US548829A - Device for regulating current admitted to electric motors - Google Patents

Description

(No Model.) 3 Sheets-Sheet 1.

P. E. HERDMAN. DEVICE FOR REGULATING CURRENT ADMITTED TO ELECTRIC MOTORS.

No. 548,829. Patented Oct. 29,1895.

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Attorney.

ANDREW KGIAHAM. FHD'I'O-LHHD.WASHINGTON. DYE.

(No Model.) '3 SheetSSh6et 2. P. E. HERDMAN. DEVICE FOR REGULATING CURRENT ADMITTED T0 ELECTRIC MOTORS.

No. 548,829. Patented Oct. 29,1895.

Inventor;

Q I Attorn'ey.

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AN DREW B GRAHAM. PHUTOLITHQWASHINGTOMD C,

3 Sheets-Sheet 8.

(No Model.)

F. E. HERDMAN. DEVICE FOR RBGULATING CURRENT ADMITTED T0 ELECTRIC MOTORS.

Patented Oct. 29, 1895.

Inventof.

Witnesss.

\ .4IlflWlffi/llIll/Ill!!!IIIIIIIIIIIIIIIIIIII Attorney.

ANDREW B GRAHAM. PHUTO-UTHQWABHINGTON] c.

UNITED I STATES PATENT OFFICE.

FRANK E. HERDMAN, OF WINNETKA, ILLINOIS.-

DEVICE FOR REGULATTNG CURRENT ADMITTED TO ELECTRIC MOTORS.

SPECIFICATION forming part of Letters Patent No. 548,829, dated October 29, 1895.

Application filed March 22, 1895.

T0 at whom it may concern.-

Be it known that I, FRANK E. HERDMAN, a citizen of the United States, residing at Vt innetka, county of Cook, and State of Illinois, have invented a new and useful Improvement in Devices for Regulating Current Admitted to Electric Motors, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, which form a part of this specification.

In the use of electric motors supplied from a power-station it often occurs that the powerstation places restrictions that will not permit beyond a certain number of amperes to be initially admitted at the first closing of the switch, and additional amperes have to be taken gradually. Thus if the initial amount be ten amperes and the motor requires fifty amperes to do its full work it is necessary to provide means to allow the increase to occur gradually. If a device such as is shown in Letters Patent No. 530,773, issued to me December 11, 1894:, in which a solenoid in the circuit to the armature is used to control the speed with which the resistance is cut out, should be used alone, the solenoid would have to act at ten amperes, and any current admitted beyond that would have to be admitted so gradually as to make it objectionable, for in the device of that patent the retarding effect produced by the solenoid when energized remains, and the remainder of the movement of admission of current above the amount for which it is adjusted would have to be against this set retarding eifect. \Vhile, broadly considered, this would prevent the admission of current beyond the initial amperage, except in a gradual manner, still it would cause such a sluggish movement of the motor undera light load as to be very objectionable. This is especially objectionable where the motor is used in connection with an elevator, which has attimesaheavyload and at other timesalight load. Whentheloadislight,themotorshould have the capacity to get under way as rapidly as possible. Of course when heavily loaded it is not expected to get under way rapidly. If

the device of Patent No. 530,773 be used alone and without modification and the solenoid is adjusted for a given current-say ten ampres-then any load requiring a greater current would cause a certain retarding effect and make the admission of the current proper for of the power-station.

sees no. 542,752. (No model.)

such load; but'with a light load, which would require only ten amperes, the same action would take place and, being unnecessary, is objectionable in that it retards the time in which under those conditions the motor gets under Way.

The device forming the subject of this invention while the same in principle and containing the broad invention described and claimed in PatentNo. 530,773, still has certain additions and modifications which especially adapt it to overcome the above defects and is applicable for the purpose enumerated. In general its construction and operation permit the initial amount of current-ten amperes, or whatever the required amount may be-to be admitted on the first closing of the switch, and then permit predetermined increments beyond this to be admitted successively and gradually to meet the requirements If, for instance, the load would require fifty amperes to start it, then this device would admit it gradually un til the fifty amperes are admitted, the graduation being governed by that which is permitted by the power-station; but as soon as this maximum current is reached then the further admission would be prevented; but the resistance in the armature-circuit would be cut out as rapidly as possible without causing further increase. If there were a light load on the motor-where, for instance, only ten or twenty amperes were required to start it-the operation would be the same as before until the ten or twenty amperes were ad mitted,when the resistances would be cut out of circuit as rapidly as possible without causing the ingo crease of current to be more rapid than the requirements of the power-station, the point in this case being that the device regulates the admission of the amount of current to the motor sufficient to start it, so that it shall be ad 5 mitted only in the time predetermined for its admission. The devicefor accomplishing this is shown in the accompanying drawings, in which Figure 1 is a front view of the device attached to a motor. Fig. 2 is a diagram showing the wiring. Fig. 3 is a side elevation of the device. Fig. 4 is a section on line 00 0c of Fig. 3. Fig. 5 is a section on linew'w of Fig.

4. Fig. 6 is a plan view of a modified form. Fig. 7 is a section on line y y of Fig. 6.

A is an electric motor; 13, its armature; O, the field-magnet, the wires from the source of current-supply passing directly to the fields.

D is the armature-controlling switch, and is of the type described in Letters Patent No. 519,120, and d is the shaft for operating said switch.

d d are the brushes by which the current from the two poles of current-supply passes to the switch D, and from the brushes d d the current is led to the solenoid E, the core 0 of which is connected to resistance-arm F, having the brush f.

g is a plate in electrical connection with the resistances and with brush d The arm F is in electrical connection with the armature through solenoid I, and the armature is in electrical connection with the other pole of current-supply by wire connecting with brush d of switch D.

Speaking generally, when the switch is 0perated the current is admitted to solenoid E, energizing it and causing the arm to travel over the resistances, admitting current to armature through resistances, which are gradually cut out until the arm or brushfreaches the plate 9, when the full force of the current passes to the armature.

Speaking now of Figs. 8, 4, and 5, H is a dashpot connected to the lower end of the core of solenoid E by means of the side bars 72. II is piston of this dash-pot, and is connected by the means of its piston-rod h with the frame holding the solenoid E. In the piston-rod of the dash-pot II is placed a valve W, the valvestem 71,3 of which. is connected to one end of the centrally-fulcrumed rocker J, the other end of the rocker being attached to the core of solenoid I. K is a spring, which is set to act against or resist the movement of the core of solenoid I. This spring is so adjusted that the distance the core of solenoid I is drawn upward is directly proportional to the amount of current passing to the armature. Thus if the solenoid I is adjusted for ten (10) amperes, then when it is excited by ten amperes the spring would be compressed a certain fixed amount, and each additional ten amperes of current passing through the solenoid I will cause the spring to be compressed an additional and like amount. The piston II of the dash-pot H has within it the secondary piston H provided with an opening 77. through it, regulated by the screw it. This piston has a sleeve h, surrounding the piston-rod h. In the piston-rod it of dash-pot H is a slot formed between the points k, and in the sleeve 71 isaslot between the points 70 7a. A pin Ii, connected to the valve-stem h works in this slot. Normally the pin L rests at the top of the slot and holds the secondary piston I1 The piston-rod 7L is hollow, and in the piston-rod are a number of ports 1 2 3 4 5 above the piston, the port 1 being open and the ports 2 3 4t 5 being closed by the secondary piston H at the beginning of the operation. WVhen the switch is operated, the solenoid E is energized 'crement the same operation takes place,

ance-arm is prevented; but as this movement has also released the pin from holding the secondary piston II it falls, the speed of its fall being determined by the extent of outlet formed by the adjustment of the screw it. As soon as the secondary piston II has fallen sufficiently to uncover port No. 2, the solenoid E again commences to act, and acts until the solenoid I has received a second increment of current sufficient to compress the spring K enough to again force downward, through the medium of the rocker, the valve-stern 7L3 and valve 712, so as to cover port No. 2, at which time the sleeve of the secondary piston H is relieved from the pin, with which it again came in contact at the end of its previous downward movement. The length of the slot between the points k 70 being sufficient to allow the piston H to move sufficiently to open the port, it again moves downward until it opens port No. 3, at which time the solenoid again acts. This is continued until the necessary amperage is admitted.

In order to prevent the motor receiving too much current-thus, for instance, if fifty amperes is the limit which it is desired to pass to the motor-then the arrangement is such that the valve covers the lowest port when the solenoid I has been energized sufficiently to compress the spring an amount equal to fifty amperes, and as the secondary piston 11 in the downward movement has no other ports to uncover there can be no further movement of the solenoid E. By this construction it will be seen that by means of the solenoid I, the rocker J, the spring K, and the valve 712 the machine initially is only allowed to receive a certain increment of current, and by means of the adjustment of the screw h5 in the secondary piston H the time may be determined which shall be allowed before the machine receives any additional increment of current, and can be adjusted exactly to the time required for an additional increment in the current passing, and for each succeeding in- In consequence, if a machine requires, say, fifty amperes to get under way the admission of current at the first closing of the switch cannot exceed ten amperes. Then the time at which the fifty amperes would be admitted to the machine would be regulated by the passing of this secondary piston over the successive ports, the solenoid I being energized proportionately by each increment of current until it compresses the spring K a suitable amount.

Thus the speed with which the'rheostat-arm passes over the contacts is not set for any amount of resistance, but simply according to the increment of current-that is, if ten amperes is admitted to the motor and the motor is so slow in getting under way that the rheostat-arm would only move, say, two or three contacts before the current would be increased to the amount of the increment then the action of this device would be such as to prevent its going farther until the secondary piston had opened another port. If the next increment will permit the motor to get under way and develop a counter electromotive force, so that a greater amount of resistance could at this time be cutout, then that am ount can be cut out, as the distance which the rheostat-arm passes is only controlled by the amount of current passing to the armature. Thus if ten amperes would start the machine and develop its counter electromotive force then as soon as the solenoid I has checked the dash-pot long enough for these ten amperes to perform their Work it would permit the rheostat-arm to pass over the resistances as quickly as the mechanism could carry it.

In Figs. 6 and 7 I have shown a modified form, in which, as before, E is the solenoid controlling and operating the resistance-arm F. H is a dash-pot connected to the core of the solenoid, and h is a piston, the rod of which is connected to the frame carrying the solenoid, there being an opening from one side to the other of the piston. h is a valvestem connected to the rocker J, and between the connection of the valve-stem to the rocker J and the frame is a springj. This rocker J instead of having, as in the other case, a fixed fulcrum is pivotally connected at its center to the valve-stem h and at one end to the core of the supplemental solenoid I, and K is a spring against which the core of the supplemental solenoid I works, as in the former case, the other end of the rocker being connected to the piston rod h of a piston M in a secondary dash-pot M. M is a pin adjustable in a stand, and is in alignment with the rocker J in its movement. The operation of this modification is as follows: When the solenoid I is energized sufficient to compress the spring K an equivalent to the increment of current desired to be admitted, it forces down the valve-stem 77. compressing the springj and closing the port in the piston H of the dash-pot II. This is accomplished with the rocker acting as fulcrumed upon its connection with the end of the piston-rod h of the supplemental dash-pot M. As soon as this is down the spring j commences to act and acts upon the rocker, so that it swivels on its connection with the core of the solenoid I and lifts the piston-rod and piston of the supplemental dash-pot M. The speed with which said piston is lifted is determined by the adjustment of the screw it, controlling the orifice between one side and the other of the piston II in the supplemental dash-pot M. This upward movement of thespring forces up the valve-stem 7L2, again opening the port of the piston in the main dash-pot H, and the solenoid I again acts to move the rheostat-arm.

In order to prevent too great an amount of current being admitted by the adjustment of the screw M, a further movement of the piston of the supplemental dash-pot M may be prevented after the rocker in its previous movement has reached contact with the screw.

Having now fully described my invention, what I claim, and desire to protect by Letters Patent, is-

1. The combination with a translating device, electric connections from a source of current supply to said translating device, resistances in the said circuit to the translating device, an arm for controlling said resistances, of a device adapted to retard the movement of said arm over said resistances, mechanism connected with said retarding device adapted when operated to render said retarding device capable of preventing the movement of said arm, and a solenoid in the circuit to the translating device, operatively connected with said mechanism, the arrangement and connection being such that when the solenoid receives a predetermined increment of current the mechanism is operated.

2. The combination with a translating'device, electric connections from a source of current supply to a translating device, resistances in the said circuit to the translating device, an arm for controlling said resistances,

of a device adapted to retard the movement of said arm over said resistances, mechanism connected with said retarding device adapted when operated to render said retarding device capable of preventing the movement of said arm, and a solenoid in the circuit to the translating device, operatively connected with said mechanism, the arrangement and connection being such that when the solenoid receives a predetermined increment of current the mechanism is operated, a supplemental device adapted to be brought into action when said mechanism is operated and return the retarding device to its normal mechanical resistance.

3. The combination with a translating device, electric connections from a source of current supply to said translating device, resistances in the said circuit to the translating device, an arm for controlling said resistances, of a device adapted to retard the movement of said arm over said resistances, mechanism connected with said retarding device adapted when operated to render said retarding device capable of preventing the movement of said arm, and a solenoid in the circuit to the translating device, and operatively connected with said mechanism, the arrangement and connection being such that when the solenoid receives a predetermined increment of current, the mechanism is operated, a supplemental device adapted to be brought into action when the mechanism is operated and return the retarding device to its normal mechanical resistance, the construction of said supplemental device being such that it acts to return said retarding device to its normal resistance in a predetermined time.

4. The combination with a translating device, electric connections from a source of current supply to said translating device, resistances in the said circuit to the translating device, an arm for controlling said resistances, of a device adapted to retard the movement of said arm over said resistances, mechanism connected with said retarding device adapted when operated to render said retarding device capable of preventing the movement of said arm, a solenoid in the circuit to the translating device, and operatively connected with said mechanism, the arrangement and connection being such that when the solenoid receives a predetermined increment of current the mechanism is operated, a supplemental device adapted to be brought into action when the mechanism is operated and return the retarding device to its normal mechanical resistance, the construction of said supplemental device being such that the time in which it acts to return said retarding device to its normal resistance may be varied by previous adjustment.

5. The combination with a translating device, electric connections from a source of current supply to said translating device, resistances in said circuit to the translating device, of an arm for controlling said resistances, a device adapted to retard the movement of said arm over said resistances, mechanism connected with said retarding device adapted when operated to render said retarding device capable of preventing the movement of said arm, a solenoid in the circuit to the translating device, and operatively connected with said mechanism, the arrangement and connection being such that when the solenoid receives the predetermined increments of current its core is moved a fixed amount, and the retarding device is rendered capable of preventing the further movement of said arm, a supplemental device adapted to be brought into action at each time the retarding device is so acted on, and return the retarding device to its normal resistance.

6. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, an opening between the two sides of the piston in the said dash pot, a valve for closing said opening, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem of the valve of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that when a predetermined increment of current is admitted to the translating device, said core is operated so as to move the valve to close the opening in the piston of the dash pot of the first solenoid.

7. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electric connections to said solenoid, a dash pot for controlling the movement of said solenoid, two openings between the sides of the piston in said dash pot, valve for closing said openings, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem of the valve of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that when a predetermined increment of current is admitted to the translating device, said core is operated so as to operate said valve stem to close the opening in the piston of the dash pot of the first solenoid, a supplemental piston, having an orifice, sustained by the valve stem and in the initial operation adapted to close the lower of the two ports, and to be released from the valve stem when the valve stem is operated by the secondary solen oid, and move downward and uncover the lower port.

8. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, two openings between the sides of the piston in said dash pot, valve for closing said openings, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem of the valve of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that when a predetermined increment of current is admitted to the translating device said core is operated so as to operate the valve stem to close the opening in the piston of the dash pot, of the first solenoid, asupplemental piston, having an orifice, sustained by the valve stem and in the initial operation adapted to close the lower of the two ports, and to be released from the valve stem when the valve stem is operated by the secondary solenoid, and move downward and uncover the lower port, a regulat ing screw in said orifice in the supplemental piston.

9. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuitto the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming connections from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the secondary solenoid and the valve stem of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that with the admission of successive predetermined increments of current to the translating device, the core is operated so as to operate the valve stem to cause the valve to close successively the ports in the piston of the first solenoid dash pot.

10. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connection to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming connections from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem, of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that with the admis sion of successive predetermined increments of current to thestranslating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston, having an orifice, sustained by the valve stem and, in the initial operation, adapted to close all but the upper port and successively to be released in the successive movement of the valve stem and move downward a distance to uncover a port next below the port closed in the successive movement of the valve stem.

11. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connection to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming a connection from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the secondary solenoid and the valve stem of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that with the admission of successive predetermined increments of current to the translating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston, having an orifice, sustained by the valve stem, and in the initial operation adapted to close all but the upper port and successively to be released in the successive movements of the valve stem, and move downward a distance to uncover a port next below the port closed in the successive movements of the valve stem,the arrangement being such that when the desired limit of increment of current has been reached the supplemental piston is below the lowest port in the dash pot piston.

12. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming connections from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the secondary solenoid and the valve stem, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that with the admission of successive predetermined increments of current to the translating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston, having an orifice, sustained by the valve stem, and, in the initial operation, adapted to close all but the upper port, aslot in the piston rod of first mentioned piston, a slot in the said piston rod of the supplemental piston, a pin connected to the valve stem and projecting within the slot in the supplemental piston and adapted to sustain the supplemental piston when the valve stem is at rest, but when the valve stem moves the supplemental piston is released.

13. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming connections from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem of the dash pot of the first solenoid, a mechanical resistance device acting against the movement of the core of the second solenoid, said mechanical resistance device being regulated so that with the admission of successive predetermined increments of current to the translating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston, having an adjustable orifice, sustained by the valve stem and in the initial operation adapted to close all but the upper port, a slot in the piston rod of first mentioned piston, a slot in the piston rod of the supplemental piston, a pin connected to the valve stem and projecting within the slot in the supplemental piston and adapted to sustain the supplemental piston when the valve stem is at rest, but when the valve stem moves the supplemental piston is released.

14. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm, and electrical connections to said solenoid, a dash pot for controlling the movementof said solenoid, an opening between the two sides of the piston in said dash pot, avalveforclosingsaidopening, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the said valve stem, a spring acting against the movement of the core of second solenoid, said spring being regulated so that when a predetermined increment of current is admitted to the translating device, said core is operated so as to cause the valve stem to operate the valve to close the opening in the piston of the dash pot of the first solenoid.

15. In combination with a translating device, electrical connections from a source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connection to said solenoid, a dash pot for controlling the movement to said solenoid, two openings between the sides of the piston in said dash pot, valves for closing said openings, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem, a spring acting against the movement of the core of the second solenoid, said spring being regulated so that when a predetermined increment of current is admitted to the translating device said core is operated so as to cause the valve stem to operate the valve to close the opening in the piston of the dash pot of the first solenoid, a supplemental piston, having an orifice, sustained by the valve stem and in the initial operation adapted to close the lower of the two ports, and to be released from the valve stem when the valve stem is operated by the secondary solenoid, and move downward and uncover the lower port.

16. In combination with a translating device, electrical connections from the source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, two openings between the sides of the piston in said dash pot, valves for closing said openings, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem, a spring acting against the movement of the core of the second solenoid, said spring being regulated so that when a predetermined incrementof current is admitted to the translating device said core is operated so as to cause the valve stem to operate the valve to close the opening in the piston of the dash pot, of the first solenoid, a supplemental piston, having an orifice, sustained by the valve stem and in the initial operation adapted to close the lower of the two ports, and to be released from the valve stem when the valve stem is operated by the secondary solenoid, and move downward and uncover the lower port, a regulating screw in the orifice, in the supplemental piston.

17. In combination with a translating device, electrical connections from the source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming connections from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem, a spring acting against the movement of the core of second solenoid, said spring being regulated so that with the admission of successive predetermined increments of current to the translating device the core is operated so as to close successively the ITO ports in the piston of the first solenoid dash pot.

18. In combination with a translating device, electrical connections from the source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other, forminga connection from one side to the other of the piston in said dash pot, a valve adapted in its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem,ofthe dash pot, of the first solenoid, a spring acting against the movement of the core of second solenoid, said spring being regulated so that with the admission of successive predetermined increments of current to the translating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston, having an orifice, sustained by the valve stem and in the initial operation adapted to close all but the upper port and successively to be released, in the successive movements of the valve stem, and move downward a distance to uncover a port next below the port closed in the successive movements of the valve stem.

19. In combination with a translating device, electrical connections from the source of current supply to said translating device, resistances in the circuit to the translating device, an arm for controlling said resistances, a solenoid to operate said arm and electrical connections to said solenoid, a dash pot for controlling the movement of said solenoid, a series of ports one below the other forming a connection from one side to the other of the piston in said dash pot, a valve adaptedin its movement to successively close said ports, a valve stem, a secondary solenoid in series with the translating device, connection between the core of the second solenoid and the valve stem, a spring acting against the movement of the core of the second solenoid, said spring being regulated so that with the admission of successive predetermined increm cuts of current to the translating device, the core is operated so as to cause the valve stem to operate the valve to close successively the ports in the piston of the first solenoid dash pot, a supplemental piston having an orifice sustained by the valve stem, and in the initial operation adapted to close all but the upper port and successively to be released, in the successive movements of the valve stem, and move downward a distance to uncover the port next below the port closed in the successive movements of the valve stem, the arrangement being such that when the desired limit of increments of current has been reached the supplemental piston is below the lowest port in the dash pot cylinder.

20. The combination with a translating device, electric connections from a source of current supply to said translating device, a device for admitting the current to said translating device, mechanism adapted to control the operation of said current admitting device, said controlling device being so adjusted that when the translating device receives a predetermined increment of current said current admitting device is held from further acting.

21. The combination with a translating device, electric connections from a source of current supply to said translating device, a device for admitting the current to said translating device, mechanism adapted to control the operation of said current admitting device, said controlling device being so adjusted that when the translating device receives a predetermined increment of current said current admitting device is held from further acting, and means to automatically release said controlling device.

22. The combination with a translating device, electric connections from a source of current supply to said translating device, a device for admitting the current to said translating device, mechanism adapted to control the operation of said current admitting device, said controlling device being so adjusted that when the translating device receives a predetermined increment of current said current admitting device is held from acting, the operation being such that with successive predetermined increments of current, said current admitting device is held from acting and intermediate thereto is released from the control of said controlling device.

In testimony of which invention 1 have hereunto set my hand.

FRANK E. HERDMAN. Witnesses:

J. M. OWEN, H. E. TURNER.

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