US2330344A - Starting device for electric motors - Google Patents

Description

Sept. 28, 1943. .J. L. FREEBERG STARTING DEVICE FOR ELECTRIC MOTORS Filed Jan. 15, 1941 mi im W W;

Patented Sept. 28, 1943 UNITED STATES PATENT OFFICE STARTING DEVICE FOR ELECTRIC MOTORS John L. Freiber Cincinnati, Ohio Application January 13, 1941, Serial No. 374,223

8 Claims.

This invention relates to starting devices or starting rheostats for electric motors.

Where motors are operated on circuits of constant potential, as is nearly always the case, by reason of the low armature resistance in all except very small motors, it is necessary to limit the flow of current through the armature until the motor generates a sufficient counterE. M. F. to regulate the current automatically. This limitation of the current during starting is effected by rheostats which consist of resistances capable of carrying the starting current for the limited period required by the motor to come up to speed. The resistance is arranged in steps so that it can be cut out of the armature circuit step by step as the counter E. M. F. increases with the speed.

The principal object of the present invention is to provide a new and improved starting box or rheostat for the purpose mentioned, in which simplicity of construction, consistency of operation and economy in manufacture as compared with starting boxes presently in use, are emphasized.

A further object of the invention is to provide a starting device of the character mentioned, in which adjustments in order to obtain consistency in operation, may, as compared with presently used boxes, be more easily and simply made and maintained.

Another object of the invention is to provide a. starting box which lends itself to compactness of construction, thus adapting it for use under conditions where space is necessarily limited, as for instance in submarine vessels.

With the foregoing and other objects in view, I

Figure 1 is a sectional view of a starting box constructed in accordance with this invention, parts of the interior mechanism however being shown in elevation.

Figure 2 is a plan view of the series of contacts with portions of the circuit completing mechanism.

Figure 3 is a section on line 33 of Figure 2.

Figure 4 is a. section on line 4-4 of Figure 1 on a reduced scale.

Figure 5 is a diagrammatic view of the electrical connections.

The numeral l indicates the casing of my new starting device,.said casing being provided with atop 2 having aflongitudinal slot 3 for the purpose hereinafter mentioned. Mounted on brackets 4 and 5 in the asing l is an inclined bar 6 which is constructed of any. suitable rigid insulating material. Mounted on the bar 6, and insue lated thereby from each other, is a series of con- !tact terminals 1 which are connected at suitable intervals to the resistancefl by means of leads 8. One end of the resistance 8, that is the end con,- nected with the topmost contact I, is conne ted by means of a lead 1 ll with the armature of motor II. The coil (2 of arelease magnet I3 is in a shunt circuit with the line and motor field in accordance with the, practicein various types of starting boxes presently in Mounted so as to extend through the slot 3 of the top 2, is a hollow shaft or sleeve l4 which is adapted to slide in said slot, The shaft, 14 is provided with an operating handle l5 on its upper end, and rollers l6 and ll span the slot 3 and ride on respectively the upper and lower surfaces of the top 2 so as to maintain the shaft l4 in vertical relation above theseries of contacts I of the bar 6. Mounted in the lower end of the hollow shaft I4 is a hollow plunger l8, which telescopically slides freely in the bore of the shaft. A compression spring I9 is mounted in the shaft I4 and p n 8 so that he upp r e d 0i s id spring abuts the lower end of an adjusting screw 20 in e ope a n han le an h lo r nd a s h l r e d of lu ger. th s o eini t e t ct m mber 2 ca ried by he o r .fsce o e pl n er i oc n act with h e s an e o t c 1-. The sp 9 s of s h nsile st n th ha it expansi e e i i ncc orces el minal 2| positively in contact with either of the resistance buttons 1, and this force is of course increased as the buttons successively are placed at higher elevations, thus increasing the co pression. The expansive energy of the spring is such, coupled with the inclination of the con-. tacts, as to move'the plunger downwardly along the contacts whenever the shaft I4 is relieved of a force, either manual ormagnetic', tending to push or hold it at a point of elevation above the lowest or rest button 22 which is not in the circuit. The desired tension is regulated initially and may from tune to time be read usteq by means or'tne adjustment screw 20. T e shaft l4 may be brought into the 11118 circuit by means of a flexible lead 11 desired, however, I prefer to use a bus bar 24 w th which the smart, I4 makes contact by means or a spring conductor 25,. An armature as is mounted on the shaft l4 in such position as to complete the magnetic ci cuit. of release magnet l3 when the shaft is in. its ex treme right position with the contact 2i in circuit with the uppermost or full speed contact 7.

The operation of my new starting device will be apparent from the foregoing description to those skilled in the art to which the same apperable the motor to attain speed in accordance with the usual custom. When the plunger and contact 2i reach the uppermost contact 7, all of the resistance is cut out and the motor is running" under the full potential. In this position the shaft 54 and with it, of course, the plunger and contact 2! are held by the contact of the armature 25 with the release magnet it. When for any reason, as for instance the failure of the line current, the circuit through coil 32 is discontinued, the magnet l3 releases the armature 25, and the'compression of spring it causes the plunger to be forced downwardly carrying the shaft with connectedmechanism to the left end (as viewed in Figure l) of the slot 3 where the contact 2! rests on the open circuit button 22.

From the foregoing descriptionit will be observed that the' operation of my new starting rheostat depends on but one possible variable, that is the compression of spring E9. The angle of the bar 6 and its contacts I and the compressive energy of the spring having been predetermined in their interrelation, and such angle being at all times definitely maintained by the mounting of said bar on rigid brackets 4 and 5 in the casing, the compressiveenergy of spring l9 should for indefinite periods require no alterzontal vertical direction and passing centrally through said support and with the contacting surfaces of said terminals in a plane parallel with the support, a contact member, means for mounting said contact member for movement in a linear direction in one of said horizontal or vertical planes in the direction of ascent of said contact support over said contact members while making sliding contact therewith, compressible means for yieldingly holding said contact memberv against said contact terminals during the movement of the contact member, said angle of inclination of contact terminals with respect to the plane of movement of the contact plunger and the force of the spring means on the contact planebeing such as to cause the contact plunger to automatically descend to the lowermost conation. However, I prefer to provide adjustability for such compressive energy by means of the adjusting screw 29, so that the device may be readily adapted to individual or local conditions and variations easily compensated.

It will be further observed that the mounting of-the series of resistance buttons in alignment upon an inclined non-conductive bar facilitates great compactness of over-allconstruction, as well as economy of dielectric material as compared with the-usual arcuate series of contacts arranged about the center of a rotating shaft. This construction further contributes toeconomy and durability and consistency of operation in the use of a single spring as against the'two or more springs usually employed in starting boxes of current type. 7

While I have described a preferred. application of the principle of my invention, I do not of course desire to be limited to the specific details shown and described but consider as of my inventio-n all such equivalents and similar constructicns as come within the preview of the appended claims. It should also be understood that the present invention is intended for other types of switches, as for instance in lighting switches for theatres, etc. I v a Having thus fully described my invention, what I claim as new and desire to secure by Letter's Patent'i's't' liIn adevice' of the character specified, in combinationwith a resistance, a seriesof contact terminals electrically connected at intervais with said resistance, a'support for said terminals arranged in an inclined position with respect planes at right angles to one'another in an horitact terminal, and means for holding the contact member in position for maintaining contact with the uppermost contact terminal.

2. In a device ofthe character specified, in combination with a resistance, a series-ofcontact terminals electrically connected at intervals with said resistance, a support for said terminals arranged inan inclined position with respect to planes at right angles to one another in an horizontal andvertical direction and passing centrally through said support, and with the contacting surfaces of said terminalsin a plane parallel with the support, a contact member, means for mounting said contact member for movement in a lineardirection in one of said horizontal or vertical planes in the direction of ascent of said contact support over said contact members while making slidingcontact therewith, compressible means for yieldlngly holding said contact member against said contact terminals during the move ment of the contact member, said angle of inclination of contact terminals with respect to the plane of movement of thecontact plunger and the force of the spring means on the contact plane being suchas to cause the contact plunger to automatically descend to the lowermost contact terminal means for adjusting the compression force of compressible means, and means for holding the contact member in position for maintaining contact with the uppermost contact terminal.

3. A starting device for electric motors comprising in combination a casing, a resistance, an insulating support within said casing and mounted at an angle of inclination to a horizontal plane through said casing, a series of contact terminals in alignment on said support insulated thereby from one another with their contact surfaces in a plane parallel with the support, a manually actuable contact plunger mounted in said casing so as to move in the horizontal plane through the casing over said terminals, spring means for yieldingly compressing said contact plunger against said Contact terminals'so as to make electrical contact therebetweenduring the movement of said contact plunger, said angle of inclination of the contact term nal with respect to the plane of movement of the contact plunger and the force bf the spring means on the contact plunger being such as to cause the contact.

plunger'to automatically descend to the lowermost contact terminal, and means for holding the contact. plunger in position for making contact with the uppermost contact'terminal.

4. A starting device for electric'hiotors comprising in combination a casing, a resistance, an insulating support within said casing and mounted at anangle of inclination to a horizon tal plane through said casing, a series of contact terminals in alignment on said support insulated thereby from one another with their contact surfaces in a plane parallel with the support, a manually actuable contact plunger mounted in said casing so as to move in the horizontal plane through the casing over said terminals, spring means for yieldingly compressing said contact plunger against said contact terminals so as to make electrical contact therebetween during the movement of said contact plunger, means for adjusting the compression of said spring means, said angle of inclination of the contact terminal with respect to the plane of movement of the contact plunger and the force of the spring means on the contact plunger being such as to cause the contact plunger to automatically descend to the lowermost contact terminal, and means for holding the contact plunger in position for making contact with the uppermost contact terminal.

5. A starting device for electric motors comprising in combination a casing, a resistance, an insulating support within said casing and mounted at an angle of inclination to a horizontal plane through said casing, a series of contact terminals in alignment on said support insulated thereby from one another with their contact surfaces in a plane parallel with the support, a manually actuable contact plunger mounted in said casing so as to move in the horizontal plane through the casing over said terminals, spring means for yieldingly compressing said contact plunger against said contact terminals so as to make electrical contact therebetween during the movement of said contact plunger, said angle of inclination of the contact terminals contacting surfaces with respect to the plane of movement of the contact plunger and the force of the spring means on the contact plunger being such as to cause the contact plunger to automatically de scend to the lowermost contact terminal, and an electro-magnet for holding said contact plunger in position for making contact with the uppermost contact terminal.

6. A starting device for electric motors comprising in combination a casing, a resistance, an insulating support within said casing and mounted at an angle of inclination to a horizontal plane through said casing, a series of contact terminals in alignment on said support insulated thereby from one another with their contact surfaces in a plane parallel with the support, a manually actuable contact plunger mounted in said casing so as to move in the horizontal plane through the casing over said terminals, spring means for yieldingly compressing said contact plunger against said contact terminals so as to make electrical contact therebetween during the movement of said contact plunger, said angle of inclination of the contact terminal with respect to the plane of movement of the contact plunger and the force of the spring means on the contact plunger being such as to cause the contact plunger to automatically descend to the lowermost contact terminal, and means for holding the contact plunger in position for making contact with the uppermost contact terminal, a bu bar mounted in said casing, and a contact carried by the contact plunger to make slidable contact with said bus bar simultaneously with the contact of plunger with the terminal contacts.

7. A starting device for electric motors comprising in combination a resistance, a casing, a cover on said casing, said cover being provided with an elongated aperture, an insulating support mounted in said casing at an angle of inclination in relation to the cover, a series of contact terminals mounted in alignment on said support insulated thereby from one another with their contacting surfaces in a plane parallel with said support and electrically connected at intervals with said resistance, said terminals being in alignment with and under said aperture, a hollow shaft extending through the cover aperture, means for mounting said shaft in the aperture for movement in the direction of its major axis, a contact plunger telescopically within said shaft and having its lower end arranged to make sliding engagement with said contact terminals contacting surfaces, a compression spring in said hollow shaft adapted to force the contact plunger against said contact terminals during the movement of the hollow shaft, said angle of inclination of the contact terminals contacting surfaces and the force of the compression spring on the contact plunger being such as to cause the contact plunger to automatically descend to the lowermost contact terminal and means for holding said plunger in position for making contact with the uppermost terminal contact.

8. A starting device for electric motors comprising in combination a resistance, a casing, a cover on said casing, said cover being provided with an elongated aperture, an insulating support mounted in said casing at an angle of inclination in relation to the cover, a series of contact terminals mounted in alignment on said support insulated thereby from one another with their contacting surfaces in a plane parallel with said support and electrically connected at intervals with said resistance, said terminals being in alignment with and under said aperture, a hollow shaft extending through the cover aperture, means for mounting said shaft in the aperture for movement in the direction of its major axis, a contact plunger telescopically within said shaft and having its lower end arranged to make sliding engagement with said contact terminals contacting surfaces, a compression spring in said hollow shaft adapted to force the contact plunger against said contact terminals during the movement of the hollow shaft, said angle of inclination of the contact terminals contacting surfaces and the force of the compression spring on the contact plunger being such as to cause the contact plunger to automatically descend to the lowermost contact terminal, and an electromagnet for holding said plunger in position for making contact with the uppermost terminal contact.

JOHN L. FREIBERG.

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