US2428784A

US2428784A - Magnetic motor starting switch

Info

Publication number: US2428784A
Application number: US587809A
Authority: US
Inventors: James D Cole
Original assignee: LAMB ELECTRIC Co
Current assignee: LAMB ELECTRIC Co
Priority date: 1945-04-11
Filing date: 1945-04-11
Publication date: 1947-10-14
Anticipated expiration: 1964-10-14

Description

Oct. 14, 1947. J. D; COLE 2,428,784

MAGNETIC MOTOR STARTING SWITCH Filed April 11, 1945 4 sheetsesheet 1 L Q INVENTOR. JAM ES D. COLE.

Oct. 14, 1947. J. D. COLE 2,423,784

I MAGNETIC MOTOR STARTI NG SWITCH Filed April 11, 1945 4 Sheets-Sheet 2 Oct. 14, 1947. J. D. COLE 2,428,734 MAGNETIC MOTOR STARTING SWITCH Filed April 11, 1945 4 Sheets-Sheet s i I INVENTOR. JAMES D. COLE-.

Oct. 14, 1947. J. D. COLE 2,428,184

YMAGNETIIC uo'fon STARTING SWITCH Filed A ril 11, 1945 4 Sheets-Sheet 4- 'I'IIII'! Id INVENTOR. I JAMES 0,. COLE.

Patented Oct. 14, 1947 'z,42a,1a4

MAGNETIC Moron s'raa'rmc swrrcn James D. Cole, Kent, Ohio, asslgnor to The Lamb Electric Company, Kent, Ohio, a corporation of Ohio Application April 11, 1945, Serial No. 587,809

7 Claims. (Cl. 172-279) "This invention relates to circuit control mechanisms, more particularly circuits for alternat-- ing current motors oi the single phase split phase type.

the circuit actuates the switch mechanism in the.

manner desired.

Another object of the invention is to provide a magnetically controlled switch mechanism in which the parts of the switch mechanism may be delicately and closely adjusted with respect to the strength of the magnetic actuating field, thereby particularly adapting the mechanism for eillcient use over a wide range of frequencies and ratings of motor circuits.

Another object of the invention is to provide a magnetically controlled switch mechanism so constructed as to be free of any gravitational influence, regardless of its position, and in which a quick snap action is provided which prolongs contact life and increases the range and usefulness of the switch mechanism. 7

Another object ofthe invention is to provide a magnetically controlled switch mechanism in which the housing thereof is utilized as a part of the magnetic circuit, resulting in shielding the mechanism from the influence of extraneous magnetizable material.

A further object of the invention is the provision of a resistance swinging armature type of magnetically operated induction motor starting switch which will be free of mechanical vibrations that harmonize with the prevailing frequency of the current in the magnetic coil and which harmonized relationship if not prevented lends to increase the amplitude of the mechanical vibrations of the armature.

Other and further objects of the invention will appear hereinafter when the following specification is read in conjunction with the accompanying drawings, in which Fig. l is a vertical sectional view through the housing of one embodiment of the invention, showing the switch mechanism in side elevation with parts of the magnet winding and conductors broken away;

An object of the invention is to provide mech- I Fig. 2 is a horizontal sectional view through the housing, showing a bottom plan view of the switch mechanism;

Fig. 3 is a vertical sectional view, similar to Fig. 1, but showing switch parts .and magnetic coil in vertical section, parts being broken away to better disclose .the construction;

Fig. 4 is a horizontal sectional view, corresponding substantially to the line 4-4 of Fig. l, and showing the switch contact parts in open position;

Fig. 5 is a view similar to Fig. 4 and showing the switch parts in a dead centered position after beginning closing movement;

Fig. 6 is a view similar to Fig. 4 and showing the switch parts in closed position;

Fig. 7 is a detailed, part elevational, part sectional, view of the adjusting means for varying the pull of the armature biasing spring;

Fig. 8 is a vertical sectional view, corresponding substantially to the line 8-8 of Fig. 7;

Fig. 9 is a diagrammatic view of the electrical circuits illustrating the application of the invention;

Fig. 10 is a vertical sectional view of a different embodiment of the invention;

Fig. 11 is a horizontal sectional view through the housing, showing the switch parts in open Fig. 13 is a view similar to Fig. 11, showing the switch parts in fully closed position;

Fig. 14 is a partly diagrammatic vertical sectional view, disclosing the manner in which the oppositely wound sections of the switch operating magnetic coil are disposed;

Fig. 15 is a reduced sectional view, corresponding substantially to the line l5-I 5 of Fig. 14;

Fig. 16 is a reduced plan view of the housing. with a diagrammatic showing of the circuits; and

Fig. 17 is a reduced side elevational view of the housing, showing the manner in which the conductors are led into the housing.

The conventional type of single-phase induction motor commonly called a split-phase" mowhen operating at full speed, will develop torque and power when current is applied to its main or running winding. It is a well known fact however, that such a motor will develop no torque at standstill unless current is applied simultaneously to the main winding and to an auxiliary or starting winding. It is the purpose of this switching device to close the circuit through the starting winding while the motor is at standstill, and to disconnect the starting winding from the circuit as soon as the motor has attained its approximate full-load speed.

The starting switch under discussion is essentially a relay, so constructed that when the current in the energizing coil reaches a predetermined value, the magnetic attraction between the stationary poles on which the coils are wound, and the pivoted armature, act to close a pair of contacts, permitting current to how through the auxiliary or starting winding of the motor.

It is an inherent characteristic in split-phase motors, that the current taken by the main winding at standstill is much higher, usually 4 to 5 times as great, as is taken by the same winding when running at normal speed. Advantage is taken of this characteristic by connecting the switch energizing coil in series with the main motor winding. When the motor line switch is closed, the relatively high current in this circuit at standstill is sufficient to close the relay contacts, whereupon the motor starting winding becomes energized and the motor immediately comes up to speed. As soon as approximate full load speed is attained and the current in the main motor winding has been reduced to somewhere near its normal value, the relay becomes deenergized to the extent that the contacts are opened, thereby disconnecting the motor starting winding from the circuit.

As shown in the drawings, 20 indicates an oblong base block of insulating material upon which rest the ends of the legs 2| of a U-shaped core member 22, the legs 2| being held in position by screws 23 which extend through the block 29 and into the legs, the parts being located to dispose the member 22 at an angle with respect to the longitudinal center line of the block 20, as shown in Fig. 2. A coil of wire 24 is wound about the bight of the U-shaped core, the broken ends thereof being incorporated in an electrical circuit hereinafter referred to.

Fixedly secured to the block 20, as by riveting, is a post 25, disposed longitudinally in line with the legs 2| of the member 22, the outer end of the post 25 terminating short of the coil 24, and the terminal end provided with a fixed collar 26. Pivotally fulcrumed, midway between its ends, upon the post 25, and inwardly of the collar 25, is an elongated armature bar 21, adapted for cooperation with the coil 24, movement of the bar 21 controlling switch mechanism, indicated genend pivotally mounted upon the post 25, as indi-' cated at 32, the leg 3i bearing against the armature 21, while the leg 30 supports a contact 33 disposed about the post 25 and to which is connected a conductor 34. The outer ends of the legs 30 and 3| are connected by a cross web 35, which carries a contact point 36, adapted in one position to engage a contact point 31 carried by a bracket 39 riveted to the base block 20 and to which is connected a conductor 39.

Inwardly of the web the legs 3| and 32 of the switch member 29 are directed toward each other to form adjacent portions 40 and 4!, between which is pivotally connected, by pivot pin 42, one end of a link 43, the outer end of the link having an arc-shaped opening 44 disposed about the post 25. Connected at one end to the cut out portion of the link 43 is a coiled spring 45, the opposite end of the spring being secured to a pin 46 carried by the adjacent end of the armature bar 21.

The armature bar 21 is normally biased to lie diagonally across the plane of the core member 22, as shown in Figs. 4, 5 and 6, through the medium of a coiled spring 41, one end of which is connected to a pin 48 on the armature bar 21, while the opposite end of the spring 41 is connected to a pin 4'9 eccentrically fixed in the inner face of a member 50, the latter being adjustably supported in a bracket 5! mounted on the base block 20, a stop pin 52 being set in the base block to limit movement of the armature bar 21.

The mechanism described is connected for operation according to the circuit diagram shown in Fig. 9 in which the line wires are indicated at 53 and 54 leading to the main field winding 55 of an induction motor employing a rotor of the squirrel cage type, indicated at 55. A starting winding 51 is interposed in a parallel circuit including the conductor 58 leading from one end of the starting winding 51 to the line wire 53, while the opposite end of the starting coil leads to one pole of the switch mechanism 29, as by conductor 34, the other pole of the switch mechanism 28 through the conductor 39, leading back to the line wire 54, a cut-out switch being shown at 59.

In operation, when the cutout switch 59 is closed, the initial surge of current energizes the main field winding 55 of the motor and simultaneously energizes the coil 24 of the magnet, attracting the armature bar 21, and beginning the closing movement of the switch mechanism 28, which reaching the position shown in Fig. 5, disposes the pivotal points provided by the post 25, the pin 45, and the connection of the link 43 with the armature bar 21, in line in dead-centered position, so that further movement of the armature bar 21 results in a quick snapping action of the parts to the closed position shown in Fig. 6.

The motor then develops adequate starting torque and quickly comes up to speed, whereupon the magnetic flux energizing the coil 24 drops to such an extent that its attraction for the armature bar 21 is overcome through the biasing effect of the spring 41, and reverse action of the switch mechanism 28 takes place, causing a snapping open of the switch contacts and deenergization of the starting winding 51; Under certain load conditions resulting in drop in speed, the increase in the density of the current energizing the coil 24 again results in attraction of the armature 21, closing the switch mechanisms 28 and again cutting in the starting winding 51.

By delicate adjustments, possible through manipulation of an adjusting member 59a, the opening and closing of the switch mechanism 29, and consequent cutting in and out of the starting winding 51, can be precisely regulated over a wide range of varying conditions, and by slightly changing the winding determination of the coil 24 and calibration with the adjusting member We, the invention is applicable over a wide range of fractional horsepower motors. In Fig. lie the adjusting member 50a is shown as having a disk 49!: riveted thereto to cause the hex head of the adjusting member 50a to compress a. spring washer 50c and hold the disk and its spring lug "a in any adjusted position.

In Fig. through Fig. 17, a somewhat different embodiment of the invention is illustrated, the parts of the switch mechanism proper, however, being substantially identical to the parts already described, and accordingly similar reference characters will be employed to designate like parts thereof.

In this embodiment, the magnetic coil arrangement is such that practically all of the outside or extraneous flux influences are eliminated and for that reason is a more advantageous arrangement than the mechanism of Fig. 1. The magnetic means 60 for operating the switch mechanism are connected in series with the main field winding of the motor in the same manner as the coil 24, but are divided into two spaced separately wound sections iii and 62, disposed adjacent to the opposite ends of the armature bar 21 connected in series, as at 63, and acting to attract the opposite ends of the armature bar 21 to operate the switch mechanism as before described. The section 6| of the magnetic means 60 is wound about a core 64 connected directly to one wall 65 of a metallic'housing 6.6 by means of a securing screw 61, while the core 68 for the other section 62 of the magnetic means 60 is connected to the opposite wall of the housing 66 by a securing screw 69, the housing 66 being constructed to enclose the entire switch mechanism, as well as the magnetic means 60. It will be noted in Fig. 14 that the two magnetic coils Gil-6| are wound clockwise whereby the composite flux influence of the two coils is exerted properly upon the armature.

In this form the armature is built up of a composite of sheets of metal of suilicient thinness to permit of the adding to and the subtracting from the mass of the armature to thereby arrive at a total mass which, in the particular mechanical switch actuating environment disclosed, will not have mechanical vibrations that harmonize with the flux frequency of the electro-rnagnets. This purposeful effecting of dis-harmony greatly decreases the tendency of the flux frequency to amplify any mechanical vibrations in the swinging movement of the sensitive armature.

The operation of this construction is identical tothat described in connection with Figs. 1 through 9, the construction having advantages which flow from incorporation of the housing 65 as a part of the magnetic circuit, shielding the entire mechanism from extraneous influences which might tend to disturb the precision adjusted operation of the device. The arrangement of the magnetic means is well adapted for effecting the purpose.

It will be apparent to those skilled in the art that the embodiments herein disclosed accomplish at least the principal object of the invention, and include many advantages some of which are that:

The relay armature, being pivoted at its center, is entirely independent from the influence of the force of gravity, so that the relay can be operated equally well in any position in which it maybe mounted.

In utilizing the relay shell, or cover, as a part of the magnetic circuit, the unit is entirely free from the influence of any outside magnetic material, so that it can be mounted adjacent to, withon or within any iron or steel members, without affecting its operation.

By providing a snap action for the contacts in a magnetically operated switch, the life of the contacts is greatly lengthened and the range and usefulness of the relay greatly extended.

The type of magnetic circuit used in this switch results in a very close relation between the amount of current required to close the contacts and the reduction in current which will permit the contacts to open again. When sufficient current to close the contacts is passed through the coil, then a reduction of only 15 percent in this current value will cause the contacts to open. This close relation between closing and opening current values enables the motor on which this switch is used, to operate satisfactorily over a wide range of voltages.

By the proper coordination between the mass of the pivoted armature and its actuating spring, all vibrational harmonics within the usual alternating current frequency range have been eliminated, so that the switch can be used on any frequency from 25 to 60 cycles inclusive without causing noise or vibration.

By the proper selection of contact material, this switch can be used equally well for the straight split-phase, or for the capacitorstart type of split-phase motor. It also can be used over a. wide range of motor sizes, the proposed unit, while weighing only 4 02., having been applied successfully to all, ratings from ,4 to 1 H. P. inclusive.

I claim:

1. A system of motor control which comprises, in combination, an induction motor, having a circuit including a main winding, and a starting winding; electromagnetic means connected in series with said main winding and energizable by the current traversing said main winding; switch means responsive to said electromagnetic means for controlling energization of said starting winding; and a switch housing adaptable for attachment to the motor frame, said housing having said electromagnetic means connected thereto to cause the housing to form a. magnetic path for said electromagnetic means, thereby shielding said electromagnetic means and said switch means from interference by extraneous magnetic influences from the motor.

2. In a control system for induction type motors, an electromagnetically operated switch mechanism adaptable for closing and opening of the starting winding circuit of the motor including a centrally pivoted magnetically operated armature and a quick make and break switch mechanism operated by oscillation of the armature, coil means and core means energizable through a coil connection with the main winding of the motor for magnetically effecting an oscillatory movement of the armature and the mass of the armature being predetermined to be unresponsive in any of its mechanical vibrations to the frequency vibrations of the field flux of the coil and core means.

3. In a control system for induction type motors, an electromagnetically operated switch mechanism adaptable for closing and opening of the starting winding circuit of the motor including a centrally pivoted magnetically operated armature and a quick make and break switch mechanism operated by oscillation of the arma ture, spaced oppositely wound coils energizable the starting winding circuit of the motor including a centrally pivoted magnetically operated armature and a quick make and break switch mechanism operated by oscillation of the armature, a pair of spaced oppositely wound coils energizable through a connection with the main winding of the motor for magnetically efiecting an oscillatory movement of the armature and the coils being disposed respectively adjacent the ends of the armature and the mass of the armature being predetermined to be unresponsive in any of its mechanical vibrations to the frequency vibrations of the field flux of the coil and core means.

5. In a control system for induction type motors, an electromagnetically operated switch mechanism adaptable for closing and opening of the starting winding circuit of the motor including a centrall ivoted magnetically operated armature and a quick make and break switch mechanism operated by oscillation of the armature, coil means and core means energizable through a connection with the main winding of the motor for magnetically effecting an oscillatory movement of the armature, the mass oi the armature being predetermined to be unresponsive in any or its mechanical vibrations to the irequency vibrations of the field flux of the coil and core means and a metallic housing adaptable for attachment to a motor frame and enclosing the switch mechanism and directly supporting and conductively contacting the core means whereby the armature is shielded from the influence of stray flux from the motor.

6. A system of motor control which comprises, in combination, an induction motor having a circuit including,- a main winding and a starting winding; a switch for controlling the starting winding; magnetic means for controlling said connected with said switch, and a casing support-.

ing said windings and forming a magnetic path from one or said magnetic windings to the other and also forming a closure for said windings and armature; and means for mounting the casing on the motor.

7. A system 01 motor control which comprises, in combination, an induction motor having a circuit including a main winding and a. starting winding; a switch for controlling the starting winding; a metal casing adapted to be attached to said motor, said casing having two opposed walls inter-connected by a third wall; a magnet core projecting from each of said opposed walls; a magnet winding mounted on each of said cores, said magnetic windings being connected in series with one another and in series with the main winding; and an armature disposed intermediate said magnet windings and operatively connected with said switch for actuating the latter, said casing enclosing said armature and switch.

JAMES D. COLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,922,806 Heinrich Aug. 15, 1933 1,991,038 Werner Feb. 12, 1935 1,491,396 Hall Apr. 22, 1924 1,567,598 Jennings Dec. 29, 1925 1,053,340 Ziegler Feb. 18, 1913 1,165,904 Reed Dec. 28, 1915 1,483,962 Wood Feb. 19, 1924 1,533,770 Shaw Apr. 14, 1925 697,273 Plumtree Apr. 8, 1902 1,104,077 Smith July 21, 1914 FOREIGN PATENTS Number Country Date 845,757 France May 22, 1939