US1005222A - Electrodynamic-brake control. - Google Patents

Description

J. .11. IHLDER. ELEGTBODYNAMIG BRAKE CONTROL.

APPLICATION FILED MAR. 13, 1908.

1,005,222. Patented 001;. 10, 1911.

2 SHEETSSHEET 1.

' J. D. IHLDER.

Patented Oct. 10,1911.

2 SHEETS-SHEET 2.

UNITED, s rArns PATENT OFFICE.

JOHN D. IHLDER, OF NEW YORK, N. ASSIGNOR TO OTIS ELEVATOR COMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF .NEW JERSEY.

ELECTRODYNAMIO-BRAKE CONTROL.

Paanad'oa. 10,1911.

Application filed March 13, 1908. Serial No. 420,811.

To all whom it may concern.-

Be it known that 1, JOHN D. IBLDER, a

citizen of the United States, residing in New.

York, in the county of New York and State of New York, have invented a new and useful Improvement in Electrodynamic-Brake Control, of which the following is aspeoification.

My invention relates. to means for controlling the operation of an electro-dynamic brake.

In my co-pending-a lication filed October 11, 1905, Serial 0. 282,330, I have shown and described an electro-dyna'mic brake connected to run with an electric motor and adapted to be brought into operation to retard or apply a braking action to the motor.

The present invention comprises improvements in or additions to such brake mechanism, and consists more particularly of means for controlling the operation of such brake.

One of the objects of the present invention is to provide means for efl'ecting a gradual application of the dynamic brake.

Another object of the invention is to adapt a brake of this kind to an automatic or push-button elevator system.

Other objects of the invention will appearhereinafter, the novel combinations of ele-.

ments being set forth in the appended claims.

Referring to the drawings, Figure 1 shows a construction embodying my invention as applied to an automatic elevator system for four floors or landings, the electrical circuits and apparatus being shown diagrammatically; and Fig. 2 is a similar view of a inodificatlon. I I will first describe various features of the system of elevator cont-rol'which are old in the art.

which is to prevent interference between the various push-button switches.

F designates the floor controller which controls the various operating circuits to automatically stop the elevator car at any-predetermined floor or landing. This fioor controller comprises a number of contact strips,

"such as l, 2, 3, 4;, 5 and 6, mounted on an insulating base connected for rotation to some moving part of the elevator machinery, such I v as the winding drum shaft. Thus the insulating base, together with the contact strips mounted thereon, will be rotated when the elevator car is in motion. In the path of the contact strips, and arranged to make contact with them, are the fixed contacts,

such as 50, 51, 52,53, etc, connected to the various conductors leading to the floor controller.

The motor M, here shown as a multiphase alternating current motor, has its stator connected through the leads a, b, 0', reversing switches R, R, mains a, b, c, and switch L to a suitable source of current supply. The reversing switches are operated by the ele'ctro-magnets 10 and 10. 1

An electro-magnetic brake B is adapted to be applied to the motor when the-reversing switches are 'open,,and released by the electro-magnet 9, connected across the leads a, b when one of the reversing switches is closed to supply current to the motor.

A controller Y for. controlling the starting resistance in the rotor circuit of the inc-- tor to eifectthe acceleration of the latter, is operated by the electro-magnet 36.,

The operation of the aforesaid parts in connection with the novel elements of this i invention will be pointed out hereinafter;

Mounted on the motor shaft.7, or'otherwise connected for rotation with the motor M, is the rotor 8. of an auxiliary motor E which acts in opposition to the motor M and is adapted to receive current and operate as an electro dyhamic brake when the motor M is slowing down. The stator of this motor E may comprise a star-connected winding S, having the coils 2d, 25 and 26 connected by the wires 27, 28 and 29, respectively, to the leads a, I and 0' of the motor M.

. A controller X' 'is associated with-the stator S and operates to effect a gradua1'-.ap-

controller comprises sectional resistances cl, 6 and f, g in the circuits of the stator coils 24, 25, 26, and electro- magnets 16, 17, 18 and 19 adapted, when energized, to close shunt circuits around the sectional resistances. The operation of the controller X is under the control of a relay comprising the electro-magnet 35.

A description of the operation of the enthe electrical system, including at the same time a more detailed description of the electrical circuits, will now be given.

The parts are shown in the position they would assume with the elevator car at rest in a, position intermediate the second and third floor landings. It, now, a person at the first floor lamling desires to bring the car down to the first floor, he pushes the button 23 which closes a circuit which may be traced as follows :from the main Z2,

through wire 37 magnet 10, wire 88, contact 50, strip 1, contact 53, coil 7 0, wire 39, floor magnet 40, push-button 23, wire 46, contacts 47, windings 48 and 49 of magnet 5 '45, wire 60 to safety push-button 11 on the car, through the door contacts 30, 31, 32, 33, and wire 61 to the main (1. The coils 48, 49 of the magnet 45 in the circuit just traced are differentially wound so that they substantially neutralize each other when. current is passed'through them in series, and the switch 47 is unaltected by the magnet. The circuit traced, however, also includes the floor magnet 40 which operates to close the switch 62 which in turn closes a circuit through the conductor 63, resistance 64 and coil 49. This circuit is in parallel with the circuit including the contacts 47, push button 23 and coil 48. It is of low resistance, practically short-circuit-ing the latter, with the result that the current which passes through contact 47, push button 23 and coil 40 passes now from coil 49, through re-' sistance 64, wire 63, contact 62 to coil 40, 45, and further, as traced. before. The circuit containing push button 23 and coil 48 consequently gets practically no current. Magnet having only coil 49 active, magnetizes its core andopens switch 47, thereby break- 50 mg the circuit'tlirough the push button 23,

which may consequently be released without affecting the operation. Closing any of the floor push buttons will have no influence on the operation, since all the floor button circuits are broken. Vhile the above. operations are taking place, the magnet 10 operates to close the switch R, bringing the contacts 65, 66 67 into engagement with the fixed contacts 65, 66, 67, respectively. This unites the mains a, Z), and c with the leads a, b and 0 of the motor M and the latter therefore now receives current, in this instance three-phase current. At the same time the brake coil 9 will receive ourrentand lift the brake shoe which is normally held against the other means. Although I have shown a brake magnet operated by a single-phase current, such brake magnet may be a multiphase magnet. The motor starts upon receiving current as 70 stated, with the entire starting resistaice of the controller Y in the rotor circuit at this time. The closing of the reversing switch also closes the circuit of the magnet -coil 36 which is connected by the wire 74 75 to the lead a, and by the normally closed switch 91 and wire 75 to the lead. 0. The core or plunger 76 of the solenoid 36 is now pulled upwardly and carries with it the cam 7 7 which successively closes the switches 78, 79, 80 on one side and the switches 78, 7 9, 80 on the other side. The closing of these switches successively short-circuits the sections of the starting resistances 81 and 82, and the closure of the switches 80, 80 shortcircuits also the resistances S3. A piston 84 of a dash-pot 85 may be connected to the cam 77 to retard the upward movement of the latter. The starting resistance is thus gradually cut out of the rotor circuit of the motor M. At this time the electro- (lynamic brake E exerts no retarding action upon the motor M, as the circuits through the stator S are openat this time at the switch comprising the contacts 86, 87 and the bridging member 94. As the motor M rotates and the elevator car is moved down, the floor controller F rotates slowly in a counter-clockwise direction. As the car approaches the first floor the contact strip 6 on the controller moves into engagement with the stationary contact 52. This closes a circuit as follows :-1trom the lead 6, wire 37, magnet 88, wire 89, contacts 58, 3, 6, 52, switch 90, which at this time is closed, coil 70, conductor 39, magnet 40, switch 62 wire63, resistance 64, coil 49, wires 60, 61

to the main a. Now the contact 50 is connected to one terminal of the reversing switch magnet 10, the other terminal of 1-10 which is connected by wire 37 to the main 6. The coil 88 is therefore connected in parallel to the magnet 10 and operates to .open the switch 91 which open-circuits the magnet 36 and thereby allows the core 76 1 to drop, reinserting the starting resistance of the controller Y in circuit with the rotor of the motor M. Shortly after the contact strip 6 engages the contact 52, the contact strip 5 moves into engagement with the fixed contact 51. This will close a circuit through the relay magnet 35. This circuit may be traced from the lead 6 through wire 28, wire 92, coil 35, wire 93, contact 59, contact strips 4 and 5, contacts 51, 52, switch 90, and thence through coil. 70, wires 39, 63, 60 and 61 to the main a. Thus the relay magnet 35 is connected in parallel to the magnet 10 and operatesto liftthe bridging member 94, into electrical engagement with the contacts 86 and 87. This closes a circuit through the windings 24, and 26 of the stator S. One of these circuits is from the lead Z) through wire 28, winding 25, wire 95, coil 16 and coil 18 to the bridging member 94. Here the. circuit is divided, one branch being by way of the contact 86, resistances d, 6, wire 96, winding 26, wire 29 to the lead 0, and the other branch being through contact 87, resistances f, g, wire 97, winding 24, and wire 27 to the lead a'.- It will therefore be seen that the closure of the switch comprising the bridging member 91 connects together the inside terminals of the stator S, the outside terminals being connected respectively to the leads a, b and c. The resistances 03 and e are in series with the winding 26, the resistances f and g are in series with the winding 2 1, and the coils 16 and 18 are in series with the winding 25. Upon the closure of the switch comprising the co tacts 86 and 87 current will flow through the stator S of the induction motor or electro-dynamic brake E. In other words, the flow of current through the stator S is in such a direction at any instant of time that the induced current in the rotor causes a motor action opposed to the motor M. After the switch comprising the bridging member 94. is closed, the magnets 16 and 18 will close the switches 98 and 99. The interval of time between the connection of the contacts 86, 87 and the closure of the switches 98, 99 may be varied as desired by properly designing the magnets 16 and 18. Upon the closure of the switches 98 and 99 the magnets 17 and 19 will receive current, and since the-resistances of the latter magnets are preferably much less than that-of the conductors (Z and f, the total resistance is materially reduced and a greater current will flow through the stator S, and the dynamic retarding action will be proportionately increased. The magnets 17 and 19 will now receive current to efiect the closure of the switches 68 and 69, thereby short-circuiting the resistances e-an'd g. The electro-dynamic brake motor E will then exert its full power, resistance in the controller X being almost eliminated or reduced to that of the low resistance coils 1.6, 17 18 and 19. These coils remain energized and hold their switches closed and the resistances short-circuited so long as current is supplied to the relay magnet 35.

It will be noticed that the retarding action of the electro-dynamic braking motor E will, for any given condition of the controller X, be substantially proportional to the speed of the motor, so that it the motor M is running at a comparatively high speed as the elevator car approaches the floor landing for which it is destined and the e E is brought into operation, the

net 45. 35- permits the opening of the switch controlled thereby, and consequently the openeffect will be greater than for a slower speed of the motor. This will tend to bring the car uniformly to rest in the same position, even when the speed varies under the action of varying'loads as the car approaches such position. The controller X eifects a gradual application of the brake E, and thus avoids the objectionable efi'ects of suddenly applying the full braking action. The final step in the operation of the floor controller F occurs shortly after the controller X has been brought into operation. This takes place when the strip 1 rides as the contact 53 and opens the circuit through the reversing switch magnet 10. The reversing switch It will thereupon open and cut off current from the motor M and brake magnet 9. The electric power of the motor M will therefore be cut off and-the brake B will be contact 53, the magnets 70 and 40 will also be deenerglzed and current will be cut oil from the winding 49 of the differential mag- The denergization of the magnet ing of the circuits of the stat-9r windings S. The deenergization of the magnet 88 produces the closure of the switch 91, thereby again connecting the terminals of the magnet 36 to the leads a and c in readiness for the next operation. The various circuits are now all open and the parts of the controlling system in their inoperative condition, with the elevator car at the first floor landing.

II" it is desired to bring the elevator car to one of the other landings, the corresponding push- buttonswitch 20, 21 or 22 must be closed, whereupon the operation will be similar to that already described. The direction of movement of the car, however, in this case will be upward, and the direction of the motor must be reversed. This takes place because the reversing switch R is operated by the magnet 10 which is connected by the wire to the-strip 2 of the floor controller, which strip would then be in the push-button circuits. v

If one of the push-button switches in the I car be operated, the operating circuits will be somewhat different. Assuming again that the parts are in the positions shown and the push-button 15 in the car is operated, a circuit will be closed from the main 6 through wire 37, magnet 10, wire 38, con-- magnet 4:0 operates to close the switch 62 which in. turn closes a circuit through the wire and resistance 6 in parallel with the magnet n and push-button 15. The coil 10 eilccts the opening of the switch 47 and prevents interference from push-buttons at the tloor landings. The safety car magnet 4 1 closes the switch 10 1, which completes a. circuit from the main 6 through wire 92,.

the comparatively high resistance 105, switch 104, coils 1 1, 19,wirc 60,push-button switch 11, door switches 30, 31, 32, 33, and wire 61 to the main a. This circuit connected across the mains b and a can now be opened only by the switch 11 in the car, or by one of the door switches 30, 31, 32 ,or 33. Thus after the car has been brought to a full stop by the automatic operation of the floor controller F, the circuit which includes the safety magnet coils 1a and 19 will remain closed and the switch 47 will be held open and so render ineffective any operation of the landing switches 20, 21, 22, 23 until the landing door has been opened and closed again or until the switch 11 is opened and closed, to restore the system to its original condition.

In Fig. 2 I have shown a somewhat modified construction,particularly of the electrodynamic brake and the controller therefor. The electro-dynamic brake in this instance consists of a small series wound generator G, the armature of which is connected directly to the shaft of the motor M, but may be connected to other moving parts of the elevator machinery, such, for instance, as the intermediate mechanism between the motor and the hoisting drum. In order that the direction of current through the generator G may be reversed when the motor M is reversed, and thus maintain the proper connection of the generator for self-excitation, I provide auxiliary switches R R in the generator circuit. These auxiliary switches are in this instance controlled by the magnets 10 and 10. The cores or plungers of the magnets-10 and 10 have vertically depending rods or extensions 105, 106 which carry the insulated contacts 107, 108 and 109,110 arranged to engage the stationmy contacts 111, 1 and 1 respec'i tively. The lever 115 pivoted at 116 is in this instance shown with lateral pins or projections at its ends extending into vertical slots in the lo'\\.' .:-r ends of the rods 105, 106. This lever operates to hold one of the reversing switches R or R always open, as well as toprevent both the main reversing switches R and R being closed at the same time. The controller X for the generator G comprises in this instance a sectional resistance cl, 6 adapted to be sho'rt-circuited by the operation oi the magnets 10, 17. Any desired number of these magnets and sections of resistance may be used to secure any degree of refinement in the operation of the generator G The construction of the controller Y for the rotor of the motor M is substantially the same as the controller Y shown in Fig. 1, and its operation will be readily understood from an inspection of the drawing Without a detailed description.

The sectional resistances S1 and 8 2 are gradually short-eircuited by the bridging member 77 as it is drawn up by the action of the magnet 36. The resistance 83 is also short-circuited by the strip 77 when the latter is in its uppermost position.

Any other suitable term of controller than those shown may be used, if desired. The form of the controller and starting resistance depends also on the type of motor .apparatus when used in connection with the push-button circuits of Fig. 2 will be given, however. If the push button, say that designated 23, is operated, a circuit will be closed through the reversing switch magnet 10 and the latter will close the switch R to connect the source of current supply to the motor M and the brake magnet 9. The brake will therefore be released and the motor will run at slow speed with the starting resistances 81 82 and 83 in circuit. The closure of the switch also efiects the energization of the magnet 36 which then operates to gradually cut out the starting resistances 81, 82 and 83 and bring the motor up to full speed. At this time the circuit to the generator G- is open at the contacts 86 and 87 so that it does not exert any retarding effect on the motor, but, on the contrary, runs freely. As the elevator car approaches the selected floor landing, the contact strips 6 and 5 on the floor controller close first the circuit. of the magnet 88 which thereupon opens the switch 91 to ett'ect the denergization of the magnet 30. The starting resistances of the controller Y will then i be reinserted in the rotor circuit of the moon the speed of the motor M now flows through this circuit and the generator exerts a retarding effect on the motor proportional to the strength of such current. The relay magnet 16' in this circuit now operates to the generator circuit and increasing the cur-- rent therein. The magnet 17 closes the switch 129 which short-circuits the resistance 6, thereby reducing the total resistance of the generator circuit to a minimum and permitting the full braking efiect of the external power consuming device to come into play. The retarding action of this external ways. Multiphase magnets, such as shown,-

power consuming device will depend upon the speed of the motor M, as pointed out in connection with the operation of the brake E shown in Fig. 1. In the present instance the current strength in the generator circuit will depend upon the speed of the generator, but will not be proportional to the speed, for the voltage of the series wound generator will build up more rapidly than the increase in the speed of the generator, owing to the increase in field strength as well as the increase in speed of the armature.

This will result in an increase of the retarding action in a greater ratio than the increase of speed of the motor. But the retarding action required to bring the moving parts to rest within a given distance also increases at a greater ratio than the increase of speed of'said parts. This increased retarding action of the generator for an increase of speed is therefore advantageous in bringing the parts uniformly to rest within a given distance even when the speed of the motor is affected by the load. The generator G may be designed to produce this variation in any desired degree, such variation being reduced to a minimum by having a shunt winding producing a saturated magnetic field even at'low speeds.

The reversing switches R and It operate to change the connections of the armature brushes 120, 127 relatively to the field winding 123 whenever the current through the motor M is reversed. That is, with the switch It closed, the upper brush 120 is connectedto the upper terminal of the field coil 123 and the lower brush 127 is connected to the lower terminal of the field coil;

but when the switch R is closed the upper-and lower armature brushes are connected respectively with the" lower and upper terminals of field coil 12?). But the direct-ion ofrotation of the armature is also reversed when the reversing switches have been changed, so that the current through the field winding isalways in the same direction, but changes direction in the armature so that the generator is'always selfacting.

Although I have shown my invention as including a particular form of elevator system, obviously it may be varied in many nets are operated by alternating current.

The magnets are shown in Figs. 1 and 2 as single-phase for the sake of simplicity and clearness. Furthermore, I do not wish to be limited to the particular form of electrodynamic brakes and controllers therefor which I have shown, as other forms may be devised. Obviously various changes in the details of construct-ion and arrangement of parts may also be madeby those skilled in the art without departing from the spirit and scope of my invention, and I desire therefore not to be limited to the precise constructions shown. Having thus fully described my invention, what I wish to have protected by Letters Patent of the United States is 1. The combination with a motor, of an mally open circuit, resistance in the circuit, means for closing said circuit, and means operative upon the closure of said circuit to reduce said resistance.

2. The combination with a motor, of an. electro-dynamic brake comprising a normally open circuit, a sectionalresistance in said circuit, means for closing the circuit, and means operative automatically upon the closure of said circuit to successively shortcincuit the sections of resistance.

3. The combination with a motor, of an electro-dynamic brake, a resistance in acircuit ofthe brake, a relay controlling said circuit, and means controlled by said relay for effecting a gradual reduction of the resistance in said circuit.

4. The combination with a motor, of a series generator directly connected to the motor, means to close the generator circuit and cause the same to act asa brake on the m0- tor, and means for varyingthe resistance in said circuit to the generator.

5. The combination with a motor, of an electro-magnetic brake, an electro-dynamic brake, and automatic means for applying the brakes successively and releasing one brake when the other is applied.

a vary the braking action of 6. In an automatic elevator system,- the combination with a motor, of an electrodynamic brake, and a floor controller controlling the application of said brake.

7 In an automatic elevator system, the combination with a motor, of an electroplication of the brake, and a floor controller controlling the relay.

8. In an automatic elevator system, the combination with a motor, of a retarding d namic brake, a relay controlling the apdevice fo'rthe motor, and a floor controller controlling said retarding: device.

9. In an automatic elevator system, the combination with a motor, of an electrodynamic brake, means for efi'ecting a gradual application of said brake, and a floor controller controlling said means.

10. In an automatic elevator system, the

combination with a motor, of an electrodynamic brake having a normally open circuit, means for closing said circuit, and a floor controller controlling said means.

1.1. In an automatic elevator system, the combination with a motor, of an electrodynamic brake, a floor controller, and means controlled thereby for varying the resistance in the electric circuit of said brake.

12. In an automatic elevator system, the combination with a motor, of an electrodynamic brake comprising a normally open circuit, a resistance in the circuit, a floor controller, and meanscontrolled thereby to close said circuit and then reduce the resistance therein.

13. In an automatic elevator system, the combination with a motor, of an electrodynamic brake, a controller therefor, and a floor controller associated with said firstnamed controller.

14:. In an automatic elevator-system, the combination with a motor, of an electro dynamic brake, a controller in circuit with the brake, an electro-magi'letic relay controlling said circuit, and a floor controller controlling said relay.

15. In an automatic elevator system, the combination with a motor, of a generator associated therewith, a floor controller, and a controller for the generator under the controlof the floor controller.

16. In an automatic elevator system, the combination with a motor, of a series wound generator, a floor controller, and means'associated therewith for controlling the circuit of the generator.

17. In an automatic elevator system, the combination with a motor and motor-controlling apparatus, of an electro-dynamic brake and controlling mechanism therefor, and a floor controller for controlling the oporation ot' the said motor-controlling apparatus and said brake-controlling mechanism.

18. In an automatic elevator system, the combination with a motor, of a controller there-for, an electro-dynamic brake, a coni troller therefor, a floor controller, and electrical connections between the said parts.

19. In an automatic elevator system, the

combination with a car, of a motor, an electro-dynamic brake for the motor, means for controlling the'operation of the motor to bring the car to rest at any predetermined floor landing, and means to automatically apply said brake when the car reaches a point within a certain distance oft said floor landlng.

. 20. In an automatic elevator system, the

combination with a motor, of a car, means for controlling the operatlon of the motor to bring the car to any predetermined floor landing, an electro-dynamic brake, and

button circuits controlling the operation of the motor, an electro-dynamic brake for the motor, and means associated with said circuits for controlling the operation of said brake.

22. In an automatic elevator system, the 8 combination with a motor, of a car, pushbutton circuits corresponding to the several floor landings and controlling the operation of the motor, a floor controller included in. said circuits, an electro-dynamic brake for the motor, and means controlled by the floor controller for operating said brake when the car approaches the floor landing corresponding to the push-button operated.

23. In an automatic elevator system, the combination with a motor, of an electrodynamic brake, an electro-magnetic brake, a floor controller, and means controlled by said floor controller for operating the electro-dynamic brake and then simultaneously 9 releasing the electro-dynamic brake, opening the motor circuit, and applying the electro-magnetic brake.

24. The combination with a motor, of an electro-dynamic brake, reversing switches,

and circuit connections from the motor'and said electro-dynamic brake to each of said i reversing switches.

. 25. In an automatic elevator system, the combination withsa car of an electric motor, switches corresponding to the floor landings,

an electro-dynamic brake, and controllin mechanism operative when one of said switches has been operated to bring the car to the corresponding floor landing, and automatically apply said electro-dynamic brake asthe car approaches said landing.

26. In an automatic elevator system, the combination with a motor, of an electrodynamic brake, an electro-magnetio relay controlling the brake circuit, and a floor controller controlling said relay 27. In an automatic elevator system, the combination with a car, of a motor, pushbutt-on circuits corresponding to the several floor landings, a floor controller associated with said circuits, electro magnetic reversing switches for the motor, an electro-magnetic brake having its circuit connected to the motor circuit between the motor and the reversing switches, an elect-ro-dynamic brake, a sectional resistance in the electro-dynamic brake circuit, electro-magnetic relays con' trolling said resistance, an electro-magnetic switch controlling said relays and thecircuit 130 for operating thefloor cont-roller in unison with theelevator car,'and circuit connections extending to the controller and controlled tliereby to'successively operate in the following order when a push-button circuit has been closed, first to close a circuit through a reversing switch magnet whereby a reversing switch is closed and current supplied to the motor and electro-magnetic brake, and the starting resistance cut out of the motor circuit, second, as" the car approaches the floor landing corresponding to the push-button circuit operated, to close a circuit,- controlling the starting resistance 1 and cause said resistance to be reinserted in Copies of this patent may be obtained for the motor circuit, thir d,':',to' -c'lose a circuit through the electro-magnet; ofsaid switch controlling the circuit of theelectro-dynamic brake and eflect a closing of the electrodynamic brake circuit, and the cutting out of the sectional resistance in said circuit, and, fourth, to open the circuits leading to the controller and thereby effect the opening of the reversing switch, the application of the electro-magnetic brake, and restoration of parts totheir normal condition.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing Witnesses.

JOHN D. IHLDEB WVitnesses C. BLINN,

JAMES Gr. BETIIELL.

five cents each, by addressing the Commissioner of Iatents, Washington, D. G.

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