US1316955A - Leonard p - Google Patents

Description

L. P. HUTT.

CONTACTOR.

APPLICATION mep MAR. 2|. 191s.

Patevll'ted Sept. 23, 1919.

Fig. z.

Figi.

UNITED sTATEs PATENT oEEIcE.

LEONARD P..HUTT, F SCHENECTADY, NEW YORK, .ASSIGNOR T0 GENERAL ELECTRIC I COMPANY, A` CORPORATION v0F NEW YORK.

.GONTACTOR Specification of Letters Patent.

Patented Sept. 23, 1919.

Application mea March 21, 191s. serial No. 223,813.

l subject of the King of Great Britain, residstarting of the motor, therefore,

ing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements 1n Contactors, of which the following isa speci- '.'fication My invention relates to electromagnetic switches for, the control of electric circuits and has for its object the provision of 1mproved means whereby an electricv circuit may be controlled in a reliable, simple and efficient manner.

My invention relates more specifically to electromagnetic switches for controlling electric motor circuits, one ofthe objects being to provide a device of this character which will effect the automatic starting of the motor under the control of the motor current.

In vthe operation of electric motors it is common to both start the motor and control its speed by means of a resistance which is cut in and out of circuit. Everytime a section of resistance is cut out, the current temporarily rises above normal value. The increase in speed which is caused by the cutting out of the section of resistance immediately reduces the current. During the there is a, temporary rush of current for each section of resistance which is cut out. These sec'- tions are frequently cut out of circuit by electromagnetic switches which operate automatically in succession.v In order to prevent the switches from operating too rapidly andV increasing the current beyond a safe value, various means have been devised. An ideal switch for this purpose is onecontaining a winding which carries themotor current and a switch member controlled thereby for cutting out the resistance, the arrangement being suchl that the switch member will not be operated to cut out the resistance until the current has fallen to a predetermined Ivalue and will assume an open position when the winding is denergized. A switch of this character was invented by Walter O. Lum and forms the subject-matter of an application, Serial No.

611,151, led Feb. 27, 1911, assigned to the same assignee as this application.

While the broad features of my device are described and claimed in the said Lum application, the more specific features thereof constitute important improvements which lend themselves to eiliciency of operation and also make the device more accurate and' positive in operation. Likewise, the improved mechanical construction of the switch renders it more rugged and compact and likewise decreases the cost of production.

ing one form of my invention, Figure 1 is cross iece 15 of magnetic material connectv ing t e two branches. The member 13 is between the two members 12 and 14 and spaced therefrom. It is also shorter `than sof the two outside members and provided with a non-magnetic stop 16. forpreventing the switch lever from freezing to the memlber 12. A cross piece 17 of magnetic material connects the outer ends of the two outside members 12 and 14, leaving a space between thel end of the member 12 and cross piece 17 for themovement of the end of the switch lever. Pivoted at 18 -i'n yoke 19 of magnetic material, secured to' or forming partY of the core of the winding 10, is the switch -lever 20. This lever is pivoted intermediate its ends so that the lower end extends downward into the space between the cross piece 17 and the end of the member 13, while the upper end extends upward andfis providedvwlth a contact 2l pivoted at 22 and spring pressed by means of spring 23 to mak contact 24 1n a well understood manner. In

ev a wiping engagement with stationaryits normal position the switch lever 2O assumes the position shown in Fig. 1 in which it rests against a spring pressed plunger 25. The engagement with the spring pressed plunger is made through the screw 26 mounted in bracket 27. The plunger is pressed upward by a spring 28. The plunger slides in an elongated nut 29 which is chambered out to receive the spring 28. This nut is screwed into a lug 30 which is secured to the cross piece 17 by screws 31 and a screw 32 fits into the under side of the lug and holds the spring in place. tension of the spring may be adjusted by turning the screw 32. Copper sleeves 33 encircle the members 12 and 111 to temporarily hold back and prevent the rise of flux in the members as hereinafter explained.

As thus constructed and arranged, the operation of my electromagnetic switch is as follows: Normally the parts are in the position shown in Figs. 1 and 2. iVhen the winding 10 is energized above a predetermined value the lower end of the switch lever will be drawn over by the pull of the magnetic member 13 into engagement with the stop 16. Temporarily the attraction between the member 12 and the switch lever is greater than that between the cross member 17 and the switch lever because of the fact that the magnetic circuit which includes the cross piece 17 is longer than that including the magnetic member 12.Y The copper bands 33 help the members 12 by temporarily holding back the flux so that the lower end of the switch lever will be pulled over by the member 12 and held in the position shown in Fig. 3. In moving to the position shown in Fig. 3, the spring 28 is compressed through the action of the screw 2G and the plunger 27, so that in the position shown in Fig. 3, the spring 28 is under strain. There are now three forces acting on the switch lever. v'iz. the magnetic force at the end ot' member 12 tending to hold the switch lever in open position; second, a magnetic Jforce between the cross piece in the end ot-the switch lever tending to move it to closed position; and a constant mechanical force due to the spring 28 tending to move the switch lever to closed position, lVhen the current in the magnetizing winding 10 is decreased, the two magnetic forces acting upon the switch lever will decrease substantially in proportion, but the force of the spring 28 remains constant. There will, therefore, come a time when the closingforce will overcome the holding-out force and start the switch toward closed position. Vhen the movement of the switch lever toward closed position is started, the movement will be accelerated by the pull of the cross piece 17 due to the shortening of the air gap, and the cross piece 17 will The l finally pull 'the switch lever strongly and cause the contacts 21 and 2-1 to be wiped home in a well understood manner. The value of current in the winding l() at which the switch will operate may be adjusted over a wide range by turning the screw 32.

Vhile I have described my invention as embodied in concrete form and as operating in a speciiic manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto as various modiiications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention the scope of which is set forth in the annexed claims.

That Il claim as new and desire to secure by Letters Patent of the United States, is

1. lern-electromagnetic switch comprising a magnetic structure and a magnetizing winding therefor, a pivoted switch lever normally in open position, a spring and means whereby said lever is moved in an opening direction to place the spring under strain when the` inagnetizing winding is energized by a current above a predetermined 'value and moved to closed position in response to the action of the spring and the attraction of the magnetic structure when the current drops to said value.

2. An electromagnetic switch comprising a magnetic structure and a magnetizing winding therefor, a switch lever pivoted in` termediate its ends and normallyin open position, a spring, and means whereby said lever is moved in an` opening direction by a magnetic attraction on one end of said lever to place the spring under strain when the magnetizing winding is energized by a current above a predetermined value and moved to closed position in response to the action of the spring and the attraction of the magnetic structure on the same end of said lever when the `current drops to said value.

3. An electromagnetic switch comprising a magnetizing winding and a magnetic structure therefor, having two pole pieces, a. switch lever normally in open position and forming a closing gap and a holding-out gap at said pole pieces and a spring cooperating with said lever, said lever being movable by attraction across the holdingout gap to place the springy under strain tending to move the switch lever to closed position when the current in the Winding is above a predetermined value and act with the closing gap-v to move the switch lever to closed position when the current drops to said value.

4. An electromagnetic switch comprising a magnetizing winding and a magnetic structure therefor,having two pole pieces, a pivoted switch lever normally in open position between said pole pieces and forming a closing gap and a holding-out gap at the pole pieces, and a spring arranged to be placed under strain by the movement of said switch lever in response to the attraction across the holding-out gap when the Winding is energized above a predetermined value, said lever being movable to closed lwhen the current drops to position .in response to the action of the spring and the attraction at the closing gap said value.

In Witness whereof 'I have hereunto set my hand this 19th day of March, 1918.

LEONARD P. HUTT.

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