI magazine from November 1, 1954, p. 1061 / 1062. 1 sheet of drawings ® 809 560/354 7.58