US2209241A - Control device - Google Patents

Description

July 23, 1940. TREUBERT 2,209,241

CONTROL DEVICE Filed May 19, 1938 Fig].

M l o /9 A? 2/ Inventor: Ludwig Treuberc, by

Has Attorney,

Patented July 23, 1940 UNITED STATES mean CONTROL ncvron Ludwig T'reubert, Dresden, Germany, assignor to General Electric Company, a corporation of New York Application May 19, 1938, Serial No. 208,943- In Germany June 25, 1937 2 Claims.

This invention relates to control devices, more particularly to step by step control devices such as manually operated starting switches for electric motors, and has as its object simple and reliable means for holding the movable member of the device in any one of several positions and for returning said member to a starting position in the event offailure of voltage.

In one form, the invention consists of a voltage drop release device for step by step switches or the like wherein the switch shaft is provided with an electromagnetically operated brake which normally holds the shaft in a desired position against the tension of a spring. In the event of failure of the voltage supply, the electromagnet of the brake is deenergized and the switch is thrown to an off position by the spring. More over, the holding force of the brake is regulated in dependence upon the position of the switch so that the braking force is just sufficient to overcome the force supplied by the spring. This braking force can be overcome by the operating means for the switch so as to move the switch to a different desired position.

For more complete understanding of the invention, reference should be had to the accompanying drawing, Fig. l of which is an enlarged fragmentary view mostly in section showing an electromagnetic brake applied to a rotary motor starting switch in accordance with this invention, while Fig. 2 is a wiring diagram showing a rotary starting switch having the construction of Fig. 1 connected to control an electric motor.

Referring to the drawing, the invention is shown as applied to a motor starting and speed regulating switch consisting of a control arm I secured to a shaft I I which is rotatably mounted in a bearing provided for it in a supporting plate base 52 preferably made of electrically insulating material. On the base l2 are a plurality of concentric arcuate contacts or arcuate series of contacts consisting of an inner solid ring l3, an outer circular row of spaced contacts I4 terminating in a solid contact I5, a third concentric solid contact I6 and a plurality of contacts I! and a fourth solid contact I8. The switch arm II) is provided with sliding contact members electrically connected to each other and respectively engaging and making electrical contact with the concentric contacts as the switch arm is moved over them.

In the operation of this control switch, the arm I0 is moved during the starting operation in a clockwise direction, its longer end I9 start- (01. zones) ing from the off position indicated by the insulated segments 20. With the connections shown in Fig. 2 in the circuit of an electric motor, the supply switch 2| being closed, the switch arm Iii first completes a circuit for the field winding 22 of the motor through the contact I6 and the switch arm to the inner contact I3, which is connected to one side 2 la of the supply source. Also the circuit for the armature 23 of the motor is established from the contact I3 through the switch arm to some one of the contacts I4 and through starting resistances (not shown) connected across the contacts M through the contact I to the armature of the motor. As the arm is turned farther, the resistance in the armature circuit of the motor is cut out to bring the motor up to speed until the segment I5 is reached. The field circuit of the motor is unchanged until the switch arm ill reaches the contacts I! thereby inserting in the field circuit resistances (not shown) connected across these contacts whereby the field strength and hence speed of the motor are regulated.

Referring to Fig. 1 in accordance with the invention, the lower end of the switch arm shaft I I is provided with a disc 26 which is splined to the shaft I I so as to be movable a short distance axially of the shaft. This disc is provided with a beveled friction brake surface 25 on its upper side which fits in the beveled end of a cylindrical member 26 secured by a screw 21 to the support 52. In order to provide a flux path for the brake magnet coil 28, the cylindrical member 26 and the disc 24 are made of magnet core iron. The coil 28 surrounds the shaft II but is preferably secured to the cylindrical member 26 so as to be stationary. By means of a helical spring 29 surrounding the cylindrical member 26, the shaft II is biased to its off position, movement of the switch arm ll] from the off position winding up the spring 29.

As shown in Fig. 2, the brake coil 28 is preferably energized just before and during the time that the switch arm II is in its regulating position in engagement with some one of the contacts ll. As shown, the coil 28 is connected to the conducting contact I8 and has its other terminal connected directly to the supply conductor 2 to. It is thus arranged so that when the switch it reaches the contact I8, the coil 28 is connected directly across the supply source through the contact arm Ill to the segment I3 and therefore, the brake coil 28 acts as a zero voltage coil.

When the coil 28 is energized, the disc 24 is drawn by the coil to bring its beveled brake surface into engagement with the similar surface on the cylindrical member 26 with sufiicient force to hold the switch arm I against the return force supplied by the spring 29. Thus the switch arm is secured in that position. Also the braking force is not great enough to prevent further movement of the switch arm in either direction as desired, the switch arm being forceably moved against the action of the brake. Preferably the contact segment I8 acts as an electrical resistance to regulate the energization of the coil 28, and thereby the brake force, in proportion to the increase in force applied by the spring 29 as the switch is advanced in such a, manner that the braking force at all times is just sufiicient to hold the switch arm in place against the spring. If desired, the segment i8 may be in the form of a series of contacts corresponding to the contacts I! with resistances connected between them.

In the event of failure of the supply source voltage the coil 28 is deenergized and releases the brake whereupon the spring 29 returns the switch a'rmWllto its starting position. Also the same action obviously takes place in the event that the switch 2! is opened to stop the motor.

What I claim as new and desire to secure by Letters Patent of the United States is:

Amotor starting and speed regulating control device comprising a movably mounted control member, a spring biasing said control member'to a predetermined starting position, electric contact'means in the path of movement of said control member from said starting position to an intermediate position, motor armature starting resistance means connected electrically to said contact means, means on said control member engaging said contact means to cut out said resistance for starting of a motor during movei ent of said control member to said intermedi'ate'position, speed regulating contact means arranged in the path of said control member from said intermediate position to a final position, motor field regulating resistance means connected to said speed regulating contact means, means carried by said control member cooperating with said speed regulating contact means to insert said field regulating resistances in the field circuit of a motor in moving from said intermediate position to said final position and'thereby regulate the speed of the motor, a pair of brake members having engaging frictional surfaces, means securing one of said brake members to said control member, supporting means securing the other of said brake members against movement, a coil arranged when'energized to hold said brake members into engagement with each other, brake resistance contact means in the circuit of said coil arranged in the path of movement of said control member between said intermediate and said final positions, means carried by c said control member cooperating with said brake resistance contact means to close the circuit of said coil when said control member is moved to said intermediate position and thereafter to vary the energization of said coil so as to increase the frictional engagement between said brake members with increase in the force applied to said control member by said spring as said control member is -moved toward said final position and thereby hold said control member in any position on said speed regulating contact means.

2. A motor starting and speed regulating control device comprising a pivotally mounted con- 'trol member, a spring biasing said control member to a predetermined starting position, a series of contacts in the path of movement of said control member from said starting position to an intermediate position, motor armature starting resistances connected electrically between said contacts, means on said control member engaging said contacts to cut out said resistance for starting of a motorduring movement of said control member to said intermediate position, a series of speed regulating contacts arranged in the path of said control member from said intermediate position to a final position, motor field regulating resistances connected between said speed regulating contacts, means carried by said control member cooperating with said speed regulating contacts to insert gradually said field re ulating resistances in 'the'field'circuit of a motor in moving from said intermediate position to said final position and thereby regulate the speed of the motor, a pair of'brake members having annular engaging frictional surfaces in concentric relation with the axis of said control member, means securing one of said brake members to said control member, supporting means securing the other of said brake members against movement, a coil arranged when energized to hold said brake members in engagement with each other, brake regulating resistance means in the circuit of said coil arranged in the path of movement of said control member between said intermediate and said final positions, means carried by said said control member by said spring as said con-,

trol'member is moved toward said final position and thereby hold said control member on any one of said speed regulating contacts.

LUDWIG TREUBERT.

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