US2512405A - Centrifugal mechanism - Google Patents

Description

J1me 1950 s. o. WlLLlTS ETAL 2,512,405

czmrwam. uncumxsu Filed May 22, 1948 Inventor-s: Glenn D.Wi||ics, Lawrence W.Wightman,

Their AttoPney.

Patented June 20, 1950 CENTRIFUGAL MECHANISM Glenn D. Willits, Leo, and Lawrance w. Wightman, Fort Wayne, Ind., assignors to General Electric Company, a corporation of New York Application May 22, 1948, Serial No. 28,538

Claims.

This invention relates to centrifugal mechanisms and more specifically to such mechanisms of the type used for operating switches adapted to control the circuits of starting windings of dynamoelectric machines.

The utilization of a centrifugal mechanism mounted on the shaft of a dynamoelectric machine to operate a switch for disconnecting the starting windings after the machine has come up to speed is well known in the art. A necessary characteristic of such a mechanism is a snap action so that excess arcing at the switch contacts may be prevented. In order to receive this snap action, these mechanisms have, in the past, been quite complicated in construction and adjustment utilizing a number of intricate component parts.

An object of this invention is to provide an improved centrifugal mechanism for operating a switch.

Another object of this invention is to provide an improved centrifugal mechanism for operating a switch in which the number of movable parts is appreciably reduced.

A further object of this invention is to provide an improved switch operating centrifugal mechanism for use on the end of a rotatable shaft.

Further objects and advantages of this invention will become apparent and the invention will be better understood from the following description referring to the accompanying drawing. The features of novelty which characterize this invention will be pointed out in the claims annexed to and forming a part of this specification.

In accordance with this invention, there is provided a pivot member secured to a rotatable shaft and a hollow cap member positioned on the end of the shaft and. adapted for sliding axial movement thereon. A coil spring is located within the cap member and is interposed between the end of the shaft and the inner surface of the end of the cap member. The cap member, which is provided with a portion adapted to operate the switch, is biased into one switch operating position by the spring at a speed of the shaft below a predetermined speed. A pair of weight members are pivoted on the pivot member and engage the cap member. 'These weight members are adapted for pivotal movement under the action of centrifugal force in response to rotation of the shaft, and move the cap member against the force of the spring into another switch operating position at the predetermined speed of the shaft.

In the drawing, Fig. 1 is a side elevational view, partly in section, of a dynamoelectric machine provided with the improved centrifugal mechanism of this invention, shown in the stand-still position; Fig. 2 is a detailed illustration of the centrifugal mechanism of Fig. 1, shown in the operated position above the critical speed; Fig. 3 is a view in perspective illustrating the assembly of the various components of this improved centrifugal mechanism; and Fig. 4 is an end view illustratin a modification of this invention.

Referring now to Fig. 1, there is shown a single phase induction motor provided with an outer shell member I with a stationary stator member 2 secured therein. A rotor member 3 is mounted on a rotatable shaft 4 which is rotatably supported in a unit bearing (not shown) mounted in the end shield 5. This machine is provided With a single-phase main field exciting winding 6 and a starting field exciting winding 1 arranged in winding slots in the stator in any convenient manner. The running and starting windings 6 and l are adapted to induce electric currents in the cast squirrel cage winding 8 arranged in suitable slots 34' in the rotor member 3.

In a, single phase induction motor havin separate starting and running windings, it is desirable that the starting field exciting winding should be energized during the period when the motor starts from a standstill, or under such operating conditions that the speed of the motor is reduced below a predetermined value. It is, however, also desirable that the starting field exciting winding be deenergized when the speed of the motor exceeds a predetermined value. In order to accomplish this result, there is provided a switch 9 mounted on a switch support l0 formed of insulating material, which is secured to the end shield H in any suitable manner, such as by screws 12. The switch 9 is provided with electrical contacts I 3 and M which are connected to the energizing circuit of the starting field exciting winding 1.

The switch 9 in Fig. 1 is shown with the contacts l3 and I4 closed so that the starting field exciting winding 1 is energized. As the motor comes up to speed, it is necessary to open contacts I; and I 4 and to accomplish this result, the arrangement now to be described is provided. A pivot member I 5, fabricated from relatively thin sheet material, is secured to the rotatable shaft 4, by means of a, hub portion l6 pressed tightly on the shaft, and abuts the end lamination of the rotor member 3. Each end of the pivot member I is bent over into an axis parallel with the shaft 4 to form pivot plates I! and I8. These pivot plates have cutout portions in which the weight members are pivoted, as will be hereinafter described. A hollow cap member I9 formed of insulating material is positioned on the end of the shaft 4 and is provided with a projection which engages openating arm 2| of the switch 9 which carries contact l4. A coil spring member 22 is positioned within the cap member and is interposed between the end 23 of the shaft 4 and the inner surface 24 of the end of the cap member l9. At the standstill condition and at speeds below the predetermined speed at which the starting field exciting winding is to be disconnected, the spring member 22 biases the cap member I9 into the switch operating position shown in Fig. 1 in which the switch operating portion 20 engages the operating arm 2| to close contacts l3 and H. A pair of weight members 25 and 26, fabricated from relatively thin sheet material, are pivoted on the pivot plates I1 and I8. respectively, each of the weight members being provided with two weight portions 21 which in the assembled position are arranged on either side of the shaft 4 between the pivot plates 11. Each of the weight members 25 and 26 is provided with a central pivot portion 28 which mates with the corresponding cutaway portion 29 of the pivot plates I1 and I8 providing a pivotal mounting for the pivot members 25 and 26. Each of the weight members-25 and 26 is further provided with a pair of projections 30 which are also arranged respectively on either side of the shaft 4', the weight members thus having a U-shaped configuration as shown in Figs. 1 and 2. The cap member I9 is provided with two axial slots 3| in its outer surface which define actuating walls 32. The projections 30 of the weight members 25 and 26 are respectively arranged in the axial slots 3| of the weight members is and engage the walls 32.

It can now be readily seen that as the speed of the motor increases, the weight members 25 and 26 under the action of centrifugal force will pivot on the pivot plates I! and I8 and at the desired predetermined speed will have assumed the position shown in Fig. 2. As the weight members 25 and 26 are pivoted, the projections 30 move the cap member [9 axially along the shaft 4 against the force of the spring 22 into the second switch operating position. At this point, since the switch operating arm 2| is formed of resilient material, the contacts I3 and I4 will be open and the starting field exciting winding 1 disconnected from the support. It will be readily apparent that there is here provided a greatly simplified centrifugal mechanism having only five component parts, i. e., the pivot member l5, cap member 19, spring 22, and weight members 25 and 26. This centrifugal mechanism not only permits ease in assembly, but also provides more accurate control since the bias spring 22 is located in the axisof the shaft 4 and is, therefore, not subject to centrifugal forces. Furthermore, this mechanism has an inherent snap action with a minimum number of parts and there is a desirable large differential between the speed at which the mechanism opens the contacts, or cut out speed, and the speed at which the contacts are reclosed, or cut back speed.

In the embodiment shown in Figs. 1-3, the

pivot member I5 is a separate component which pre-formed and pressed on the shaft 4. It may be desirable to form the pivot member I5 from the end lamination of the rotor 3 and this construction is shown in Fig. 4. Here, prior to assembly, the end lamination 33, in addition to receiving the conventional squirrel cage winding slot punches 34, is also punched to provide the pivot plates I1 and I8. These portions are bent over to their proper positions parallel to the axis of the shaft 4 leaving cutout portions 35 in the end lamination 33. The end lamination 33 may be either the regular laminated stock used for the other laminations, or special steel particularly adapted for this purpose. In this modification, the number of component parts is further reduced since the pivot member is formed from the end lamination of the rotor.

While we have illustrated and described a particular embodiment-of this invention, modifications will Occur to those skilled in the art. We desire it to be understood, therefore, that this invention is not to be limited to the particular arrangement disclosed, and we intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

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

1. A centrifugal mechanism for operating a switch and adapted for use on the end of a rotatable shaft, said mechanism comprising a rotatable pivot member formed of relatively thin material having its central portion, secured to said shaft and its ends respectively arranged parallel with and on either side of said shaft to form pivot plates, a hollow cap member positioned on the end of said shaft and adapted for sliding axial movement thereon for operating said switch, said cap member having two axial slots in its outer surface, resilient means in said cap member interposed between the end of said shaft and the inner surface of the end of said cap member for biasing said cap member into one switch operating position at below a predetermined speed of said rotatable shaft, and two U-shaped weight members formed of relatively thin material and having-their central portions pivoted on said pivot plates, each weight member having two weights respectively arranged on either side of said shaft, each of said weight members having two projections respectively engaging said axial slots of said cap member, said weight members being adapted for pivotal movement under the action of centrifugal force for moving said cap member against the force of said resilient means into another switch operating position at said predetermined speed.

2. A centrifugal mechanism for operating a switch and adapted for use on the end of a rotatable shaft, said mechanism comprising a rotatable pivot member formed of relatively thin material with a central hub portion secured to said shaft and end portions respectively arranged parallel with and on either side of said shaft to form pivot plates, said pivot plates having cut out portions formed therein, a hollow cap member positioned on the end of said shaft and adapted for sliding axial movement thereon for operating said switch, said cap member having two axial slots in its outer surface, a coil spring in said cap member interposed between the end of said shaft and the inner surface of the end of said cap member for biasing said cap member into one switch operating position at below a predetermined speed of said rotatable shaft, and

two U-shaped weight members formed of relatively thin material with their central portions arranged to respectively pivotally cooperate with said out out portions of said pivot plates, each of said weight members having two weights respectively arranged on either side of said shaft intermediate said pivot plates having two projections respectively'engaging said axial slots of said cap member, said weight members being adapted for pivotal movement under the action of centrifugal force for moving said cap member against the force of said spring into another switch operating position at said predetermined speed.

3. A centrifugal mechanism for operating a switch and adapted for use on the end of a rotatable shaft, said mechanism comprising a rotatable pivot member fabricated from relatively thin sheet material with a central hub portion secured to said shaft and end portions respec-' tively arranged parallel with and on either side of said shaft to form pivot plates, said pivot plates having cut out portions formed therein, a hollow cap member positioned on the end of said shaft and adapted for sliding axial movement thereon for operating said switch, said cap member having two axial slots in its outer surface, a coil spring in said cap member interposed between the end of said shaft and the inner surface of the end of said cap member for biasing said cap member into one switch operating position at below a predetermined speed of said rotatable shaft, and two substantially. U-shaped weight members fabricated fromrelatively thin material with their central portions respectively pivotally arranged to cooperate with said out outportions of said pivot plates, each of said weight members having two weights on one end thereof arranged respectively on either side of said shaft intermediate said pivot plates and two projections on the other end thereof respectively on either side of said shaft for engaging said axial slots of said cap member, said weight members being adapted for pivotal movement under the action of centrifugal force for moving said cap member against the force of said spring into another switch operating position at said predetermined speed. i

4. In combination with a dynamoelectric machine rotor formed of laminated material and mounted on a rotatable shaft, a centrifugal mechanism for operating a switch, said mechanism comprising a rotatable pivot member formed from the end lamination of said rotor and secured anism for operating a switch,

movement under the action of centrifugal force for moving said cap member against the force of said resilient means into another switch operat ing position at said predetermined speed.

5. In combination with a dynamoelectric machine rotor formed of laminated material and' mounted on a rotatable shaft, a centrifugal mechsaid mechanism comprising a rotatable pivot member formed from the end lamination of said rotor and secured to said shaft, a hollow cap member positioned on the end of said shaft and adapted for sliding axial movement thereon for operating said switch, said cap member having two axial slots in its outer surface, a coil spring in said cap member interposed between the end of said shaft and the inner surface of the end of said cap member for biasing said cap member into one switch operating position at below a predetermined speed of said rotatable shaft, and two weight members pivoted on said pivot member, each of said weight members having two weights respectively on either side of said shaft and two projections respectively on either side of said shaft for engaging said axial slots of said cap member, said weight members being adapted for pivotal movement under the action of centrifugal force for moving said cap member against the force of said spring into another switch operating position at said predetermined speed.

GLENN D. WILLITS. LAWRANCE W. WIGHTMAN.

REFERENCES CITED The following references are of record in th flle of this patent:

UNITED STATES PATENTS

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