US3513281A - Switching arrangement and device for the automatic lifting of arc plasma torches - Google Patents

Description

May 19, 1970 L. HAASE ETAL SWITCHING ARRANGEMENT AND DEVICE FOR THE AUTOMATIC LIFTING OF ARC PLASMA TORCHES Filed Aug. 15, 1966 FIG. I.

FIG. 2.

5 m REE SH MAC AO V NRC: I HO TD U LR ATTORNEY US. Cl. 21969 2 Claims ABSTRACT OF THE DISCLOSURE A circuit arrangement and apparatus for automatic lifting ofarc plasma torches, in particular for cutting, which comprises a switching member disposed in the arc circuit, An adjustable time lag member is electronically or electromechanically controlled by the switching mem her during. the flow of current of a main arc and thereby limiting timely the lifting of the arc burner head.

The present invention relates to a switching arrangement and va device for the automaticlifting of arc plasma torches, especially for cutting into works with great thick= ness.

It is known that on cutting in without cut-in hole the metal, fused until the work piece is cut through, is thrown upwardlyi vand, in particular with work pieces of great thickness, owing to the low rate of feed, forms electrically conductive connections, which capse short circuits be= tween the nozzle of the plasma torch and the work piece, whereby the nozzle is heavily damaged or totally destroyed.

It is further known that the plasma burner can be lifted by hand on ignition of the electric arc, until the plasma flame has cut through the work, Ignition from a corre spondingly great distance is not possible. In most cases the torch, because of the delayed reaction of the operator, is lifted too late, so that the nozzle of the plasma torch is affected despite this lifting action. Furthermore, there is the drawback that manual lifting is very difficult or even quite impossible, when using the plasma torch in cutting machines, especially machines with several torches,

It is, therefore, one object of the present invention to provide a" device for the automatic'lifting of arc plasma torches which protects the nozzle of the plasma torch in the cuttirig-in operation above the work piece from dam ages or even destruction.

It is another object of the present invention to provide a device for the automatic lifting of arc plasma torches, which includes an automatic lifting device, which avoids the disadyantages described and substantial y increases the durability'gof the service life,

It is yetanother object of the present invention,, to pro vide a device for the automatic jlifting of arc plasma torches wherein a current relay, ipcluded in the circuit of the main arc, is used as a controlinernber for the lifting operation of the plasma torch suchjthat at the moment of ignition vof the main arc and by the current increase, thereby caused, the current relay isienergized and closes its make contact. Through the current relay by means of its make contact, an adjustable time lag relay with a rest contact is switched on, which opens on elapse of the set time lag and ends the lifting operations.

It is also an object of the present invention to provide a, connection system and device for the automatic lifting of arc plasma torches, wherein by means of the make con tact of the current relay and by means of the rest contact of the time lag relay, the drive of the lifting device is controlled,

3,5132% Fatented May 19, 1979 It is a further object of the present invention to provide a connection system and device for the automatic lifting of arc plasma torches, wherein the device for lifting the plasma torch is fixed on a generally known device for vertical adjustment, such as a dovetail guide, which comprises an adjustable stop, a rack, a gear wheel, a gear shaft, a lever with slot, and an electromagnet, by the armature of which the device is driven.

The technical and economical advantages, especially the technical progress represented by the present invention resides in the fact, that when cutting into a work piece with great thickness, the nozzle of the plasma torch is no longer damaged, and reliable cutting-in is ensured even when using plasma torches on cutting machines,

Wit these and other objects in. view which will become apparent in the following detailed description, the present invention will he clearly understood in connection with the accompanying drawings, in which:

FIG, 1 is a diagram disclosing a connection system for lifting a plasma torch in a cutting-in operation above the work piece; and

FIG, 2 is an. elevation of a device for lifting a plasma torch,

Referring now to the drawing, the plasma torch I, is fixed on a generally known dovetail guide 2, which in eludes an adjustable abutment 3, The plasma torch 1' can be lifted by means of a gear rack 4 and a gear wheel 5 upon rotation of a gear shaft 6, On the gear shaft 6, a lever 7 is rotatably arranged, which can be locked. in any position, for adjustment of the required lifting height, by a set screw 8, An armature 10 of an. electromagnet 11 is operatively connected with a slot 9 of the lever 7, so that upon energizing the electromagnet. 11, the plasma torch 1 is lifted, Upon. deenergizing the electromagnet 11, the plasma torch 1 is returned to its lower position by a spring force (not shown), The electrical circuit for actua= tion of the electromagnet 11 comprises a suitable power source 1'" and an electronic or electromagneticcontrol the vice 14 which is normally not set for passing and a time retarding relay 15., Upon excitement of the electronic electromagnetic control device 14, the pole 13 is disposed above the control device 1d at the point 22 of: the alter hating electric source,

The electronic or electromagnetic device 14 is already incorporated in most of the plasma cutting plants and is energized by the current of the. main are, The time lag relay 15 attracts with delay and is switched on. by the make contact 12 of the electronic or electromechaniccom trol device 14, The time lag is preferably adjustable, in order to ensure adaptation of the switch=on moment the electromagnet 11 to the time passing between ignition of the main arm and. cutting through of the work piece 16 and. should be adjusted in accordance with. empirical values,

Upon ignition of the main arc of the plasma torch "a, the control device 14 attracts and by means of its make contact 12 switches on a rectifier 17 and, thereby, the eleo trornagnet. 11, as well the time lag relay 15, The electro= magnetl l turns by means of the armature 10, the lever 7 and the gear shaft 6, and thereby the gear wheel 5, and the latter moves the rack 4 guiding by means of the dovetail guide 2 the plasma torch. l, The lifting motion limited by the stroke of armature 10, Shortly after we plasma flame has cut through the work piece 16, the time lag relay 15 should have run out, whereby its contact 13 is opened and the electromagnet 1,1 is switched off, The running time of the time relay 15 can he in= creased, so that a predeterminedcutting length can be obtained, The armature 10 of the electromagnet 11 is dropped and the plasma torch 1 returns to its lower posttion, which is determined by the stop 3,

Upon switching off of the main arc, control device drops, whereby also the time iag relay 15 droppedt Now the device and the circuit arrangement are ready for another cutting in operation When using the connection system, according to the present invention, on cutting machines comprising a lift ing device preferably of the circuit of the present inven= tion, only its indicated control lines 18 and 19 should he preferably connected with this device:

Not required in this case are the electromagnet 11 and the rectifier 17, as well as the device shown in FIGC 2t Moreover, the time lag relay 15 and its rest contact 13 can be dispensed with, if a cutting machine is already equipped with a time lag member, that can he used for this purpose, so that only the control lines 19 and. 20, or if even the power source is not required, the control lines 20 and 21 are connected with the cutting machine,

While We have disclosed one embodiment of the pres ent invention, it is to be understood that this embodiment is given by example only and not in a limiting sense, the scopeof the present invention. being determined by the objects and the claims We claim:

It, A circuit arrangement and apparatus for automatic lifting of are plasma torches, in particular for cutting, comprising mechanical means for first moving a plasma torch to a position for initially cutting through a workpiece, circuit means including adjustable time lag means op eratively connected, to and for activating said rne= chanical means to first move said torch to said first {it position and for terminating said first moving of said torch after expiration of a time lag period correspond ing to the cutting through of said workpiece, and thereafter permitting a second movement of said torch in a direction opposite to said first moving, and

means for causing said second movement of said torch to a second position. thereby completing a cutting operation cycle of said workpiece 2 The apparatus, as set forth in claim it, which includes a dove-tail guide means, a plasma torch secured to said dove-tail guide means, and

said dove-tail guide means comprising an adjustable abutment member, a gear rack, a gear meshing with said gear rack, a lever having a longitudinal slot and an electromagnet including an armature and tap eratively connected with said armature for driving said apparatus, said electro'magnet including said armature constituting a part of said circuit means.

References Cited ANTHONY BARTIS, Primary Examiner 3f GO SMITH, Assistant Examiner U5, Ci,

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