US1919991A - Electroresponsive time element device - Google Patents

Description

July 25, 1933. G B, STARE 1,919,991

ELECTRORESPONSIVE TIME ELEMENT DEVICE Original Filed May 4. 1925 Inventor:

Patented July 25, 1933 UNITED GEORGE B. STARIE, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRORESPONSIVE TIME ELEMENT DEVICE Original application filed May 4, 1925, Serial No. 28,036, new Patent No. 1,720,613, dated July 9, 1929.

Divided and this application filed July 26, 1926. Serial No. 125,112.

The present application is a division of my former application, Serial No. 28,036, filed May 4, 1925 and patented July 9, 1929, No. 1,720,613, on time element devices'and motor control systems employing the same, the present application being for the purpose of securing patent protection on the electromagnetic time element device of sald former application which discloses said device and a system of motor control embodying the same.

My invention relates to an improved electroresponsive time element device for gen eral purposes, and in particular to an electromagnetic time element. device for controlling the operation of a motor controlling switch after the operation of another motor controlling switch.

Time element control of electromagnetic switches, as heretofore proposed, has left something to be desired in the way of a simple, reliable and effective device which invariably gives the desired time interval of operation. Motor control systems operating on the time element principle, as heretoiore proposed, have also left something to be desired in that complications are introduced wihch render the system uncertain in operation.

In carrying my invention into effect, I employ an electromagnetic time element device of very simple construction, and one which when employed in a motor control system, for example, makes possible a very simple, effective and reliable system for producing the intended control of the motor. The electromagnetic time element switch is provided with a magnetic structure with a winding thereon proportioned to set up an excessively high value of magnetic flux which stores the electromagnetic energy for producing the time delay action. The magnetic structure includes a magnetic movable element or armature carrying a switch contact, the armature being biased to the unattracted position and the switch contact carried bythe armature being biased to a definite position, as for example, the closed position. The armature of the electromagnetic in time element device is biased to the unattracted position by any suitable means such as a spring, the tension of which may be adjusted so that when the armature, is in the attracted position, it is magnetically held in that position against the action of the spring tending to move the armature to'the unattracted position. tromagnet is connected so as to be shunted or short circuited in order to produce the desired time delay operation of the contact. By reason of the stored electromagnetic energy the winding has a considerable inductive effect. Thus the short-circuiting of the winding will produce an induced current to maintain the excessive value of magnetic flux in the magnetic structure of the electromagnet and thus maintain the armature in the attracted position for an appreciable interval of time during which the excessive value of flux producing the induced current persists. The winding is provided with a suflicient number of turns so that with the armature in the attracted position, the magnetic flux of the relay will be many times in excess of that required to hold the armature in the attracted position, thus insuring that the time interval introduced will not be appreciably affected by such variables as variations of the-supply circuit potential or variations of the heating-of the winding. Adjustment of the time element is obtained by adjusting the air gap between the armature and the core of the electromagnet, and this is preferably done .by mounting a shim of non-magnetic material on the armature so that when the armature is magnetically op erated to the attracted position, the shim will insure that there will be a definite and invariable air gap between the armature and the pole face. The time intervalmay be very accurately adjusted to the desired value by employing a shim of the correct thickness for the particular time interval desired. The time interval is also adjusted by varying the tension of the spring which biases the armature to the unattracted position, since the time interval is obtained by the pull of the excessive value of flux of the electromagnet overpowering the strain of the spring tending to. move the armature to the unattracted The winding of the electhe time interval of operation of the device;

position. The adjustment obtained by varying the strain of the spring is quite accurate and is simply obtained so that as a practical matter, after a suitable thickness of shim has been determined, the principal adjustment will be by Varying the spring tension.

For a better understanding of the invention, reference is made to the accompanying drawing in which Fig. 1 is a side view of an electromagnetic time element relay in accordance with the invention, Fig. 2 is a front view of the same and Fig. 3 is a very simple diagram of a motor control system, employing the time element relay of Figs. 1 and 2.

Referring first to Figs. 1 and 2, it will be seen that the time element switch or relay comprises an electromagnet structure including the L-shaped frame of magnetic material 10 and the core 11 of magnetic material on which the winding spool 12 is mounted. The framelO and the core 11 are se-' cured in any suitable manner to an insulating supporting base, as for example, by means of the bolt 13. The magnetic movable element or armature 14c of the device is pivotally mounted with respect to the frame 10 and is biased to the unattracted-position by means of the spring 15. This spring is mounted on a bolt 16, which is carried by the support 17 secured to the frame 10. v

The nut 18 is provided for adjusting the tension of the spring 15 and thus varying The shim, 19 of non-magnetic material is secured to the inner face of the armature .1 1-

so as to make abutting engagement with the end of the pole face 11 when the armature is in the attracted position, thus introducing a definite and invariable air gap between the armature and the pole when the armature is in the attracted position and thereby controlling the amount of excess magnetic energy set up and stored in the magnetic structure.

The armature carries acontact 20 at its lower end thereof, and this contact is arranged to make engagement with the stationary and adjustable contact 21.. The. contact 21 is carried by means of a strap of electrical conductingmaterial 22, which. is secured to the insulating support bymeans of the bolt 23. The arrangement is such that a single winding on the electromagnetic device controls the entire 0 eration thereof and this winding has a su cient number of turns so that with the armature in the attracted position the ma netic'fiux of the electromagnet is censidera ly in excess of that required to maintain the armature in the attracted position. When the winding 12 is. short-circuited, the inductive efiect of the electromagnet isemployed to maintain the armature in the attracted position for an apnreciableinterval of time, and'by reason of the fact that the holding flux was considerably in excess of that required to maintain the armature in the attracted position, this time interval will .not be appreciably affected by the variables which affect previous time element devices, namely, variations of the supply circuit potential and variations of the heating of the winding.

Referring to- Fig. 3, the electric motor having an armature 2 1 and series field 25 .is arranged to be connected to the direct current supply circuit by means of the line contactor 27 after the disconnecting switch 26 has been closed. Included in the armature circuit of the motor is the starting resistor 28, the shunting of this resistor being under the control of theresistor contactor 29. The contactor 29 is governed by means of a relay 30 which has theconstruction and mode of operation of the previously described .relay of Figs. 1 and 2. Thewinding of this relay is connected across the supply circuit in series relation with'the resistor 31 after the switch 26 is closed.

- As thus constructed and arranged and withv the various parts in their respective positions indicated in Fig. 3, the operation of the system is as follows When the disconnecting switch 26 is closed, the winding of the relay 30 will be energized across the supply circuit in series relation with the resistor 31. The relay 30 will therefore be energized so as to open its contacts and interrupt the energizing cir cuit of the resistor contactor 29 before this contactor has had an opportunity to close. In order to start the motor, the pilot switch 32 will be closed thereby energizing the line contactor'27 to close, thus connecting the motor to the source of supply with the accelerating resistor 28 included in the motor armature circuit. associated with the line contactor 27 will shunt the winding of the relay 30 so that the closure of this relay will be determined by thelength of time required for the spring- 15 to overpower the holding eflect of the flux persisting in the magnetic structure of the relay while the-winding of the relay is in a short-circuited condition. As before explained this persisting magnetic flux is The auxiliary switch 33 occasioned by reason of the inductance of the relay winding and the time taken by the relay to close will be governed by the length of time required for the current induced by the stored magnetic energy in the relay winding under short circuit conditions to diminish to a predetermined value. The

time interval is also adjustable by adjusting the nut 18 and by adjusting the contact 21 and also by substituting a shim of different thickness for the shim 19 of nb'n-mag- The desired time interval netic .material. delay between'the closing of the line contactor 27 and the closing. of the. resistor contaetor 29 is thus obtained by means of the relay shown more in detail in Figs. 1 and 2.

It will be observed that I have provided a very simple and effective time element relay which depends for its time of operation on the invariable time required for the holding effect of the flux of the relay to diminish when the winding of the relay is shunted. The operation of the relay contact from and to the closed position is entirely under the control of the flux set up by the winding of the relay. The relay is oi itself a very simple, effective and reliable device, and one which can be manufactured in large scale production for a materially lower'cost than other time element. devices with which I am familiar. The provision of the simple, effective and reliable adjusting devices of the relay afford means whereby the time interval may be very accurately adjusted to the exact time desired, and as before stated, this determined time interval will be invariable for all practical purposes.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. An electromagnetic time element device comprisinga magnetic structure including a magnetic movable element biased to the unattracted position, a winding for energizing the magnetic structure to operate the ,magnetic movable element to the attracted position to form in cooperation with said structure a. substantially closed magnetic circuit, said magnetic structure and winding cooperating to set up a magnetic pull on said movable element materially in excess of'the pull required to maintain the movable element in the attracted position against its bias to the unattracted position, a switch contact operated by the movable magnetic element from one position to a second position and from the second position to the first position under thecontrol of the flux set up in said magnetic structure by said winding, and means for controlling the energizing circuit of said winding to cause the excess of magnetic pull set up by said winding and magnetic structure to persist for a time intervalafter operation of said means and thereby provide a delay in the operation of the contact from the second position to the first position corresponding T to the time taken by the excessive magnetic pull on the element to decrease to the value at which the the element. 4

2. An electromagnetic time element device comprising a magnetic structure including a magnetic movable element biased 'to the unattracted position, a winding for energizing the magnetic structure to operate the magnetic movable element to the attracted position to form in cooperation with said strucpull is overcome by the bias of ture a substantially closed magnetic circuit, said magnetic structure and winding cooperating to set up a normal value of flux in said magnetic structure materially in excess of the value required to hold the magnetic movable element in-the attracted position against its bias to the un a'ttracted position,

a switch contact operated by the magnetic movable element from one position to a second position and from the second position to the first position under the control of the flux set up in said magnetic structure by said winding, and means for shunting said winding to cause the excess of flux set up in said magnetic structure by said winding to persist for a time interval after operation of said shunting means and thereby delay operation of said contact from the second position to the firstposition during the time required for the flux in said structure to decrease from the said normal excessive value to the value at which said magnetic member is released for movement in accordance with its bias.

3. An electromagnetic time element device comprising a magnetic structure including a pivotally mounted armature, a spring for biasing the said armature to the unattracted position, a winding for energizing the magnetic structure to operate the armature to the attracted position to form in cooperation with said structure a substantially closed magnetic circuit, a switch contact operated by said armature from a closed position to an openposition and from the open position to the closed position entirely under the control of the flux set up by said winding, said magnetic structure and winding cooperating to set up a normal value of flux in said magnetic structure materially in excess of that required to hold the armature in the attracted position against the strain of said biasing spring, and means for shunting the said winding to cause the excessof flux to persist in said magnetic structure for a time interval after operation of said Winding shunting means and thereby provide a delay in the operation of said contact from the open position to the closed position corresponding to the time required for the flux in said magnetic structure to decrease from the said normal value to the value at which,

said armature is released, and means 'for adjusting the strain of said spring to adjust the value of said time interval.

4L. An electromagnetic time element device comprising a magnetic structure including a magnetic movable element biased .to the unattracted position, a Winding for energ1zing the magnetic structure to operate said magnetic movable element to the attracted position to form in cooperation with said structure a substantially, closed magnetlc circuit, said magnetic structure and winding cooperating to set up a magnetic flux 1n said said structure able element to the attracted position to form magnetic structure materially in excess of the value required to hold the movable element in the attracted position against its bias to the unattracted position, a switch contact operated by said magnetic movable element from one position to a second position and from the second position to the first position under the control of the flux and means for the flux in said magnetic structure below the 'value required to hold said magnetic movable elementagainst its bias with a time delay dependent upon the current induced in said winding due to the decrease of flux in said magnetic structure and thereby delay operation of the contact from the second position to the first position during the time required for the excessive flux to decrease to said value.

5. An electromagnetic time element device having a magnetic structure comprising an L-shaped frame, a core and an armature 'pivotally mounted on the frame'and biased away from the core to the unattracted position, a winding on said core for energizing to operate the magnetic movin cooperation with said structure a substantially closed magnetic circuit, said magnetic structure and winding cooperating to set up a magnetic pull on said armature materially inexcess of the value required to hold'the armature in the attracted position against its bias to the unattr'acted position, a switch contact carried and operated by said armature from one position to a second posltion and from the second position to the first position, and means for shunting said wind ing to decrease the flux in said magnetic structure below said value while inducing a current in the winding for controlling the decrease of flux in said magnetic structure and thereby provide a delay in the operation of the contact from the second position to the first position during the time interval required for the excess magnetic pull on said armature to decrease to the value at which the magnetic element is releasedfor movement in accordance with its bias.

6. An electromagnetlc time elementdevice comprising a magnetic structure including a pivotally mounted armature, a spring for biasing the armature to the unattracted position, a winding for setting up a flux in the magnetic structure to operate the armature to and hold the same in the attracted position, to form in cooperation with said structure a substantially closed magnetic circuit, a switch contact operated by said armature, and means for shunting said energizing winding to release the armature after inducing acurrent in said winding for controlling the decrease of holding flux in said magnetic structure and thereby delay the release of the armature from the attracted osition by the length of time required for t e induced current in the shunted energizing winding to diminish to a predetermined value.

7 An electromagnetic time element device comprising a magnetic structure, an armature having a. knife edge pivotal bearing with respect to said structure, a spring for biasing the armature to the unattracted'position, means for adjusting the strain of said spring, a non-magnetic shim interposed between said armature and the structure to provide a predetermined air gap determined by the thickness of the shim between the armature and-structure when the armature is in the attracted position, a movable switch contact carried by said armature, an adjustable stationary contact cooperating with said movable contact, the said contacts being closed with the said armaturein the unattracted position, a winding for said structure for setting up a magnetic flux in the structure materially in excess of that required to operate the armature to the attracted position and hold the same therein and means for shunting said winding to release said armature after inducing a current in the winding for controlling the decrease of flux in said magnetic structure to the value at which said armature is released and thereby provide a delay in the operation of said contact from the open to theclosed position for a time interval after shunting said winding.

8. An electromagnetic time element device provided with a movable element formed of magnetic material, a magnetic frame, a winding for energizing said frame to operate said element from an unattracted position to an attracted position to form in cooperation with said frame a substantially closed magnetic circuit, means for biasing said element to its unattracted position, said magnetic frame and said winding cooperating to set up a normal value of flux in said circuit many times in excess of the value required to .move said element to said attracted position against its bias to said unattracted position, and a switch contact operated by said element from one position to a second position as said element is movedfrom its unnetic frame to operate the armature to an normal Value of flux many times in excess of that required to move the armature to vice comprising a magnetic frame including said attracted position against the force of "said biasing spring when the winding 1s fully energized so that said flux persists in sald magnetic c1rcu1t for a substantial time interval when said winding is then short cir-' cuited and thereby provides a'delay in the operation of said contact from the open po-' mature is released, and means for controlling-said time interval comprising a non- "magnetic shiminterposed between said armature and said frame for controlling the rate of decav of said flux.

10. An electromagnetic time element dea. pivotally mounted armature, a sprin for blasing said armature to an unattracted position,'a winding for energizing said magnetic frame to operate'the armature to an attracted position to close a magnetic circuit through said frame, and a switch contact operated by saidarmature from a closed position to an open position andfrom an open position to the closed position, said magnetic frame and winding cooperating to produce a normal value of .flux many times in excess of that required to move the armature to said attracted position against the force of said biasing spring when the winding. is

fully energized so that said'flux persists in said magnetic circuit for a substantial time interval whensaid winding is then short circuited and thereby provides a delay in the operation of said contact from the open position to the closed position corresponding to the time requiredforthe flux in said magnetic circuit to decrease from said excessive value to the value at which'said armature is released, and means 'for controlling said time interval comprisinga non-magnetic shim interposed between said armature and said frame'for. controlling the rate of decay of said flux, and means for controlling the bias exerted by saidspring onsaidarmature.

GEORGE B. s'ranua.

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