USRE24308E - Motor speed controller - Google Patents

Description

April 23, 1957 N. E. coL-EGROVE Re- 24,308

' Mo'roRf sPEE coNTRoLLR Orgingl Filed Oct. l2, 1948 v United States Patent VOilice Re. 24,308 Reissued Apr. 23, 1957 White Sewing Machine Corporation, Cleveland, Ohio,

a corporation of Delaware Original No. 2,631,265, dated March 10, 1953, Serial No. 54,124, October 12, 1948. Application for reissue July 3, 1956, Serial No. 595,808

17 Claims. (Cl. S18- 346) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to a speed controller or regulator for an electric motor and, more particularly, to an improved device for controlling the energization of an electric motor in a manner to enable the latter to be operated at any desired speed within a continuous range extending from zero to and including the maximum speed at which the motor is designed to operate.

One commonly employed mode of controlling the speeds of electric motors is to utilize control elements which vary the voltage input to the motor. This type of speed regulator or controller has the disadvantage that the motor, when operating at low speed, is energized at relatively low voltage and, hence, the motor at such low speeds does not develop its maximum power. In the operation of certain apparatuses or devices at low speed it is desirable and requisite for the motor driving the apparatus or device to develop its maximum power at low speed if the apparatus or device is to function at full eiciency. In fact, many devices or apparatuses require greater power for etlicient operation at low speeds than they do when operating at high speeds, since, in the latter case, the momentum of the parts facilitates the operation of the apparatuses or devices. An excellent illustration of the advantage of an electric motor developing full power at low speed is found in connection with the electric drive motor for a sewing machine. For example, the operator of a sewing machine often desires to run that machine at low speed and this situation frequently exists when the sewing is being performed on relatively thick-materials or upon a number of layers of material, so that maximum power is required to pass the needle of the machine through the material. When the electric drive motor of the sewing machine is controlled by a speed regulator or controller of the type which carries the voltage input to the motor, the latter will not develop its full power at low speeds and hence the machine does not function eiciently at such speeds since, as noted above, the low speed operation of the machine is generally at a time when maximum power is required. While a sewing machine motor has been mentioned by way of illustration, it will be apparent that a similar problem arises in connection with drive motors for apparatuses or devices of other types and, hence, reference to sewing machine motors is merely illustrative and is not to be construed as a limitation.

An object of this invention is, therefore, to provide a speed regulator or controller for an electric motor such that the motor is energized for rotation at any desired speed at full line voltage, so that the motor has substantially the same power at all speeds.

Electrical motors have also had their speeds controlled or regulated by centrifugal governor type devices. Such controllers or regulators depend for operation upon the acceleration or deceleration of the motor controlled and, hence, are subject to inertia and other effects which minimize their accuracy and eiciency.

Another object of this invention is, therefore, to provid a speed regulator or controller for an electric motor which is accurate and eiiicient, does not depend for operation upon acceleration or deceleration of the motor, is relatively inexpensive to construct and which may be readily employed with conventional motors without altering their construction, since the motor windings are not employed to aid in effecting the speed controlling function.

A more specific object of the invention is to provide a speed controller or regulator Vfor an electric motor such that an impedance in the device is in series with the energizing circuit of the motor and is periodically shortcircuited so that the motor is energized by impulses of electrical power at full line voltage, the speed of the motor being controlled by variation of the duration of the impulses under the control of the operator, maximum speed of the motor being achieved when the interval between the impulses becomes zero; that is, when the impedance is continuously short-circuited.

A still more specic object of the invention is to provide a speed controller or regulator for an electric motor of the type dened in the preceding object and in which the said impedance is the coil of an electromagnet, the armature of which vibratesl one contact relative to a second contact with the said contacts being connected in parallel with the coil of the electro-magnet so as to short-circuit the latter when the contacts engage, the second-mentioned contact being adjustable to vary the duration of the engagement of the contacts thereby selecting the speed of the motor.

Another object of the invention is to provide an improved speed controller or regulator for an electric motor as defined in the preceding object and in which the means for adjusting the adjustable contact cooperates with the latter to provide an off-on switch'for the motor which is controlled.

The invention further resides in certain novel features of construction and combination and arrangements of parts, and further objects and advantages thereof will be apparent to those skilled in the art to which it pertains from the following description of the present preferred embodiment thereof described with reference to the accompanying drawing, in which similar reference characters represent corresponding parts in the several views, and in which:

Fig. 1 is a side elevational view of a circuit controller or regulator constructed in accordance with this invention, portions of certain parts being broken away to more clearly reveal the construction;

Fig. 2 is a bottom view of the controller or regulator illustrated in Fig. 1;

Fig. 3 is an end elevational view of the controller or regulator illustrated in Figs. 1 and 2, showing the left-hand end of the controller as viewed in those figures;

Fig. 4 is a detached plan view, on a reduced scale, of a sub-assembly of the illustrated controller or regulator comprising the armature, the vibrating contact, and the vibration damping member; and

Fig. 5 is a schematic wiring diagram of the circuit of the controller or regulator as applied to a motor for controlling the speed of the latter.

As shown in the drawing, the present preferred e'mbodiment of the motor speed controller or regulator com` prises a mounting plate 10, which is preferably formed of insulating material, and provides a convenient means t0 mount the device. Mounted upon the plate 10 is a substantially U-shaped member 11, formed of magnetically permeable material; such as iron or the like. This member has its ends 12 and 13 bent outwardly at substantially right angles with respect to its legs andthe end portion 12 engages'the mounting plate 10 so that the member 11 extends at substantially right angles with respect to the plate The member -11 -is-securedto the plate 10v by a machine screw, or the like, 14 which passes through the plate 10 and has its inner end threadably received in a tapped opening in the adjacent leg of the U-shaped member 11, a bushing 15 being provided about the screw 14 intermediate the mem-ber 11 and the plate 10.

The lower surface of Vthe end portion 12 of the U- shaped -member -11 serves as a mounting support for a movable armature and contact assembly. As shown in the drawing, this assembly comprisesa resilient, elongated amature mem'ber 16, which `is preferably a leaf spring formed of magnetically permeable material; a resilient contact carrying member 171; an insulating bushing or plate 18; a exible contact carrying arm cr member 19;- anda second insulating bushing or plate 20.. This assembly is preferably mounted and secured together by mounting screws 21 in the manner shown in Fig. 1, from which it will be seen that the mounting screws pass through aligned open-ings lin the insulated plate 20, ilex- .4

ible contact arm or member 19.1, insulating plate 18, and resilient member 16 in that order, the inner ends of the mounting screws being threaded `into tapped openings in the portion 12 ofA the U-shaped member. It will be observed that the openings in member 1'9 for the mounting screws are of considerably larger diameter than the latter toy provide for insulation between this member and the` screws. As. illustrated, this insulation is effected by bosses onA the insulating member 20- which surround the screws and extend, with a clearance, through the openings in the member 19,. It will of course be appreciated that instead ofemploying such integral bosses, the desired insulation may be effected by separate sleeves. or bushings of insulating material. The rear portion of the armature member 16 is secured to. the enlarged rear portion 17a ofthe member 17 by rivets or the like 22 so that the amature forms a part of the assembly supported by the screws 21. It is evident that the members 11 and 17 are in electrical conductive contact while the arm 19 is electrically insulated from both th-e members 11 and 17.

Inthe; present preferred' embodiment the armature member 16. is shown, see Fig. 4, yas comprising a platelike leaf Aspring of magnetically `permeable material having a substantial-ly rectangular coniiguation and provided with `a cutout portion or opening, which is, substantially rectangular adjacent the free end, of the member and tapers towards the other end of the member Which is preferably closed'. TheV innerI closed end of the armature 16 -is preferably provided with a notch or recess 16a the. dimensions of which Iare selected so as. to. provide I'the desired degree of flexibility of the membet The contact carry-ing member 11 has, as previously stated, an enlarged rear portion, designated 17a which is substantially rectangular and is provided with openings for the mounting screws 21 and for the rivets 22 which secure the members 16 and 17 together. A-,s shown` in Fig. 4, the ,Contact carrying portion of the member 17 is elongated and is. of lesser width than the member 16 thus providing a tongue-like portion extending substantially centrally of the width `of tapered portion of the central opening in the armature member 16 and terminating an appreciable distance from the outer edge of the opening. Secured .to the member 17 adjacent its outer free end is an electrical contact 23.

While the member 16 andr the contact. arm `0r member 17 have been, shown and described as two separate pieces of material which are secured together, it will be apparent that they may be formed from a single piece of spring-like material, the portions of the central area of which have been removedl yto provide a tongue-like contact carrying portion intermediate the sides of the opening. Moreover, it is not essential that the inner end of the amature member 16 be closed as shown nor that the sides of the member adjacent the central opening taper as shown. Furthermore, `it is not necessary 4. that the members 16 and 17 be resilient through their entire lengths, but maybe formed of relatively rigid material having integral or separate portions of sufficient ilexibility to permit vibration of the members.

The leg 24 of the U-shaped member 11 forms, a support for an electromagnet 25 which is so mounted thereon that the leg 24 and its -end portion 13 cooperate with the core of the-.electromagnet to form one pole piece for the latter. Preferably,A the leg 24 and .the portion 13 of the U-shaped member extend through the rectangular portion of the openingl in the armature member 16, as shown in Figs. l and 2, so. that the armature 16 surrounds the leg 24 adjacent its lower end. The electromagnet 25 is provided with a second pole piece 26, which has f its lower or free end 27 bent inwardly toward the `adjacent end portion 1 3 of the U-shaped member 11, the end portion 27 being a greater distance from the electromagnet than the portion 13 so that; the field extending between the ends of the pole pieces, when the electromagnet is energized, is so directed as to have a maximum effect in attracting the armature 16, which due to its cantilever-type mounting tends to move in an arc. The movement of the armature in response to energizaticn of the .electromagnet causes the member 17 to iieX, since these. members` are secured together, and the resiliency of the members returns them to ltheir initial positions, substantially as shown in Fig. l, when the electromagnet is deenergized.

Secured to the armature member 16 adjacent its outer free end is a member 28 which is preferably rectangular and \has a substantially rectangular central opening substantially aligned with the corresponding portion of the opening in the member 16 so as to likewise surround the leg` 24 of the electromagnet adjacent its lower end. This member 28 is. formed from an electrically-conductive, non-magnetic material, for example zinc or the like, and hence forms, in effect, a single turn, closed circuit, low resistance path for currents of electricity induced therein by changes` in the magnetic flux in the leg 24 as the electromagnet is repeatedly energized and deenergized as hereinafter described. As is, well known, the currents induced inV the member 2S are such as to oppose the movement .of the latter and hence of the members 16 and 17 thereby damping the movements of these members in response to. energization and deenergization of the electromagnet. This prevents the spring-like armature member 16 and the contact member 17 from reaching their natural frequency of vibration, it being understood that frequency of their vibration is also governed by the dimensions of these members, of the previous mentioned slot or recess 16a, `and by the size of the coil of the electromagnet. The dimensions and characteristics of the parts are preferably so selected that the frequency of vibration of the armature 16y and member 17 is different from that of the periodicity of the electrical energizetion of the electromagnet 2,5. By way of example, devices constructed as shown and described have been found to have a frequency of vibration of the armature 16 and contact member 17 in the order of 6,00 to 900 vibrations per minute vwhen the electromagnet was energized with 60 cycle alternating current, the frequency of vibration being readily controlled by suitable selection of the size of the coil of the electromagnet, the size and weight of the member 28 and/or the size and resiliency of the members 1,6 and 17.

Preferably the portion 27 of the pole piece 26 is provided with a stop or bumper 29, which may be formed of rubber, leather, or the like, and is adapted to be engaged by the member 28 and thereby limit the travel of the latter and of the members 16 and 17.

The electrical contact surface 23 on the member 17 is adapted to engage a contact surface or portion 30 Carried by the outer end of the `arm or member 19, as hereinafter described. In order to control the duration of this engagement, the arm or member 19, intermediate its point of mounting and its contact 30, is provided with a cam-shaped portion or surface 31 which, in the instant case, lis shown as comprising a somewhat V- shaped bend in the member. This cam-shaped portion of the member 19 is adapted to be engaged and moved by a cooperating cam surface under the control of the operator, thereby varying the separation between the contacts 23 and 30 when the latter are in their normal posit-ions and, hence, varying the duration of their engagement when the contact 23 is vibrated by operation of the electromagnet 25. The operator controlled cam surface is, in the present instance, provided by a somewhat conically-shaped member 32 integral with, or secured to, the outer end of a push -rod 33 which is slidably supported in a cylindrical guide 34 passing through an opening in the mounting plate 10, the guide 34 being secured to the mounting plate in any desired manner.

The rod 33 extends beyond the guide 34 and is adapted to be actuated by the operator of the device by the latter pushing inwardly thereon. This may be effected in any desired manner but, when the device is to be employed with a sewing machine or the like, it is convenient to provide an actuating member or lever for cooperation with the outer end of the rod 33 and which may be operated by the knee, foot, or hand of the operator. Consequently, when reference is made hereinafter and in the subjoined claims to manual operation of this member, it is to be construed as covering actuation by the operator Whether by the hand, arm, foot, leg or other part of the body. Since actuating members of the type just mentioned are well known and widely employed for similar actuation when used with other types of controls, lsuch a member or means is not here illustrated.

The rod 33 interiorly of the guide 34 is provided with a collar or cylindrical ange 35 which provides an abutment for one end of a compression spring 36, the other end of which abuts against the inturned edge of the adjacent `end of the guide 34 so that the conically-shaped member 32 is normally retained in its retracted position, as shown in Fig. 1, but may be moved forwardly therefrom by a thrust exerted upon the outer end of the rod 33. Adjacent the rear end of the conically-shaped member 32, the guide 34 is provided with a washer or collar 37, which is preferably formed of insulating material and is adapted to engage the under surface of the member 19 so that the cam-shaped surface 31 of that member is prevented from engaging the member 32 when the latter is in its retracted position, see Fig. l.

One lead 38 of the electromagnet 25 is preferably connected to the U-shaped member 11 and the latter is provided with a terminal member 39 projecting outwardly, that is, to the right of the supporting plate 10, a bushing such as 40 surrounding the portion of this terminal member intermediate the member 11 and the plate 10 so that the terminal and bushing also assist in properly positioning and supporting the member 11 upon the plate 10. The other lead 41 of the electromagnet 25 is electrically connected to the member 19 as by soldering, or the like.

An electrical condenser 42 is supported by the substantially horizontal portion of the U-shaped member 11. This condenser has one terminal 43 electrically connected with the member 11 and the other terminal connected by a lead wire 44 to the member 19. The guide member 34 constitutes a second terminal for the regulator and is conductively associated with the member 32 in the preferred embodiment by virtue of the member 32, rod 33 and guide 34 all being constructed of metal. It will be apparent, however, that the rod 33 may be formed of conductive material other than metal or of insulating material, if desired, and if insulating material be used the guide 34 and member 32 may be electrically connected by a exible lead or other expedient.

In employing the :speed controller or regulatorof this invention, the motor M, whose speed is to be controlled,

has one lead 45 thereof connected with a power supply line L1. The other lead 46 of the motor is then connected to the terminal 39 of the controller and the power supply line L2 is connected with the guide member 34 of the controller. With the parts of the controller in their positions as shown in the drawing, which corresponds to the non-operating position of the controller and of the motor, the circuit to the motor is interrupted and the electromagnet 25 is not energized.

When it is desired to operate the motor, the operator pushes inwardly on the rod 33. This moves the conicallyshaped member 32 to the left, as viewed in Fig. 1, engaging it with the cam-shaped ysurface 31 of the member 19. The initial engagement of the member 32 and the portion 31 completes a circuit from one side of the power supply through L2, guide 34, rod 33, members 32 and 19, and lead 41 to the electromagnet/ZS. This circuit is completed from the other lead 38 of the electromagnet [through member 11,] and terminal 39 to the motor lead 46, thence through the motor windings and the lead 45 to the other power supply line L1. Consequently, the electromagnet 25 is energized so that the armature 16 and contact carrying member 17 are attracted towards the portions 13 and 27 of the pole pieces.

When the power supply employed for the motor M is of the alternating current type, the cyclic reversals of the current cause the armature 16 and the contact arm 17 to be rapidly repeatedly vibrated. Therefore, the

contact 23 carried by the member 17 is rapidly periodically moved towards and away from the contact 30. The separation between these contacts at the time of initial engagement of the conical members 32 with the cam surface 31 is preferably such that the vibratory movement of the contact 23 does not have sufficient amplitude to effect engagement of that contact with the contact 30. The impedance of the winding of the electromagnet 24 is preferably such that the voltage drop therethrough, when the impedance is in series with the motor M, is such that the latter does not operate. If the operator pushes further upon the rod 33, however, the conical member 32 now in engagement with the cam portion 31 of the member 19 moves the latter and its contact 30 further in the direction of the contact 23. When low speed operation of the motor is desired, the movement of the rod 33 is such that the member 19 is positioned so that the contacts 23 and 30 are engaged during each vibration of the armature 16 for an interval of veryl short duration.

The engagement of the contacts 23 and 30 short-circuits the coil of the -electromagnet 25 so that during the time the contacts 23 and 30 are in engagement, the motor M is Isupplied with an impulse of electrical power lat full line voltage, the circuit lthen extending from L2 through the members 34, 33, 32, 19, ycontacts 30, 23, and the member 1!1 to the terminal 39, thence to and through the motor land to the power supply line L1. The frequency of these impulses of full line voltage is `of course the same as the frequency of vibnation 0f the armature 16 which is selected, as above described, by suitable selection of the dimensions and characteristics of the various elements of the device. Consequently, the motor M -is operated at :a speed depend-ing upon the duration of the intervals when the contacts 23 Iand 30 momentarily touch during each vibration. The selec-ted speed may be extremely low but the motor is, nevertheless, operated at substantially its full power due to the rapidity of the impulses, which may be in the order of from 600 to 900 per minute, and the fact that ythey are at full line voltage. When higher speeds are desired, the rod 33 is positioned further to the left as viewed in Figs. l and 2, so that the duration of engagement of the contacts 23 and 30, during each vibration of the for-mer, is lengthened with the result that the motor M receives full li-ne Voltage impulses of correspondingly longer duration and hence operates at higher speeds.

The controller is so constructed that the rod 33 may be moved far. ,enough so that. the contacts 23. and 3|).y are. vin continuous-'engagement and, consequently, the motor M is: then operatcdat full. speed and' at full line voltage, since the impedance; of lthe electromagnet 25 is continuously short-circuited. The speeds of the motor m-ay be readily varied from zero to maximum by simply actuating the rod 331 and a-tV all. speeds the motor is energized by impulses of `full line voltage so that it opera es Iat substantially its full power regardlesscf'rthe selected speed.

When pressure isl removed from the rod 33, the spring 3.6' -IEQiurns the latter to the position shown in Figs. 'i and 2. so that. the member 19. rests upon the Washer or colla-r 375 thereby linterrupt-ing the engagement bet-Ween the cam surface. 31 andthe conically-shapedY member 3x2 with the ITQSJllLt that the circuit. 'to the electromagn-ct and the motor is. broken. It is eviden-t, therefore, that the circuit controller also. provi-des an oft-on switch, as well as etlectingselection of the speed of themotor.

It. will be observed.' that the; circuit controller ot this invention issuch that, while the motor M is energized by rapid impulses of electrical power at full line voltage, the circuit 't0 the,y motor is not com letcly opened when the contacts 23 and 30 separate since the impedance of the el-ect-romag-net remains in the circuit in series with the mot-or. This greatly reduces sparking between the contacts 2 3.V and 30, and the. condenser 40, which is bridged acrossthe contacts, further reduces or entirely eliminates any sparking; at the contacts 23 and 3i), thereby reducing or substantially eliminating radio disturbance and lengthening the life of the contac-ts. lfdesired, this condenser may omitted without altering the operation of the device except for a possible slight sparking at the contacts.

While they circuit .controller of this invention has been particularly described with respect to its use -in conjunction withalternating current, `it will be apparent that the dcvice is n-ot limited to use with electrical power of that type` but may be readily employed with direct current. Thisis duetov the fact that, when the contacts 2G and 30 'are in engagement, thev coil of the electromagnet 25 is short-ci-rouri-.ted,l and hence the armature 16 would be rez turned. t-o its upper position by the resiliency thereof Whether ythe device is employed with direct or alternating current and nosepa-rate make-and-bre-ak is neces-sary for use withk direct current.

Furthermore, the impedance in series with the motor need not be the coil of the electromagnet but may be a separa-te element .across which the contacts 23. and 3!) are bridged, the electromagnet then being utilized solely to operate. the. contacts. Moreover, the impedance in such cases maybe anon-inductive resistance.

Hence,` the termv impedance as used through the description and. claims of; this application is employed, and is intended tobe construed, in its generic sense to include both-resistance plus inductance or simply a non-inductive resistance since it is obvious that the equation for an inductive circuit:

when w=0, i. e., the electromotive force is not varying, (2r-when L.=0, i. e., the. circuit is non-inductive (see page 236,01. Gilbert,` Electricity and Magnetism, 1932 edition).

It will bereadily understood that the novel circuit controlleror regulator may be provided. with a suitable housing or. casing, which has not here been illustrated forv the purpose of simpl-itication land to more clearly show the operating: features of. the mechanism. Likewise, various detailsof theconstruction may be modified or altered by one sklljefd.- in. thewart after. having: had the advantage of thisv disclosure without departing from the spirit of4 the 8 invention and,v consequently, the detailed description and illustration should be understood as illustrative only of lthe present preferred embodiment of the device and not as a limitationjupen the invent-ion.

Having thus described my invention, I claim:

l. A speed. control-ler for an electric motor comprising a pair of contacts, means supporting one of said contacts for repeated movement to and from engagement with the other of .said contacts, :means independent of said motor for rapidly moving said one contact with periodic regularity at a speed independent of said motor speed, the last mentioned means includ-ing an impedance, means adapted to connect: sa-id contacts in parallel with said impedance and in. serieswith said motor and a source of electrical power, and means t-o adjust thfe position of the other of 'd contacts relative to said one contact during operation of the controller t0 thereby vary the duration of closing of t-he contacts, whereby the periodic closing of said contacts energizes the motor with pulses of electrical power at vfull line voltage and the speed of the mot-or is determined by the duration of said pulses.

2. A speed controller as defined in claim l and further comprising manually operable switch means in series with said sourcerof electrical power and said contacts, and a single manual-ly operable means cooperating with said other contact land said switchmeansfor sequentially effecting actuation of said. switch means and controlling the posit-ion ofsaid other contact.

3. A speed controller for an electric motor comprising an electromagnet, amovable armature for said electromagnet, an electrical contact mounted for movement with said armature, a second electrical contact adapted to be engaged by said first contact when the latter is moved toone position by energization of said electromagnet, the said `contactsbeing adapted` to be disengaged by move-ment of said armature and firstV contact to a second position when said elcctromagnet is deenergized, means adapted to connect the said electromagnet in series with the motor to be controlled and a source of electrical power, and` means connecting said contacts in parallel with said electromagnet, whereby the said contacts are repeatedly opened and closedwith .each closing of the said contacts short circuiting the said electromagnet so that the. motor is energized by pulses of electrical energy at substantially full line voltage.

4. A speed controller for an electric motor comprising an electromagnet, a movable armature for said electromagnet, an electrical contact mounted for movement with said armature, a second electrical contact adapted to be engaged by said first contact when the latter is moved to one position. by energization of said electromagnet, the said contacts being. adapted to be disengaged by movement of said armature and said rst contact to a second position when said electromagnet is deenergized, means adapted to connect the said electromagnet in series with the motor to be controlled and a source of electrical power, means connecting said contacts in parallel with said electromagnet, andmeans to adjust the position of said second contact relative to said first contact, whereby the said contacts are repeatedly opened and closed with each closingV of thc said contacts short circuiting the said electromagnet4 so that the motor is energized by pulses of electrical energy at substantially full line voltage and the: speedv of the motor is determined by the duration of engagement of the. contacts.

5. A.v speed controller for an electric motor comprising an electromagnet, an armature :for sa-id electromagnet supported for vibratory movement in response to energization. and deenergization of said electromagnet, an electrical. contact mounted for movement with said armature, a second. Contact adapted to be engaged by said rst contact when. the latter is. vibrated, means adapted to connect the saidselectromagnet in series with the motor to. be-controlled and a. source ofv electricalpower, means connecting said.. contacts. in, parallel. with said electromagnet, and means to adjust one of said contacts relative to the other contact to vary the duration of their engagement, whereby the said contacts are repeatedly opened and closed with each closing of the said contacts short circuiting the said electromagnet so that the motor is energized by pulses of electrical energy at substantially full line voltage and the speed of the motor is determined by the duration of engagement of the contacts.

6. A speed controller as defined in claim and further comprising means to dampen the vibration of said armature and thereby control the frequency of the pulses of full line voltage supplied by the controller.

7. A speed controller as defined in claim 5 and in which( the said armature is supported as a cantilever.

8. A speed controller as defined in claim 5 in which the said armature comprises. a plate-like spring having a central opening, and a tongue-like member connected with said armature and projecting into the said opening with the first-mentioned contact mounted on said tonguelike member adjacent the free end thereof.

9. A speed controller for an electric motor comprising an electromagnet, an armature for said electromagnet at least a portion of which is resilient and is so supported that the armature vibrates in response to energization and deenergization of said electromagnet, an electrical contact mounted for movement with said armature, an adjustable contact movable towards and away from said first-mentioned contact and adapted to be engaged by said first contact when the latter is vibrated, the range of adjustability of said adju-Stable contact including a position thereof in which the contacts remain in continuous engagement, means adapted to connect the said electromagnet in series with the motor to be controlled and a source of electrical power, and means connecting said contacts in parallel with said electromagnet, whereby the said contacts are adapted to be repeatedly opened and closed with each closing of the said contacts short-circuiting the said electromagnet so that the motor is energized by pulses of electrical energy at substantially full line voltage and the speed of the motor is determined by the duration of the intervals in which the said contacts remain closed, the motor being continuously energized when the said adjustable contact is positioned to continuously engage said first contact.

10. A speed controller for an electric motor comprising an electromagnet, an armature for said electromagnet supported for vibratory movement in response to energization and deenergization of said electromagnet, an electrical contact mounted for movement with said armature, a second electrical contact adapted to be engaged by said first contact when the latter is vibrated, means adapted to connect the said electromagnet in series with the motor to be controlled and a source of electrical power, means connecting said contacts in parallel with said electromagnet, means to adjust said second contact relative to said first contact and thereby regulate the duration of engagement of said contacts during each vibration of said first contact, the last-mentioned means including a manually movable member and cooperating cam surfaces Ifor transmitting movement of said member to said adjustable contact.

1l. A speed controller as defined in claim 10 and further comprising means normally urging said member to a position in which the said cam surfaces are disengaged, and means electrically connecting said cam surfaces in series with the said electromagnet and motor so that the said cam surfaces constitute a switch which is closed by the initial engagement of the said cam surfaces.

12. A speed controller for an electric motor comprising `a mounting plate, an electromagnet mounted on said plate, an armature for said electromagnet, means connected to lsaid plate and providing a cantilever-type support for `said armature whereby vibratory movement is imparted to said armature and supporting means in response vto energization and ydeenergization of said elec- 10 tromagnet, an electrical contact carried by saidarmature supporting means for vibratory movement therewith, a second electrical contact, electrical conductive means supporting said second contact upon said plate inline with the path of movement of said first contact, a member movably `supported upon said plate and adapted to be moved relative thereto into vengagement with the supporting means for said second contact to move the latter towards said first contact, the portion of said member which engages said contact supporting means being electrically conductive, force exerting means normally urging said movable member out of engagement with said contact supporting means, a first electrical terminal member conductively associated with the conductive portion of said movable member, and a second electrical terminal member connected with said first contact and one lead of said electromagnet, the other lead Iof said electromagnet being connected to the supporting means for said second contact, whereby a motor connected in series with said terminal members and a source of electrical power is energized at full line voltage at any desired speed by movement of said movable member against the action of said force exerting means, the speed of the motor being selected Aby the extent of said movement of the movable member, and the motor 4being deenergized when the movable member is allowed :to return to its initial position under influence of said force exerting means.

13. A speed controller as defined in claim 12. and further comprising a substantially U-shaped magnetically permeable member having one leg connected to said plate and the other leg spaced therefrom, the said electromagnet being supported upon said U-shaped member in a manner such that the said other ieg thereof constitutes one pole piece lfor the electromagnet, the said armature supporting means having one end connected with said one leg of the U-shaped member and extending transversely therefrom so that the said armature has a portion .thereof disposed adjacent the said other leg of the U-shaped member.

14. A speed controller as defined in claim 13 and :Eurther comprising a condenser mounted upon said U-shaped member andY electrically bridged about the said contacts.

15. A speed controller for an electric motor comprising an electromagnet, a movable armature for said electromagnet, an electrical contact mounted for movement with said armature, a second electrical contact adapted to be engaged by said first contact when the latter is moved to one position -by energization of said electromagnet, the said contacts being adapted to 4be disengaged yby movement of said armature `and first contact to a second position when said electromagnet is deenergized, means adapted `to 4connect the said contacts in ser-ies with the motor to be controlled `and a source of electrical power, and means to connect said electromagnet with [a] said source of electrical power so that the electromagnet is repeatedly energized and deenergized by the operation of said contacts and independently of the speed of the motor, whereby the said contacts are repeatedly lopened and closed with each closing of the said contacts supplying a pulse of electrical energy to said motor at substantially full line voltage.

[16. A speed controller as defined in claim l5 and further comprising means to adjust the position of said second contact relative to the first-mentioned contact to thereby vary the duration of closing of the contacts during each engagement thereof and correspondingly vary the speed of the motor] 17.' A speed controller for an electric motor comprising `an electromagnet, a pair of contacts connected in parallel with said electromagnet, means supporting one of said contacts for movement to and from engagement with the other of said contacts with periodic regulation in response to repeated energization and deenergization of said electromagnet, and means adapted to connect said contacts. in series with. said motor .and a sour-ce of velec- `trical power, whereby repeated energization. and deencrgizationof ysaid:` electromagn'et effects periodic closing -of said contacts so that the moto'r is energized: with pulses `ofelectrical powerv at full line voltage and the speed of the motor is determined by `the duration of said pulses.

18. A speed controller for an electric motor comprising anv electrtimagnet, a movable armature for said electrornagnet,- an electricalv contact: mounted for movement with saidy armature, a secondv electrical- Contact adapted to be engaged. by said rst Contact when the latter' is moved tojone vposition byr energzationof said electromagnet, the said contacts being adapted to. be disengaged by movement of said armature and first contact to a secon-dy position when said electromagnet is deenergzea', meansl adapted; t0 connect the saidcontacts in series with the motorta be controlledA andi a source of. electrical power, means to connect said electrornagnetl with said source of electrical power so that the elec-tromagnet is repeatedly energized and deenergized independently of the speed of the motor, whereby the said contacts are 12 repeatedlyl opened'and closed with each closing of the said 'contacts supplying a pulse of electrical energy to said motor at substantially full line voltage, and means to adjust the position of said second contact relative to the first mentioned Contact to thereby vary the duration of closingI of the Contact during each movement thereof and correspondingly vary the speed of the motor.

References Citedin the le of this patent. or the original patent

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