US1269278A - Electric switch. - Google Patents

Description

c. T. HENDERSON,

ELECTRIC SWITCH.

APPLHIATION FILED SEPT. 14. 1914.

11,269,278. Patented June 11, 1918.

2 SHEETS--SHEET I C. T. HENDERSON.

mama SWETCH.

APPLICATION FILED SEPT-14. 3914.

1,269,278. 7 intmtui June 1%, 1918.

2 SHEETSSHEEY H W y STATES PATENT OFFICE.

CLARK T. HENDERSON, 0F MELWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER- HAMMER MFG. 00.. OF MILWAUKEE, WISCONSIN, A CORPORATION OF WIS- CON SIN ELECTRIC SWITCH.

Specification of Letters Patent.

Application filed September 14, 1914. Serial No. 861,599.

To all whom it may concern: 7

Be it known that I, CLARK T. HnNnEnsoN, a citizen of the United States, residing at Milwaukee. in the county of Milwaukee and State o ffivisconsin, have invented new and i i111)1()\'11l0flt$ in Electric Switches,

-clithe following is a full, clear, cond'exact description, reference being had to the accompanying drawing, forming a ial't of this specification.

his invention relates to improvements inseries switches. Switches have been de ised called series switches in which a single coil operates the contacts and the magnetic circuit is so formed that the-coil will not close the contacts so long as the current to which it is subjected is above a predetermined value. This magnetic circuit has a portion of restricted magnetic cross-section which becomes saturated when the current in the coil is above a certain limit. A shunt magnetic circuit is provided around the restricted circuit. When the coil is energized with a high current, the excess flux passes through the shunt circuit and acts on a means'which prevents the switch from operating. \Vhen current in the coil de creases, the flux dies out of the shunt circuit, the holding means becomes inactive, and the switch is allowed to operate. The restricted magnetic circuit which'is a necessary element in these switches gives rise to several lin'iitations hereinafter pointed out.

Switches of the above mentioned type are often equipped with contacts which are closed against the pressure of a spring. It is desirable that the moven'ient against the spring pressure be for a considerable -'distance in order lO'COIllPCIlSElli? for wear on 1 the contacts. The force necessary to close thecontacts against the sprlng pressure is larger than that necessary to startthe movement thereof. For this and other reasons it "follows that the force acting on the contacts should be at a maximum value as tl-lecontacts are moved to and held in closed position.

The. restrictions on the magnetic circuit I Iches oi the type described limits the n ma mum closing pull for any given size i switch starts to operate.

- n'iagnetic itcha glVlicn the operating coil and.

the movable parts are made of proper sizefor a given current, the restricted portion of the magnetic circuit must be limited to a proper capacity to insure that the switch will operate when the current decreases to a predetermined value. The capacity of the circuit when so limited i such that it is substantially saturated by the actuating flux passing through it at the time the It therefore cannot accommodate an increase in lines of force and does not act as a return path for the increase in flux. The result is, that as the armature moves to decrease its air gap, the additional flux which would normally tend to thread through the armature and exert an additional pull thereon does not. do so for tne reason that the saturated restricted magnetic circuit does not provide a return path from the armature. Since there is no substantial increase in the amount of flux passing through the armature as it decreases its air gap, the pull does not increase to the high nuiXimum dcsirable during final closing movement. Curve A in Fig. 4 illustrates the change in pull on the armature as the air gap decreases in a given size of switch having a restricted circuit. This curve shows a slight rising pull as the air gap first decreases but the curve drops away and becomes almost horizontal as the air gap becomes small indicating that no substantial movement of the armature.

The restricted magnetic circuit thus limits the maximum closing pull obtainable in a given size of switch. An increase in pull on a given size of contacts obtained by increasing the size of the coil, thearmature and the magnetic circuit, or either of them, above what would otherwise be neces sary to secure operation. on predetermined current, is objectionable for several reasons among which are that the switch is more expensive and an increased space for installation is necessary.

One of the objects of the present invention is to provide a magnet with means for increasing the pull on its armature after the armature has responded.

provide a magnetic structure in which the armature is actuated to and held in. closed position in a positive and forceful manner.

Another object of the invention is to provide a switch in which the contacts will be firmly forced to and held in closed position regardless of limitations in the amount of flux available to start the switch.

Another object of the invention is to provide an electromagnetic structure in which an additional path is provided for the flux after the movement of thearmature has been initiated.

Still another object of the invention is to provide means for completing an additional magnetic circuit for the flux having a restricted magnetic circuit to thereby increase the pull on the armature as the switch closes.

Various other objects" and advantages of my invention will hereinafter appear.

The accompanying drawings illustrate an embodiment of my invention and in said drawings Figure 1 is a side elevation of the switchembodying one of the preferred forms of my invention.

Fig. 2 is a partial side elevation of a modified form.

Fig. 3 is a cross section of themodification shown in Fig. 2.

Fig. a represents the pull curve diagram explained in detail hereinafter.

Fig. 5 is a side elevation of another modification of, the invention. I

Figs. 6 and 7 are apartial side elevation and an. end view of a modification of thestructure shown in Fig. 5. 7

Figs. 8. and 9 are a partial side elevation and an end View of still another modification of the structure shown in Fig. 5. The switch comprises in general a stationary contact 3, a cooperating movable contact 4, amain switch frame carrying an operating coil 5 and amovable armature 6 upon which thecontact 4 is mounted.

The switch frame, which also acts as a magnetic circuit, has a top 7 of brass or other non-magnetic material, a bottom Sof magnetic material and a side member 9 also of magnetic material. The :side 9 is of limited magnetic cross section. It. acts as a magnetic throttle in a manner hereinafter described. 7

The non-magnetic top -7 of the frame causes, substantially all the flux from the magnetic core 10 of coil 5 to normally pass across an air gap 15 to armature 6. a The normal return path for this flux is through armature 6, magnetic support 1 1, magnetic This circuit is side member 9 to bottom .8.

of limited capacity since the-part -9 is of naeaere 17. The movable armature structure is bal-'.

anced to normally rest in the position shown in Fig. 1 with the bar 16 in engagement with the brass adjusting screw 18. The screw 18 regulates the length of air gap 19v be: tween bar 16 and pole piece 17 The shunt magnetic circuit may be traced from core 10 through arn'iature 6, bar 16, pole piece17, member 8 to core 10.

The movable contact 1 which is supported by the armature 6 may be of any suitable type. It is shown in this instance as pivoted to the armature by means of a bracket 12 and pivot 13. The bracket 12 is biased forward by a spring lil: so that the contacts 4; and 3' engage before the armature 6 seals with the. core 10.- The contact 4. is thereby given a sufficient movement against spring .pressure after engagement to produce a wiping action.

When the coil 5 is energized with a high current, the member 9 becomes saturated and the pull at gap 19 is'weahened because a greater proportion of the flux is carried by the mei'nber 9. When the current reaches a predeterminedvalue. the pull at gap 15 overcomes that at 19 and the switch is closed.

Fig. 1 illustrates one form of means for securing a high maximum. pull on the armature. This means increases the pull in a given size of switch without materially effecting its predetermined current operating cl1aracteristics The means may be embodied in a variety of forms. It comprises in general a means for completing an additional path for the liuxafter the armature 6 has started in its movcmenttoward core 10.

An extension 20 of magnetic material projects outwardly from the switch frame below the bar 16. This extension is curved approximately concentric with the are described by the end of bar 16 and terminates in a head :21 which is engaged by the bar 16 when it reaches the dotted line position shown in Fig. 1. An additional path is thereby provided for the flux, which path constitutes the armature 6, bar 16, head :21 extension 20 and member 8. This Path becomes active as soon as the bar 16 approaches close enough to the head 21 to enable the flux to bridge the gap between said members. The additional path constitutes a goocl.return'c1rcu1t from the, armature for the increase in flux through the same as it approaches its core, and the pull on the armature is thereby greatly increased. A suppleinental pull is also exerted by head 21 on bar 16.

The operation of the switch shown in Fig. 1 is as tollows,when the coil 5 is energized, by high current, the flux saturates the part 9, and the excess flux follows a path through bar 16 and gap 19. The pull at gap 19 on bar 16 is more effective than the pull at gap 13 on armature 6. The switch is consequently held open. As the current in coil 5 decreases the. flux decreases until the greater proportion of it is carried by the member 9. The pull across gap 19 is thereby weakened and when the current reaches a certain value the pull at gap 15 overcomes. that at gap 19 to close the switch. The movement of the armature 6 toward its core throws bar 16 away from its pole piece 17, thereby opening the magnetic circuit through bar 16 and pole piece 17.

Further movement of the armature 6 causes the bar 16 to approach and engagethe head 21. An additional magnetic circuit is thereby completed for the flux through the armature 6. The flux may accordingly increase through the armature 6 and exert an addi tional pull thereon to sealit with the core in a firm, positive manner. The pull on bar 16 through head 21 supplements the pull of main armature 6.

Curve B in Fig. 4 of the drawings shows the manner in which the pull increases the air gap decreases in a switch provided with an additional path such as above set forth. This curve may be compared with curve A representing the pull in a switch of the same size and type without the additional magnetic circuit. It will be noted that the pull on the armature when the air gap is small and as the armature seals with its core is much larger in curve B where the switch is equipped with an additional. flux path.

Figs. 2 and 3 illustrate a modification of the extension 20 as applied to a switch of the type shown. The head 21' of the extension 20 in the modification has two side members extending therefrom toward the pole piece 17 to form a channeblike member for receiving the bar 16. The space between the members made to accommo-' date the bar 16 with the smallest clearance possible consistent with good mechanical operation. lVhen the bar 16 enters the space between members 23, a'magnetic circuit is completed through the bar across the small air gap to members 23 and back through the extension 20 to member 8 and the i'nagnet core. An additional path for the flux is thus provided before the armature 6 has completed its movement. This additional path causes the pull on the armature an additional side member 26 terminating in a sloped-oft end 27. ,The armature 6 is extended and provided with a head 28 which is beveled to lit the end 27 of the side member 26 when the armature 6 seals with its core. The shape of the part 27 and the cooperating head 28 may be varied to suit different conditions, but the structure shown is found very desirable because the reluctance of the circuit decreases very rapidly as the head 28 moves toward the part 27. lVhen the armature 6 moves toward its core, an additional magnetic circuit is completed through the armature extension 28 and the side member 26. This circuit becomes active before. the part 28 actually seals with the part 2? since the reluctance of the circuit is rapidly decreased as the air gap 29 is decreased. The length oi the air gap 29, when the switch is open. should be so adjusted that the predetermined current operating characteristics of the switch will not be materially affected. -The other parts of the switch are. of the same structure as illustrated and described in Fig. '1 and the operation of the switch is in general the same.

Figs. 6 and '4" illustrate a modification of the structure shown in Fig. The upper end of the side 26 of the frame in this modification. has two members 32 extending upwardly therefrom. The armature 6 is provided'with' an extension 31 which moves be tween the parts 32 and completes a magnetic circuit from the armature 6, through the extension 31 to the side members and. This cir-- through the part 26 to the core. cuit is completed before the armature 6 has reached the limit of its movement and. an additional nia netic circuit thus provided at an earlier period in the movement of the armature than in the structure shown in Fig. The arms 32 may be made in various lengths to vary the point at which the additional magnetic circuit isgcomplcted in the movement of the armature.

Figs. 8 ant 9 illustrate another modification of the structure shown in Fig. 5. The side is provided with a tapered end 3'5 which cotiperatcs with an opening 37 in an extension 36 of the armature 6. 36 moves over the end 35 and completes an additional magnetic. circuit tln'ough the part 36 member 35 and the side 26 to the core.

lvhile I have shown and The extension" described a preobvious that many changes may be made in the details of construction and arrangement of parts without departing from'the spirit v and scopeof the appended claims.

Having desc'ribedmy invention, what I claim and desire to secure by Letters Patent 1. An electromagnetic mechanism cornprising an electromagnet, a movable armature, and means including a magnetic cirbuit of limited capacity and an extension .of said armature for magnetically preventing movement of the armature when current in the magnet winding is high, said mechanism having a member for reversing the magnetic pull on said armature extension after it has responded.

2. An electrdmagnetic mechanism having amovable armature, an operating windin therefor, and means including a magnetic circuit of limited capacity for preventing movement of the movable armature when .the Winding is initially energized above a --a,- member with which the movable armature cooperates upon the movement thereof to (complete a magnetic circuit in shunt to the .-circ uit of limited capacity for increasing the pull on the movable armature after movement thereof has been initiates.

.3. An electromagnetic mechanism having "a movable armature, an operating winding,

means by'which said winding eXterts a pull to move said armature and an opposite pull 3510 .hold the armature against movement when the initial current in. the winding above a predetermined value, and a member associated with said mechanism and rendered active upon movement of the m'ovable armature for causing some. of the hold- Zing Qux to assist in moving the armature after the moving pull has overcome the hold ing pull. I

4. A magnetic mechanism having a movable armature, a main magnetic circuit havmg a portion of limited capacity, a magnetic circuit in shunt to said portion of the main circuit of limited capacity, the shunt circuit including a portion of the movable armature. and a member associated with said mechanism by which said portion of the movable armature completes a second magnetic circuit in shunt to the limited capacity circuit during movement thereof to increase the capacity of the main circuit to thereby increase the pullon the movable armature during movement thereof.

. 5. An electromagnetic mechanism having a movable armature, an operating winding therefor, a magnetic circuit of limited capacity, means controlled by excess-flux for predetermined value, said mechanism havingv estates the armature after movement thereof has been initiated.

6. An electromagnetlc mechanism having an operating winding, a movable armature,

a main magnetic circuit including said armature, said circuit having a portion of limited magnetic capacity, said armature having a portion normally forming a magnetic shunt to the portion of the main magnetic circuit oflimited capacity and said mechanism having a member by which said portion of the armature completes another shunt magnetic circuit to the portion of the main magnetic circuit of limited capacity as the armature is moved to closed position.

7-. switch having a movable armature adapted to control the switch contacts. an operating winding therefor, means by which said Winding: is caused to extort an actuatinc; force in one direction on one part of said armature and a holding force on another cart of said armature. and a member associated with said switch for causing some of the holding flux to be reverse in direction of operation during movement of the armature so that it assists the actuating force after the armature has started to move.

8. A switch having; a single winding for operating its contacts, a magnetic circuit of limited capacity for the flux from the windinej. means controlled by excess flux from said circuit to prevent closure of the switch when the initial current in. the winding eX- coeds a predetermined value, and a member 190 associated with said switch for completing an additional path for the excess flux through.- said means as the switch closes so that a high pull will be exerted on the switch during closing movement thereof.

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