US3155796A

US3155796A - Hot wire starting switch for singlephase induction motors

Info

Publication number: US3155796A
Application number: US104655A
Authority: US
Inventors: Ellenberger Jakob
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-04-15
Filing date: 1961-04-21
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03
Also published as: DE1413779A1

Description

NOV. 3, J ENBERGER HOT WIRE STARTING SWITCH FOR SINGLE-PHASE INDUCTION MOTORS Filed April 21, 1961 4 Sheets-Sheet 1 N MOTORS 1964 J. ELLENBERGER HOT WIRE STARTING SWITCH FOR SINGLEPHASE INDUCTIO 4 Sheets-Sheet 2 Filed April 21, 1961 Nov. 3, 1964 J. ELLENBERGER 3,155,796

HOT WIRE STARTING SWITCH FOR SINGLE-PHASE INDUCTION MOTORS Filed April 21, 1961 4 Sheets-Sheet 3 Nov. 3, 1964 J. ELLENBERGER 3, 9

HOT WIRE STARTING SWITCH FOR SINGLE-PHASE INDUCTION MOTORS Filed April 21. 1961 4 Sheets-Sheet 4 United States Patent M 3,155,796 H01 WERE STARTING 5WITH FQR SENGLE- PHASE INDUQTHJN MGTQRS .l'ahob Ellenherger, Ziegelweg 632, Aitdorf, near Nnrnherg, Germany Filed Apr. 21, M61, Ser. No. 1il4,655 Claims priori" application Germany, Apr. 23, 1966, E 19,249; Apr. 15, 1961, E 26,933 3 Qlaims. (Cl. zen-r22 The present invention relates to a starting switch for single-phase induction motors which is provided with a pivotable contact carrier, the contact of which separates from its associated contact when the rated speed of the motor is reached, and with a heating wire lying in the motor circuit, one end of which is secured to a pivotable lever which is acted upon by a spring and is connected to the contact carrier.

A known starting switch of the type has a pivotable lever which is connected not only to the contact carrier of the starting switch, but also to the contact carrier of a motor-protective switch. This known switch therefore constitutes a combination of a starting switch with a motor-proteotive switch. This requires that the heating wire must be of very accurate dimensions so that both switches will be reliably released separately from each other. Furthermore, the contact carrier and the heating \m're of this known starting switch extend at an oblique angle to each other and are offset relative to each other. This arrangement has the disadvantage that the size of the switch will thereby be increased.

It is the object of the present invention to provide a starting switch of the above-mentioned type which may be produced in a very simple manner and may be made small in size. in order to attain this object, the present invention provides that the contact carrier and the heating wire are arranged substantially parallel opposite to each other and that the pivotable lever is made in the form of an angular lever, one arm of which extends vertically to the contact carrier and to the heating wire and the free end of which is connected to the heating wire, while the other arm extends in the direction of the contact carrier and is connected thereto.

The contact carrier, the heating wire, and the angular lever of the switch according to the invention togcther form approximately a rectangle which substantially defines the size of the switch. The switch according to the invention may therefore be made of a very compact size. This is very important in a starting switch since it must be mounted either on the single-phase induction motor or within the housing of this motor.

In order to simplify the production or" the switch, the invention further provides that the contact carrier and the associated arm of the angular lever will be made of one piece. The contact carrier then forms the longer arm of the angular lever, while the shorter arm. forms the connection to the heating wire. The angular lever is pivotably mounted at a point near the point of engagement of the heating wire. Thus, a long lever arm will be formed for the movable contact.

Due to the arrangement of the movable contact on the end of the long arm of the angular lever, a relatively large transmission ratio will be attained between the point of engagement of the heating wire on the short arm of the angular lever and the contact of the angular lever so that a large connecting movement will be attained even though the heating wire expands for only a small distance.

in order to attain a pivoting movement of the angular lever with as little inertia as possible when the heating wire is heated, the longer arm of the angular lever which forms the contact carrier is recessed whereby the cross Patented Nov. 3, 1964 sectional area of this long arm as well as the weight thereof will be reduced.

According to a further feature of the invention, the angular lever may be arranged so that, when the main winding and the heating wire which is connected in series therewith are without current, the contact carrier will be located in the disconnecting position, while when the heating wire is heated by the strong starting current, the contact carrier will be moved to the connecting position. When the heating wire is cold, the contact of the contact carrier therefore does not engage with its associated contact. The heating wire will therefore not be expanded until heated by the high starting current, and it will then be expanded to such an extent that the contacts of the angular lever will engage under the action of a spring after approximately one to two seconds with the associated contact, whereby the starting winding will be supplied with current. The motor can then run up to its rated operating speed. As soon as the motor has reached its rated speed, the starting current will decrease automatically to the strength of the normal operating current which is not suflicient to expand the heating wire to such an extent that the contact of the contact carrier will further remain in engagement with the associated contact. The contact of the contact carrier therefore separates from the associated contact after the motor has started to run and it remains in this position during the entire operaion during which the starting winding is also disconnected. If during the starting any kind of disturbances occur in the starting switch according to the invention which may delay the starting procedure, for example, by an overload, the starting winding will not be disconnected until the starting has been completed since the actuation of the starting switch depends upon the size of the motor current.

For simplifying the manufacture and installation of the starting switch according to the invention, the shorter arm of the an ular lever is pivotably mounted on the edge of a bent portion of a terminal strip which is secured to a supporting plate of insulating material. This results in a simple mounting of the angular lever and also in a saving of material so that the switch according to the invention may be made of a small size. For actuating the angular lever when the heating wire expands, a compression spring is provided which acts upon the shorter arm of the angular lever at the side of its mounting opposite to the heating wire, while the other end of the spring rests on a bent portion of the terminal strip. This construction also assists in making the switch according to the invention of a small size.

According to a further embodiment of the invention, a contact spring which carries the contact which is associated with the contact of the angular lever is arranged parallel to the longer arm of the angular lever in a rectangular configuration. The contact spring may be secured by means of a rivet or a single spot weld to an angular arm of a second terminal strip which is secured to the supporting plate, and it may be secured in its position on this arm at both sides of it place of securement by means of projections which are pressed out of the angular arm.

In order to attain an accurate adjustment of the tension of the heating wire and of the distance between the contact of the angular lever and its associated contact, the invention further provides that the other end of the heating wire is connected with an angular member, one arm of which secures the heating wire and is pivotably mounted at its free end on or adjacent an end of a bent portion of a third terminal strip which is secured to the supporting plate, while the other arm thereof carries a micrometer adjustment screw, the end of which engages upon the bent portion of the third terminal strip. When ml? the adjustment screw is turned in one or the other direction, the tension of the heating wire will be either increased or reduced with respect to the compression spring of the angular lever, and at the same time an accurate adjustment will be made of the distance between the contact of the angular lever and the associated contact on the contact spring.

For reliably preventing the heating wire from being overheated, the invention further provides protective means comprising an additional contact on the side of the associated contact which is mounted on the contact spring, that is, on the side opposite to the contact on the angular lever. If the heating wire is heated considerably and expanded accordingly, the contact on the angular lever presses under the action of the compression spring the associated contact against this further contact, so that the heating wire will thereby be short-circuited and will then be able to cool off. The heating of the heating wire will thus be limited and it will be absolutely prevented from being overheated. According to another feature of the invention, the supporting plate on which all parts of the switch according to the invention are secured is disposed vertically to a base plate and is made integral therewith. According to another feature of the invention, the heating wire is mounted parallel to and in the vicinity of these two plates. Since great tensions may occur in the heating wire, the one-piece construction of the two plates and their angular arrangement to each other insure that these tensions of the heating wire will be safely taken up. In order to increase the stability of this embodiment of the starting switch according to the invention, the rib is molded on the supporting plate parallel to the heating wire and to the base plate. This rib supports the bent portion which serves for mounting the angular lever. For simplifying the production of the switch, the bearings for the angular lever and the angular member are produced by stamping.

According to a further feature of the invention, the contact carrier is made in a manner known as such in the form of a snap element which is provided with a tilt-' ing member which is acted upon by the arm of the angular member which faces toward this member. Such a snap element has the advantage that it permits a delay of the connecting and disconnecting processes, either of which does not occur until the tilting point has beenexceeded.

In starting switches with heating wires which are provided with a control element which is not a snap element, the following disadvantages may occur. If the starting switch is designed so that in the cold state of the heating wire the movable contact is in engagement with the associated contact, it may occur that the heating wire will become heated so quickly that the starting circuit will be switched off before the motor has run up to its normal operating speed. If the switch is designed so that when the heating wire is cold, the movable contact does not engage with the associated stationary contact and only engages therewith when the heating wire is heated, it may occur when the auxiliary phase is disconnected that the discharge current impulse of the starting condenser will heat the very sensitive heating wire and expand the same to such an extent that the contacts will be closed and the starting circuit will again be connected. These disadvantages will be reliably prevented by means of the snap element. The heating wire must expand for a longer period of time before the tilting point of the snap element will be reached. Furthermore, the discharge current impulse of the condenser will then not be sutlicient at the time when the starting circuit is being disconnected to heat and expand the heating wire to such an extent that the contacts will again be closed.

According to another feature of the invention, the tilting member is made in the form of a bent leaf spring and is mounted at one end thereof in a substantially V- shaped recess in the other arm of the angular lever, while the other end of the leaf spring engages upon an dge of an aperture in the contact carrier. When the heating wire is heated, it will expand and thereby release the angular lever so that the latter can turn under spring action about its pivot point, whereby the leaf spring will be moved beyond its tilting point and the contact carrier will thereby he suddenly pivoted to its disconnecting posi tion.

In order to reduce the weight of the contact carrier to a minimum, the aperture therein is enlarged up to a point near the end of the contact carrier facing away from the contact. The rear inner edge of the aperture is then utilized for pivotably mounting the contact carrier. For this purpose, this inner edge engages into a substantially V-shaped recess from the outer side of the arm of the angular lever which extends vertically to the heating wire or to contact carrier, and in the vicinity of the vertex of the angular lever. The contact carrier itself may be made of a leaf spring, although it does not have to exert any spring action since it is merely subjected to tension by the tilting member which is made in the form of a bent leaf spring. Directly underneath the V-shaped recess, the angular lever is mounted in a vertical bent portion of a terminal strip. For this pivotable mounting the angular lever is provided with lateral notches into which the lateral edges of. an aperture in the vertical bent portion of the terminal strip engage. By this construction it is possible to simplify the manufacture as well as the installation of the starting witch according to the invention.

For tightening the heating wire and for actuating the angular lever a compression spring is provided, one end of which engages upon the angular lever underneath the notches, while the other end engages upon a vertical part of the vertical bent portion of the terminal strip. The compression spring is mounted in this manner so as to be well protected.

In order to permit an accurate adjustment of the tilting point of the snap member or of the pivoting distance of the angular lever, an adjustable screw which in the disconnecting position of the contact carrier engages upon a stop is screwed in the vicinity of the tilting member into the arm of the angular lever which faces toward the contact carrier. The tilting point of the snap member or the pivoting distance of the angular lever may also be influenced by a tightening device for the heating wire. This tightening device is provided with a lockable slide member on which one end of the heating wire is secured and which is slidable in the direction of the heating wire. This slide member is guided between vertical bent portions on a second terminal strip. These vertical portions are arranged in a space saving manner between the contact carrier and the heating wire. This arrangement contributes to the desired result that the starting switch according to the invention will be as small as possible. ment of the slide member and thus of the tension of the heating wire, this slide member is provided with a bent portion which extends transverse to the sliding direction and into which a screw is inserted which engages into a recess in the bent portion of the second terminal strip. Since the screw for the adjustment of the slide member engages into a recess .of the bent portion, the advantage is attained that the slide member will be held at the bent portion so that a lateral shifting of the slide member will be reliably prevented. slide member from tilting, one of 'the bent portions of the second terminal strip is provided with an angular portion which surrounds the slide member at its inner end.

This insures a reliable and simple guiding oftheslide member at the bent portions of the second terminal strip. I

One of the bent portions of the second terminal strip is provided with the stop for the screw which is secured According to a further embodiment it in the angular lever. of the invention, this stop may also form a contact.

In order to permit a very accurate adiustin order to prevent the the adjustment screw which is secured in the angular lever engages upon this contact, the heating wire will be short-circuited through the angular lever and the slide member so that the heating wire will thus be prevented from overheating, since after being short-circuited it will cool off.

According to another feature of the invention, the terminal strips form the supports of all parts of the switch mechanism and they are secured to a plate of insulating material which forms a part of the housing. The terminal strips may, for example, be secured to the plate in a simple manner by means of hollow rivets. According to another feature of the invention, the plate is provided within the area of the end of the contact carrier carrying the contact with two vertical projections which are integral therewith and one of which serves as a stop for the contact carrier in its disconnected position.

The various features and advantages of the invention will become further apparent from the following description which is to be read with reference to the accompanying drawings in which- FIGURE 1 shows a side view of a starting switch according to the invention in the opened position;

FIGURE 2 shows a cross section taken along line IIII of FIGURE 1 through the closed switch;

FIGURE 3 shows the same view as FIGURE 1 with the switch element in the connecting position;

FIGURE 4 shows the switch according to FIGURE 1 as seen from above;

FIGURE 5 shows a cross section taken along line VV of FIGURE 1;

FIGURE 6 shows a front View of the closed switch according to FIGURE 1 in its substantially actual size and as seen in perspective;

FIGURE 7 shows a perspective rear view of the switch according to FIGURE 6;

FIGURE 8 shows a circuit diagram of the switch according to FIGURE 1 with the windings of an electric motor;

FIGURE 9 shows a plan view of a modification of the starting switch according to the invention in the connected position and without the housing cap;

FIGURE 10 shows the switch according to FIGURE 9 as seen from the left thereof, in which the housing cap is applied and shown in cross section;

FIGURE 11 shows the same plan view as FIGURE 9 but with the switch in its disconnecting position;

FIGURE 12 shows a cross section taken along line XIIXII of FIGURE '9;

FIGURE 13 shows a cross section taken along line XIII-XIII of FIGURE 9;

FIGURE 14 shows a perspective view of the switch according to FIGURES 9 to 13 without the housing;

FIGURE 15 shows a perspective view of the closed switch according to FIGURES 9 to 13 in its natural size;

FIGURE 16 shows a perspective view of the lower side of the switch according to FIGURE 15;

FIGURE 17 shows a circuit diagram of the switch according to FIGURES 9 to 16 together with the main and auxiliary windings of a single-phase induction motor;

FIGURE 18 shows a circuit diagram similar to that of FIGURE 17, but in which the main winding is connected to a different terminal strip; While FIGURE 19 shows a plan view of a further modification of the starting switch according to the invention in the disconnecting position without the housing cap, and in which the heating wire is shown in the cold position.

The starting'switch as illustrated in FIGURES l to 7 comprises a housing which consists of a supporting plate 1 and a base plate 2 integral therewith and made of an insulating material, for example, molded plastic, and of a cover 3. This cover 3 is secured to supporting plate 1 by means of a screw 4 and a nut 5. By providing the base plate 2 and the supporting. plate I as well as the cover 3 with a groove-shaped recess 5, a dustproof C10- sure of the housing will be attained. For the electric connection of the starting switch, three connecting

terminals

7, 8 and 9 are provided which extend through suitable slots It), 11, and 12 in supporting plate 1 and are provided with bent-over

portions

13, 14, and 15 of a greater width and are secured to the support plate 1 by means of hollow rivets 16. The bent portion 13 has an angular part 17 on the right edge of which an angular lever 13 is pivotably mounted, as shown in FIGURES 1 and 2. For this purpose, the angular lever 1's has two laterally notches 19 into which trunnionlike projections 2t? of the angular part 17 engage. These trunnionlike projections 20 are formed by a cutout into which the angular lever engages at the notches 19.

The longer arm 21 of the angular lever 18 carries a contact 22 which is operatively associated with another contact 24 which is secured to a contact spring 23. The shorter arm of the angular lever 18 carries the right end of a heating wire 26 which is secured thereto by means of a screw 25, as shown in FIGURES 1 and 2. Above the notches 19, the angular lever 18 is provided with a hollow, pressed-out pin 27, and opposite thereto a vertically bent portion 29 on the terminal strip 7 has a similar hollow pin 28. These

hollow pins

27 and 23 support resilient means comprising a compression spring 3t) which acts at one side upon the angular portion 29 and at the other side upon the angular lever 13 and serves for biasing and actuating the latter toward an operating position.

Contact spring 8 has an angular portion 31 on which, as shown in FIGURE 4, contact spring 23 is secured by means of a rivet 32 and locked against rotation by means of a pair of pins or projections 33 which are pressed out of the angular portion 31.

The heating wire conductor 26 is secured by a further screw 25 to an angular member or adjacent lever 34 which is pivotably mounted by means of a slot 35 on the left end 36 of the bent portion 15 of terminal strip 9 which is recessed in accordance with slot 35.

The other arm of the angular member 34 carries a set screw 37 which, as shown in FIGURE 5, engages upon the bent portion 15 of terminal strip 9. This bent portion 15 is bent again at an angle to form a tab 38 with a contact 39 thereon, as shown in FIGURE 5, which is operatively associated with contact For reinforcing the supporting plate 1, the same is provided with a rib 4% which extends parallel to base plate 2 and may be made integral with supporting plate I. Adjacent to a continuous bore 4-1 for receiving the mounting screw rib 40 is provided with a thicker portion 42. Heating wire 25 is provided in the groove which is formed between base plate 2 and rib it). The angular portion I7 on which the anguiar lever 18 is pivotably mounted engages upon the right edge 43 of rib 40 as shown particularly in FIGURE 3.

The operation of the switch as illustrated in the drawings may be best described with reference to FIGURE 8.

Terminal strip 7 of the starting switch is connected to one pole dd of a source of current, terminal strip 8 is connected to the auxiliary phase winding 45 of a singlephase induction motor, and terminal strip 9 is connected to the main winding 46 of this motor. The connecting point 4'7 of the main winding 46 and the auxiliary phase winding 45 is connected to a terminal 4% which may, for example, form the terminal strip or" a motor protective switch.

If the main switch is closed, heating wire 26 together with the main winding td which is connected in series therewith is supplied with the full voltage so that the heating wire will be heated and expanded by the fuli current of the main winding. Spring 3h then pivots the angular lever 18 in a counterclockwise direction as seen in FF- URE 3 and its contact 22 is then brought into engagernent with the associated contact 24 of contact spring 23, as shown in FIGURE 3, the free end of which when in the inoperative position engages upon a projection 1 of supporting plate 1. Consequently, the auxiliary phase or '7 starting winding 45 also receives current so that the motor will start to run. The period required from the moment of switching on the motor to the start of its rotation amounts to approximately one to two seconds. During the following starting procedure, contact 22 remains in engagement with the associated contact 24. As the speed of rotation increases, the current in the main winding 46 decreases. As soon as this current in the main winding 46 has decreased approximately to the strength of the rated current, the heat of heating wire will no longer be sufficient to close the contacts and the auxiliary phase winding 45 will be disconnected and remains disconnected for the entire period of the normal operative condition if during the operation the motor should be overloaded, the auxiliary phase winding will again be connected to the current so that it can operate as a torque support. During the operation of the motor the heating wire will not be further heated so that the return contact will remain constantly open and not cause any disturbances, for example, of radio or television receptions.

If during the starting the heating wire 26 should become heated very strongly and be expanded accordingly, contact 22 on the angular lever 1.8 presses under the action of compression spring 39 the associated contact 24 upon contact 39 against the action of contact spring 23. This results through the angular lever 1.3 and the engaging

contacts

22, 2 and 39 and the angular member 34 in a short-circuiting of heating wire 26 so that the latter can cool, whereby any overheating or" the heating wire will be reliably prevented. independently of this, the pair of

contacts

22 and 24 remains further closed.

The switch according to the modification of the invention as illustrated in FIGURES 9 to 16 comprises a housing which consists of a plate 51 of insulating material and a housing cap 52 likewise of insulating material. Both

housing parts

51 and 52 may be connected to each other by any suitable means. Housing plate 51 carries terminal strips 53, 54-, and 55 which are secured thereto by means of hollow rivets 56. Within the area of rivets 56, housing plate 51 has on its outside a reinforcing rib 51' integral therewith which provides the housin plate 51 with a considerable bending strength to resist the stresses which are caused by the heating wire. Terminal strip 53 has a vertically bent portion 57 on which a contact 5% is secured. This contact 53 is operatively associated with a contact 59 which is rigidly secured to a contact-carrier Contact carrier 66 consists of flat material and is provided with an aperture 61 in order to reduce its weight. The edge 62 of aperture 61 serves as a support of an arcuate leaf spring 63 which engages thereon under tension with one end which for this purpose is provided with a tongue 64 which is pressed out of leaf spring 63 and bent in the direction toward the contact carrier 6%. The opposite end of the arcuate leaf spring 63 is pivotably mounted in a substantially V-shaped aperture 65 in an angular lever 66. In order to prevent leaf spring 63 from sliding oii laterally within the V-shaped aperture 65, leaf spring 63 is provided on its right end with projections 67, as shown in FIGURES 9, 11, and 12. By means of the inner edge 68 of aperture 61 contact carrier 66 engages into a V-shaped aperture 69 in the angular lever 66. Contact carrier 66 is thus pivotably mounted in this V-shaped aperture 69 of the angular lever 66. V

Underneath the V-shaped aperture 69, the angular lever 66 is provided with lateral recesses '76 into which the edges 71 of an aperture 72 of a vertically bent portion 73 of terminal strip 55 engage, as shown in FIGURE 13'. e

The angular lever 66 is thus pivotably mounted in the bent portion 75 of the terminal strip 55. The bent portion 73 is bent at an angle 74 on which resilient means comprising a compression spring 75, engages, the other end of which abuts against the angular lever 66 and biases it toward an operating position thereof. By means of a mounting screw 76 which is screwed into the angular lever 66 and a projection 76 of which serves at the same time as a guide 8 for the compression spring 75, a heating wire 77 is secured to the angular lever 66. The other end of the heating wire 77 is secured to a slide member or adjust lever 79 by means of a rivet 7 8.

The middle terminal strip 54- is provided with two vertical bent portions 8% and 81 which, as shown particularly in FIGURES 9 and 11, serve for guiding the slide member 79 Slide member 79 is provided with a bent portion 32 which extends transverse to the direction of the heating wire 77. A setscrew 83 is screwed into this cut portion 82 and engages into a recess 84 of the vertically bent portion of terminal strip 54-. If set screw 33 is actuated, slide member 79 will be shifted in the direction of heating wire 77, whereby the heating wire will be either tightened or released. Setscrew 33 also prevents slide member 79 from sliding laterally in a direction vertical t0 the plane of FIGURE 9. In order to prevent slide member '79 also from tilting in the same direction, the vertically bent portion 81 of terminal strip 54 is further provided with a vertically bent portion S5 which engages over the inner end of slide member 79. The vertically bent portion 81 is further provided with a contact 36 upon which a screw 87 engages when the contact carrier 66 is in the disconnected position, and which is screwed into the angular lever 66.

The diagram according to FIGURE 17 shows that the auxiliary phase 45 of an electric motor is connected to the terminal strip 53, while one end of the main winding 46 is connected to the terminal strip 54. Both windings t5 and 46 are connected at 47 to a conductor 91 which may be connected, for example, to a motorprotective switch. Terminal strip 55 may be connected by a conductor 92 to the main current supply or to a main switch. According to the diagram as shown in FIGURE 18, the auxiliary phase 45 is likewise connected to the terminal strip 53. The connections for the conductor 52 and the main winding 4-6 are, however, reversed as compared with the diagram according to FIG URES 17.

While in the diagram according to FIGURE 17 only the current of the main winding 46 fiows through the heating wire 77, in the diagram according to FIGURE 18 the heating wire 77 must take up not only the current 01 the main winding 46, but also the current of the starting winding 45. The circuit according to FIGURE 17 is generally applied to motors with high starting currents which are higher than three times the rated current while the circuit according to FIGURE 18 is applied to motors with small starting currents which are smaller than three times the rated current.

The operation of the starting switch as illustrated in FIGURES 9 to 18 is as follows:

When the main switch is closed, the current flows through the main winding 46 as well as through the auxiliary winding 45', that is, as shown in FIGURE 17, through the contacts '53 and 59, the contact carrier 66, the angular lever 66, the terminal strip 55, and, on the one hand, through the conductor 92, and on the other hand, through the terminal strip 54, the slide member 79, the heating wire 77, the angular lever 66, the terminal strip 55, and, the conductor 92. As soon as the motor has reached its normal operative speed and heating wire 77 has been heated and expanded sufiiciently, the angular lever 66 is pivoted counterclockwise under the action of the compression spring '75 as shown in FIGURES 9, 11 and 17. As soon as leaf spring 63 exceeds its tilting point it presses the contact carrier 6% upwardly as seen in the mentioned drawings, and pivots the contact carrier suddenly into the disengaging position as illustrated in FIGURE 11. The auxiliary winding 45 is thus switched off. After this starts, the operating current decreases to its normal strength which is sufficient to maintain the heating wire' 77 V in the position as illustrated in FIGURE 11, in which the contact carrier 66 engages on a projection 93 which is integral with plate 51. If the main switch is opened,

the entire motor circuit will be interrupted. The main winding 46 as well as the heating wire 77 will be without current so that heating wire 77 can contract and thereby return the angular lever 66 against the action of compression spring 75 to the position as indicated in FIGURES 9 and 17. When leaf spring 63 exceeds its tilting point, contact 59 on contact carrier 60 engages with the stationary contact 58. The starting switch is then ready for a new starting operation.

If the heating wire 77 becomes strongly heated, setscrew 87 will engage with contact 86 and thereby shortcircuit the heating wire 77 so that the latter can cool off. This prevents the heating wire 77 from being overheated.

The operation of the starting switch illustrated in FIGURE 18 in connection with the windings of an electric motor is the same as that of the switch according to FIGURE 17. As illustrated in FIGURE 19, it is, however, also possible to design the switch in such a manner that prior to the starting operation the contact carrier 60 will be in its disconnected position in which it engages upon a vertical projection 94 which is integral with plate 51. Contact 59 and the associated contact 58 are then, however, located on the opposite side of contact carrier 60. If in this case the main switch is closed, a current fiows at first only through the main winding 46 and the heating wire 77 which is heated by this current and will thus expand. Due to this expansion, the angular lever 66 will be able to pivot in a counterclockwise direction, whereby due to leaf spring 63, the switch and thus also the auxiliary winding 45 will be connected. The current then flows also through the auxiliary winding 45 so that the motor will start. As soon as the motor has reached its rated speed, the current flowing through the main winding 46 will be reduced to a fraction of the starting current. This reduced current will not be sufiicient to maintain the heating wire 77 in its expanded position. The heating wire will thus contract and thereby pivot the angular lever 66 to its basic position, whereby due to leaf spring 63 the contact carrier 60 will be moved to its disconnected position as shown in FIGURE 19, in which the

contacts

58 and 59 are separated and the auxiliary winding 45 is switched ofi. If in this event the motor might be overloaded during its operation, the auxiliary winding 45 will again be switched on and will thus serve as a torque support.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. A starting switch for a single-phase inducation motor having a main winding and a starting winding comprising, connect and disconnect means for connecting said starting winding in circuit with a source of power for energizing the starting winding to start the motor and for taking said starting winding out of circuit with said power source when said motor is operating substantially at rated speed corresponding to a given load current in said main winding, said connect and disconnect means comprising a pivotally mounted lever having a long lever arm and a short lever arm, a wire conductor connected in operation in series with said main winding and expandable longitudinally by current energizing said main winding, means connecting one end of said wire conductor to said short lever arm physically adjacent to a free end of said short lever arm for actuating said lever between two operating positions for respectively connecting and disconnecting said starting winding, said long and short lever arms and said wire conductor being disposed defining three sides of a rectangular configuration, said long lever arm and said wire conductor being disposed substantially parallel, means comprising resilient means constantly applying a biasing force on said lever for biasing said lever toward one of said two operating positions, adjust means disposed within said rectangular configuration for variably adjusting tension on said wire conductor in opposition to said biasing force to variably adjust said biasing force thereby to vary the value of the biasing force necessary for said resilient means to apply to said lever to actuate said lever to said one operating position as said wire conductor expands and contracts in dependence upon the value of load current in said main winding and passing through said wire conductor, said adjust means comprising a displaceable, adjust lever disposed interiorly of said rectangular configuration and connected to an end of said Wire conductor opposite to an end connected to said short lever arm, means comprising a set screw interiorly of said rectangular configuration for adjus-tably displacing said adjust lever to variably adjust said tension applied to said wire conductor to variably set said biasing force on said resilient means, means interiorly of said rectangular configuration displaceably mounting said adjust lever, a plurality of contacts disposed interiorly of said rectangular configuration efifectively actuated to a closed condition and an open condition by said lever arm when actuated to said two operating positions respectively for connecting and disconnecting said starting winding, one of said contacts being disposed adjacent a free end of said long lever arm facing interiorly of said rectangular configuration, connections interiorly of said rectangular configuration and extending outwardly therefrom for connecting said contacts to said main and starting windings of said motor and including connections for connecting said wire conductor in series with said main winding, whereby said rectangular configuration substantially defines the dimensions of said switch and the values of said rated speed are accurately adjustable.

2. A starting switch according to claim 1, including protective means rendered effective by said wire conductor and said lever for protecting said wire conductor and disposed interiorly of said rectangular configuration and including means comprising said contacts and said adjust lever for by-passing said wire conductor electrically if the load current in said main current exceeds a given value and including means comprising said connections to maintain said switch in series circuit with said main Winding.

3. A starting switch according to claim 2, in which said protective means comprises means comprising other contacts and said adjust lever rendered effective by said lever and said wire conductor upon expansion thereof when said given value of load current is exceeded to continue said starting winding in circuit with said source of power to assist said main winding in torquing said motor.

References Cited in the file of this patent UNITED STATES PATENTS 1,531,722 Adams Mar. 31, 1925 2,388,033 Berninger Oct. 30, 1945 2,418,235 Menzies Apr. 1, 1947 2,689,289 Bell Sept. 14, 1954 2,699,161 Pees Jan. 11, 1955 2,839,634 Clark June 17, 1958 2,896,051 Taylor July 21, 1959 FOREIGN PATENTS 505,726 France Oct. 5, 1920

Claims

1. A STARTING SWITCH FOR A SINGLE-PHASE INDUCATION MOTOR HAVING A MAIN WINDING AND A STARTING WINDING COMPRISING, CONNECT AND DISCONNECT MEANS FOR CONNECTING SAID STARTING WINDING IN CIRCUIT WITH A SOURCE OF POWER FOR ENERGIZING THE STARTING WINDING TO START THE MOTOR AND FOR TAKING SAID STARTING WINDING OUT OF CIRCUIT WITH SAID POWER SOURCE WHEN SAID MOTOR IS OPERATING SUBSTANTIALLY AT RATED SPEED CORRESPONDING TO A GIVEN LOAD CURRENT IN SAID MAIN WINDING, SAID CONNECT AND DISCONNECT MEANS COMPRISING A PIVOTALLY MOUNTED LEVER HAVING A LONG LEVER ARM AND A SHORT LEVER ARM, A WIRE CONDUCTOR CONNECTED IN OPERATION IN SERIES WITH SAID MAIN WINDING AND EXPANDABLE LONGITUDINALLY BY CURRENT ENERGIZING SAID MAIN WINDING, MEANS CONNECTING ONE END OF SAID WIRE CONDUCTOR TO SAID SHORT LEVER ARM PHYSICALLY ADJACENT TO A FREE END OF SAID SHORT LEVER ARM FOR ACTUATING SAID LEVER BETWEEN TWO OPERATING POSITIONS FOR RESPECTIVELY CONNECTING AND DISCONNECTING SAID STARTING WINDING, SAID LONG AND SHORT LEVER ARMS AND SAID WIRE CONDUCTOR BEING DISPOSED DEFINING THREE SIDES OF A RECTANGULAR CONFIGURATION, SAID LONG LEVER ARM AND SAID WIRE CONDUCTOR BEING DISPOSED SUBSTANTIALLY PARALLEL, MEANS COMPRISING RESILIENT MEANS CONSTANTLY APPLYING A BIASING FORCE ON SAID LEVER FOR BIASING SAID LEVER TOWARD ONE OF SAID TWO OPERATING POSITIONS, ADJUST MEANS DISPOSED WITHIN SAID RECTANGULAR CONFIGURATION FOR VARIABLY ADJUSTING TENSION ON SAID WIRE CONDUCTOR IN OPPOSITION TO SAID BIASING FORCE TO VARIABLY ADJUST SAID BIASING FORCE THEREBY TO VARY THE VALUE OF THE BIASING FORCE NECESSARY FOR SAID RESILIENT MEANS TO APPLY TO SAID LEVER TO ACTUATE SAID LEVER TO SAID ONE OPERATING POSITION AS SAID WIRE CONDUCTOR EXPANDS AND CONTRACTS IN DEPENDENCE UPON THE VALUE OF LOAD CURRENT IN SAID MAIN WINDING AND PASSING THROUGH SAID WIRE CONDUCTOR, SAID ADJUST MEANS COMPRISING A DISPLACEABLE, ADJUST LEVER DISPOSED INTERIORLY OF SAID RECTANGULAR CONFIGURATION AND CONNECTED TO AN END OF SAID WIRE CONDUCTOR OPPOSITE TO AN END CONNECTED TO SAID SHORT LEVER ARM, MEANS COMPRISING A SET SCREW INTERIORLY OF SAID RECTANGULAR CONFIGURATION FOR ADJUSTABLY DISPLACING SAID ADJUST LEVER TO VARIABLY ADJUST SAID TENSION APPLIED TO SAID WIRE CONDUCTOR TO VARIABLY SET SAID BIASING FORCE ON SAID RESILIENT MEANS, MEANS INTERIORLY OF SAID RECTANGULAR CONFIGURATION DISPLACEABLY MOUNTING SAID ADJUST LEVER, A PLURALITY OF CONTACTS DISPOSED INTERIORLY OF SAID RECTANGULAR CONFIGURATION EFFECTIVELY ACTUATED TO A CLOSED CONDITION AND AN OPEN CONDITION BY SAID LEVER ARM WHEN ACTUATED TO SAID TWO OPERATING POSITIONS RESPECTIVELY FOR CONNECTING AND DISCONNECTING SAID STARTING WINDING, ONE OF SAID CONTACTS BEING DISPOSED ADJACENT A FREE END OF SAID LONG LEVER ARM FACING INTERIORLY OF SAID RECTANGULAR CONFIGURATION, CONNECTIONS INTERIORLY OF SAID RECTANGULAR CONFIGURATION AND EXTENDING OUTWARDLY THEREFROM FOR CONNECTING SAID CONTACTS TO SAID MAIN AND STARTING WINDINGS OF SAID MOTOR AND INCLUDING CONNECTIONS FOR CONNECTING SAID WIRE CONDUCTOR IN SERIES WITH SAID MAIN WINDING, WHEREBY SAID RECTANGULAR CONFIGURATION SUBSTANTIALLY DEFINES THE DIMENSIONS OF SAID SWITCH AND THE VALUES OF SAID RATED SPEED ARE ACCURATELY ADJUSTABLE.