US2994010A - Device for the firing of the electric discharge tube - Google Patents

Description

July 25, 1961 MONFRAY 2,994,010

DEVICE FOR THE FIRING OF THE ELECTRIC DISCHARGE TUBE Filed March 30, 1959 2 Sheets-Sheet 1 M/pm,

J ly 19 1 B. MONFRAY 2,994,010

DEVICE FOR THE FIRING OF THE ELECTRIC DISCHARGE TUBE Filed March 30, 1959 2 Sheets-Sheet 2 Pie-4 /n n cmor Q BEND/7' MONFRAY b wm m Affornep United States Patent 2,994,010 DEVICE FOR THE FIRING OF THE ELECTRIC DISCHARGE TUBE Benoit Monfray, Belleville-sur-Saone, France, assignor to Societe Anonyme de Bobinage pour IIndustrie et la Radio, Belleville-sur-Saone, France, a corporation of France Filed Mar. 30, 1959, Ser. No. 802,755 Claims priority, application France Apr. 4, 1958 12 Claims. (Cl. 315-100) The present invention relates to a device for the firing of electric discharge tubes.

Devices of this type are already known which include a relay contact mounted across the tube so as to allow the preheating current to pass in its electrodes, and the opening of said contact to bring about the firing is actuated by the lengthening of a resistance wire, electrically heated.

In some of the known devices of this type, the movable element in the contact tends, under action of a spring, to be separated from the stationary element, but it is maintained in contacting position by a rigid connexion with the resistance wire, acting in the opposite way, at least until the lengthening of said wire allows the motion of the movable element and thereby the opening of the circuit.

These known devices require accordingly a rather complicated and relatively bulky mechanism: the working lacks in safety and the cost price is high.

In other known devices of the same type, a lever, actuated by a spring, is held back by the resistance wire, at least until the lengthening of said Wire allows the rocking of the lever which then can move the movable element of the contact apart from the stationary element.

These last devices show, accordingly, and to an increased degree, the same drawbacks as the first mentioned devices.

The device according to the invention belongs to the same type and uses a resistance wire like the devices above described, but it offers none of their drawbacks: it is characterized by either one of the following features and preferably by their combination:

(1) The movable element in the contact is supported by a flat spring which is kept stretched by the resistance wire to normally secure the closing of said contact whereas the lengthening of this wire brings about the opening.

(2) The heater voltage of the resistance wire is supplied by the secondaryof a transformer, the primary of which is connected in series with the tube, and which includes a third winding connected in such a way that the firing current generates a magnetic flux opposed to the flux generated by said primary, so that the resulting flux will generate in the secondary a heating current which is about the same in normal working as during the firing.

According to a preferred form of embodiment, the resistance Wire is connected with the free end of the fiat spring which supports the movable element of the contact and normally exerts a traction on it, preferably in a parallel direction, thereby elastically incurvating said spring towards the stationary element of the contact; moreover, this stationary element is supported by a second flat spring, both springs, and also a cable eye to fix the resistance wire, being clamped in a pile of insulating spacers.

The starter thus designated, which differs from a onecontact relay of the rest type only by the addition of a resistance wire tightened between the free end of one of the springs and a cable eye incorporated in the pile, offers a reduced 'bulkiness and a noteworthy mechanical Patented July 25, 1961 simplicity which bring about a very low cost price and a perfect working safety.

By way of example, several forms of embodiment of the firing device according to the invention are described hereafter and schematically illustrated in the annexed drawing:

FIGURE 1 shows in elevation the pile formed by the flat springs and the resistance wire, constituting the starter proper.

FIGURES 2 and 3 are two different connection diagrams of an electric discharge tube, the firing circuit of which includes a starter similar to the starter of FIG- URE 1.

FIGURE 4 illustrates an alternate embodiment of the starter of FIGURE 1.

The starter illustrated in FIGURE 1 is essentially constituted by two flat springs 1, 2, and a bimetallic strip 3, arranged in parallel and interconnected at one end, with interposition of insulating spacers 4, by any suitable clamping device 5, such as a rivet, screw, nut, etc.

The free ends of the blades 1, 2, 3 bear contact elements 1', 2, 3', inserted for instance in the blades, the contact element of the intermediate blade 2 being a double contact to cooperate with both 1 and 3'.

The bimetallic strip 3 is disposed in relation to spring 2 so that the contact elements 2', 3, come into contact with each other when the two blades 2, 3, are at a same temperature. The plate spring 1 is disposed, in relation to plate spring 2, so that the contacts 1', 2', are not normally in contact with each other.

A wire 6 is stretched between a point at the free end of the flat spring 1this end may be, for instance, chocked below the contact element 1' inserted in flat spring 1 and a cable eye 7 incorporated in the pile between springs 1 and 2, from which said cable eye is separated by insulating spacers 4.

The tension of this wire is selected so that it normally will exert upon the free end of plate spring 1 a pull about parallel to said plate spring, thereby elastically incurving it so that the contact element 1 comes in contact with the contact element 2, as shown in FIGURE 1.

The wire 6 is to be conductive with a noteworthy electrical resistance for a comparatively short length and a rather important thermic expansion coefficient: therefore, a metallic wire having a rather high resistivity is selected.

A small heating resistance 8, wire-wound for instance, is placed against the bimetallic strip 3: its ends are collected, the one with the strip-by a welding for instance-and the other with an insulated conductor 9, provided with a terminal 10 incorporated in the pile below the bimetallic strip 3 and insulated by spacers 4.

The blades 1, 3 and contacts 7, 10, are provided with suitable means-not shown-to connect conducting wires.

In the diagram of FIGURE 2, the electrodes 12, 12 of the electric discharge tube 11 are both connected at one end, through a conductor, with a pole of the supply source 13, the electrode 12' directly and the electrode 12 through the winding of a self-inductance 14: the other ends of electrodes 12, 12', are connected by conductors, respectively with the plate spring 1 and the terminal 210 of the starter.

On the pole core of the self-inductance 14 is wound a second Winding 14, the ends of which are connected through conductors, the one with the spring 1, the other with the contact 7 of the starter.

A condenser 15 is connected between blades 1 and 3 of the starter.

When the voltage existing between the poles of the supply source 13 is, at the closing of the switch 16, applied on the tube 11 in series with the self-inductance 14, the contact 12 and 2''3' being closed, the current flows through the closed circuit 131614-12- 3 1-1'2'3'389-101216-13; the current heats progressively the electrodes 12, 12'. Simultaneously, the main winding 14 of the self-inductance inducesin thesecondary winding 14 a voltage which circulates a current in the closed circuit 147-6'1'- 114', progressively heating the resistance wire 6.

When the lengthening of this wire is sufiicient to allow, on account of the decrease of the pull exerted upon the free end of the incurved plate spring 1, the straightening at least partly-of said spring 1, the contact between contacts 1', 2, is interrupted and the heating circuit of the electrodes 12, 12' is cut olf. As the self-inductance 14 is connected to this circuit, a high overvoltage surges at the same time in said electrodes and causes the starting of a permanent electric discharge in the gas filling up the tube 1: the firing is made easier by the condenser 15 connected in parallel with the cut-otf contact 12.

Of course, the characteristics of the wire '6 and its heating voltage are selected so that the current heating the electrodes is only cut off when these electrodes have reached their optimum emission temperature, below which they could risk to be damaged by a wrenching of material.

On the other hand, it is desirable that the pull on the wire 6 is sufficiently strong to deform the end of the plate spring 1 to such an extent that it deforms also slightly the end of spring 2: when the expansion reduces the tension of the wire 6, the two contacts keeping in contact move first together until the plate spring 1 has resumed its original shape and then the cut-off takes place. This follow on phenomenon is well known in the technique of relays and offers, in this case, the same advantages as it-allows, in particular, to suppress the working failures which could result from manufacture margins.

When the tube is tired, its discharge current passing through the winding 14 of the self-inductance 14 induces in the winding 14' a current keeping the wire 6 at a temperature high enough to keep open the contact- When the switch 16 is opened, the discharge stops and-also the current heating the wire 6. As it cools down progressively, thewire 6 comes back to its original length and pulls upon the free end of the plate spring 1 to bring its contact element 1 into contact with the contact element 2': the starter is ready for a new firing.

If, for any reason, the opening of the contact 12 does not take place, the heating current of the electrodes 12, 12', heating also the resistance 8, will bring about about-the deformation of the bimetallic strip 32' the contact element 3 ceases to 'be in contact with the contact element 2 and brings about the cut-oif of the heating current of said electrodes and the firing of the tube 11,-as it has been previously described.

The time constantsfor the heating of the resistance wire .6 and the bimetallic strip 3 are evidently chosen sothat the deformation of the strip 3 can interfere after the normal expansion of the wire, said bimetallic strip being only an emergency device.

Of .course, the starter of FIGURE 1 can be placed in a small casing, with four electric connections only coming out of it.

The connection diagram of FIGURE 3 differs of the diagram of FIGURE 2 only in that the self-inductance 14 is not provided with an auxiliary winding, and that the heating of the wire 6 is secured by the secondary 17." of a transformer 17, the primary 17' of which is connected in series with the self-inductance 14 and the tube 11. This transformer includes a third winding 17", connected in series between the electrode 12 and the plate spring 1 of the starter, with such a polarity that, during the firing, the heating current of the electrodes generates, by passing through the windings 17' and 17", opposing magnetic fluxes, the resultant of which induces in the winding 17" the current intended to heat the resistancewire 6.

This assembly operates exactly like the assembly of FIGURE 2 except that, when the discharge in the tube is started, the heating circuit of its electrodes being cut, no current passes through the winding 17"; the heating of the wire 6 is then exclusively induced by the are current passing through the winding 17'; as this arc current is much smaller than the current passing through 17 and 17 during the firing, it is possible to choose the characteristics of the transformer 17 so that the heating voltage of the wire 6, induced in the winding 17" by the resultant flux of the windings 1'7 and 17"., is about the sameat the discharge ratewhen the first winding only is passed through by the current and during the firing period when both windings are passed through.

Thanks to this arrangement, the temperature in operation of the resistance wire is always about the same and also its lengthening.

Of course, the working safety and the life duration of the apparatus are greatly improved.

Without departing from the frame of the present invention, it is possible to obtain the same working and life duration improvements when using starters provided with a resistance wire of any type, by carrying out the heating of this wire by means of a magnetic counterreaction transformer such as above described.

The form of embodiment illustrated in FIGURE 4 diifers from the starter of FIGURE 1 in the following features:

On the one hand, the plate spring 1 passes through a rectangular slot or window 18 in the folded down end of a rigid blade 18, the other end of which is clamped in the pile just above said plate spring 1.

On the other hand, the bimetallic strip 3, instead of being rectilinear and provided at its end with a contact intended to cooperate with the contact 2' of plate spring 2, is folded up at its free end 3 towards said spring 2: in addition, a rigid blade 19 shorter than the spring 2 is placed just above said spring in the pile. To end, the spring plate 2 is curved so that its free endnor-rnally tends to deviate from the rigid blade 19 with theresult that its free end, which beyond the blade 19 is twice bent to bring the contact elements 2 near the free end of the spring 1, tends also to move apart from this spring 1 and of its contact element 1': nevertheless, the arrangement is such that, when the bimetallic strip 3 is at ambient temperature, its curved end 3' pushes the free part of the spring 2 against the rigid blade 19, acting as a stop (as shown in FIGURE 4); if the resistance wire 6 is also at ambient temperature, it keeps the spring .1 in the illustrated position, the contact element 1' being into contact with the contact element 2' of the spring 2.

This starter, as above described, may be immediately incorporated in the firing circuits for electric discharge tubes illustrated in FIGURES 2, 3, instead of the starter illustrated in FIGURE 1, the homologous cable eyes having in both cases the same reference marks. The condenser 15, illustrated in these figures, intended to facilitate thefiring of the tubeat the opening of the contact 1-2', can then be connected with the cable eye 7 on the one hand and, on the other hand, either with the bimetallic strip 3 or the terminal 10, at will.

The working of this starter, when incorporatedin one of the firing circuits illustrated in FIGURES 2, 3, is very similar to the working of the starter of FIGURE 1:.particularly, the normal working is the same in both cases, the heating of the resistance wire 6 produced by the current passing through this wire as soon as a voltage is applied on the electrodes of the tube, brings about a thermal lengthening of said wire 6, which, after a given time, is suificient to allow the spring 1 to move apart,

its free end from the free end of the spring ,2, ,the two contact elements 1, 2', being no longer in contact:- the result is that the preheatingcurrent of the electrodes of the tube passing through their contact point is cutpif: and the electric discharge in the tube is started, as ,it,

has been previously explained. 'The upper and lower edges of the window 18' in the rigid blade 18 through which passes the spring 1 act as stops to limit the movements of this plate spring 1 resulting from the length variations of the resistance wire 6.

In the case of the starter of FIGURE 4, if, for any reason, the opening of the contact 1- does not take place normally as above indicated, since the preheating current of the electrodes passes also through the resistance 8 as long as the contact 1-2' is not cut off, the bimetallic strip 3 is progressively deformed by the heat given out by this resistance 8 and its incurved end 3' pushes no longer the plate spring 2 against the blade .19: the spring 2, on account of its bend, tends to move its free end apart from the free end of spring 1, the contact between .1 and 2' is interrupted and the current for the preheating of the electrodes is cut off, bringing about the firing of the tube.

Like for the starter illustrated in FIGURE 1, the time constants related to the heating of the resistance wire 6 and of the bimetallic strip 3 are evidently chosen so that the deformation of the bimetallic strip can only take place after the normal lengthening of the spring 1, the bimetallic strip acting only as a safety device.

What is claimed is:

1. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a selfinductance and a switch connected between the electrodes of said discharge tube and the poles of said source of supply voltage, and a starting device, including two contact pieces, one of which is stationary and electrically connected with one of the electrodes of the tube, a plate spring, one end of which is stationary and the other is free and supports the other of said contact pieces, said plate spring being electrically connected with the other electrode of the tube and so disposed that its supported contact piece is not normally in contact with the other stationary contact piece, a resistance metallic wire stretched between a stationary point and the free end of said plate spring, so as to deform this end and to bring its supported contact piece into contact with the stationary contact piece when said resistance wire is at the ambient temperature, whereby when said switch is closed and the supply voltage is applied upon the electrodes of the tube, a preheating current passes through said electrodes and the contact pieces, and means to energize said resistance wire with an electric heating current as long as said switch is closed and supply voltage is applied on the tube, whereby, in consequence of the thermal expansion of said resistance wire, the plate spring contact piece is moved apart from the stationary contact piece, and thereby the preheating current of the electrodes is cut off when they have reached their normal working temperature.

2. A system according to claim 1, in which the'rcsistance wire is disposed so as to exert on the free end of the plate spring a pull substantially parallel to said spring, thereby elastically incurvating said free end towards the other contact piece.

3. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a self-inductance and a switch connected between the elec trodes of said discharge tube and the poles of said sources of supply voltage, and a starting device, including two contact pieces, one of which is stationary and electrically connected with one of the electrodes of the tube, a plate spring, one end of which is stationary and the other is free and supports the other of said contact pieces, said plate being electrically connected with the other electrode of the tube and so disposed that its supported contact piece is not normally in contact with the stationary contact piece, a resistance metallic wire stretched between a stationary point and the free end of said plate spring, so as to deform this end and to bring its supported contact piece into contact with the stationary contact piece when said resistance wire is at the ambient temperature, whereby when said switch is closed and the supply voltage is applied upon the electrodes of the tube, a preheating current passes through said electrodes and the contact pieces, means to energize said resistance wire with an electric heating current, as long as said switch is closed and the supply voltage is applied on the tube, whereby, in consequence of the thermal expansion of said resistance wire, the plate spring contact piece is moved apart from the other stationary contact piece and thereby the preheating current of the electrodes is cut off when they have reached their normal working temperature, a further contact piece normally in contact with said stationary contact piece, and means to move said further contact piece apart from said stationary contact piece under action of the heat supplied by the preheating current of the electrodes, with a time delay longer than the thermal expansion time of said resistance wire, so as to cut off said preheating current in case the resistance wire expansion has not already brought about this cut ofi.

4. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a self-inductance and a switch connected between the electrodes of said discharge tube and the poles of said source of supply voltage, and a starting device, including a first and a second plate spring, the first of which at least is electrically connected with one of the two electrodes of the tube, said plate springs having each one end clamped in a pile of insulating spacers, so as to be disposed about parallel to each other, while their free ends support two contact pieces facing each other, but normally not in contact with each other, a metallic resistance wire stretched between a lug clamped in said pile of insulated spacers and the free end of said first plate spring, so as to bend said first plate spring and bring its contact piece into contact with the contact piece of said second plate spring when said resistance wire is at the ambient temperature, whereby, when said switch is closed and the supply voltage is applied upon the electrodes of the tube, a preheating current passes through said electrodes and the contact pieces, means to energize said resistance wire with an electric heating current as long as said switch is closed and the supply voltage is applied on the tube, whereby, in consequence of the thermal expansion of said resistance wire, the contact piece of said first plate spring is moved apart from the contact piece of said second plate spring and thereby the preheating current of the electrodes is cut off when they have reached their normal working temperature, a bimetallic strip, one end of which is clamped in the pile of insulating spacers so that it is about par allel to said plate springs, while its free end supports a further contact piece which, when said bimetallic strip is at the ambient temperature, is normally in contact with the contact piece of said second plate spring, and an electric resistance, electrically connected between said bimetallic strip and the other tube electrode, said resistance being disposed against the bimetallic strip so that the heat generated by the preheating current of the electrodes, when passing through said resistance, heats up said bimetallic strip and brings about its distortion, whereby the contact piece of said bimetallic strip is moved apart from the contact piece of said second plate spring, and said preheating current is cut oflf, the heating time of the bimetallic strip being longer than the thermal expansion time of the resistance wire.

5. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a self-inductance and a switch connected between the electrodes of said discharge tube and the poles of said source of supply voltage, and a starting device, including a first and a second plate spring, the first of which at least is electrically connected with one of the two electrodes of the tube, said plate springs having each one end clamped in a pile of insulating spacers, so as to be disposed about parallel to each other, while their free ends support two contact pieces facing each other, but normally not in contact with each other, a metallic resistance wire stretched between a lug clamped in said pile of insulated spacers and the free end of said first plate spring, so as to bend said first plate spring and to pull its contact piece towards the contact piece of said second plate spring, a bimetallic strip, one end of which is clamped in the pile of insulating spacers, said bimetallic strip being arranged so as to push the free end of said second plate spring towards the free end of said first plate spring, whereby the contact pieces of the two plate springs are in contact with each other when said resistance wire and said bimetallic strip are both at the ambient temperature, so that, when said switch is closed and the supply voltage is applied upon the electrodes of the tube, a preheating cur rent passes through said electrodes and the contact pieces, means to energize said resistance wire with an electric heating current as long as said switch is closed and the supply voltage is applied on the tube, whereby, in consequence of the thermal expansion of said resistance wire, the contact piece of said first plate spring is moved apart from the contact piece of said second plate spring, and thereby the preheating current of the electrodes is cut oif when they have reached their normal working temperature, and an electric resistance, electrically connected between said bimetallic strip and the other tube electrode, said resistance being disposed against the bimetallic strip so that the heat generated by the preheating current of the electrodes, when passing through said resistance, heats up said bimetallic strip and brings about its distortion, whereby said bimetallic strip stops pushing thefree end of said second plate spring, the contact piece of which is thereby moved apart from the contact piece of said first plate spring, thereby cutting oil the preheating current, the heating time of the bimetallic strip being longer than the thermal expansion time of the resistance wire.

6. A system according to claim 5, in which, when the bimetallic strip is at the ambient temperature, its free end pushes the free end of the second plate spring towards a rigid blade disposed in the pile of insulating spacers between said plate springs, and acting as a stop.

7. A system according to claim 5, in which the free end of the bimetallic strip is curved towards the second plate spring.

'8. A system according to claim 6, in which the free end of'the second plate spring, which is pushed by the bimetallic strip, is bent, beyond the free end of the rigid blade acting as a stop, towards the free end of the first plate spring.

9. Device according to claim 6, in which stationary stops limit the displacements of the first plate spring.

10. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a switch, connected between the electrodes of said discharge tube and the poles of said source of supp-1y voltage, and a starting device, including a first and a second plate spring, the first of which at least is electrically connected with one of the two electrodes of the tube, said plate springs having each one end clamped in a pile of insulating spacers, so as to be disposed about parallel to each other, while their free ends support two contact pieces facing each other, but normally not in contact with each other, a metallic resistance wire stretched, between a lug clamped in said pile of insulated spacers and the free end of said first plate spring, so as to bend said first plate spring and bring its contact piece into contact with the contact piece of said second plate spring when said resistance wire is at the ambient temperature, whereby, when said switch is closed and the supply voltage is applied upon the electrodes of the tube, a preheating current passes through said electrodes and the contact pieces, a transformer, the primary winding of which is inserted between one pole of said source of supply voltage and one of the electrodes of the tube, whereby said primary winding is passed through, before the firing of the tube, by the preheating current of its electrodes and, after the firing of the tube, by its discharge current, the selfinductance of said primary winding promoting the start of this discharge and securing afterwards its steadiness, whereas the secondary winding of said transformer is connected so as to energize said resistance wire with an electric heating current as long as said switch is closed and the supply voltage is applied on the tube, whereby, in consequence of the thermal expansion of said resistance wire, the contact piece of said first plate spring is moved apart from the contact piece of said second plate spring and thereby the preheating current of the electrodes is cut off when they have reached their normal working temperature.

11. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, each of said electrodes being electrically connected to one pole of said source of supply voltage, a self-inductance and a switch connected between the electrodes of said discharge tube and the poles of said source of supply voltage, and a starting device, including two contact pieces which are each electrically connected with one of the electrodes of the tube, and disposed so as normally to be in contact with each other, whereby a preheating current passes through said contact pieces and electrodes when said switch is closed, a stretched resistance wire, a transformer, the primary winding of which is inserted between one pole of said source of supply voltage and the electrode of the tube which is connected to said last pole, the secondary winding of said transformer being connected with the ends of said resistance wire, mechanical means to transform the thermal lengthening of said resistance wire due to the heating electric current generated therein by the secondary winding of said tnansformer when said switch is closed, into an opening movement of said contact pieces, whereby the electrode preheating current is cut off and the discharge starts to fire, and to transform the shortening of said resistance wire, when said switch is opened, into a closing movement of said contact pieces, said transformer including in addition a second primary winding inserted between one of the electrodes of the tube and the contact iece which is connected to said last electrode, so that said second primary winding is passed through only by the preheating current of the electrodes before the starting of the electric discharge, the winding senses of the two primary windings of the transformer being such that said preheating current generates, in passing in series through said primary windings, opposing fluxes through the single secondary winding, whereby this secondary winding generates in said resistance wire fairly equal heating currents before and after the starting of the electrode discharge.

12. A system comprising in combination, a source of supply voltage having two poles, an electric discharge tube having two electrodes constructed to receive a preheating current, cach of said electrodes being electrically connected to one pole of said source of supply voltage, a self-inductance and a switch connected between the electrodes of said discharge tube and the poles of said source of supply voltage, and a starting device, including two contact pieces, which are each electrically connected with one of the electrodes of the tube, and disposed so as normally to be in closed relation with each other, where by a preheating current passes through said contact pieces and electrodes when said switch is closed, a stretched resistance wire, means to energize said resistance wire with an electric heating current as long as said switch is closed and the supply voltage is applied on the tube, mechanical means to transform the thermal lengthening 10 of said heated resistance wire into an opening movement of said contact pieces, whereby the electrodes preheating current is cut oif and the discharge starts to fire, and to transform the shortening of said resistance wire, when said switch is opened, into a closing movement of said contact pieces.

References Cited in the file of this patent UNITED STATES PATENTS Hehenkarnp Mar. 30, 1948 2,667,604 Hamilton Jan. 26, 1954

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