US1935303A - Centrifugal switch - Google Patents

Description

V. WEBER Nov. l4, 1933.

CENTRIFUGAL SWIT/CH Nov. 14, 1933. V. WEBER 1,935,303

CENTRIFUGAL SWITCH Filed May 31, 1932 2 Sheets-Sheet 2 Patented Nov. 14, 1933 UNITED T FiGE This invention relates to improvements in centrifugal switches; and consists in the novel construction hereinafter disclosed.

An object of the invention is to provide a switch 5 of the class indicated which is simple in construction and which may be assembled with a reasonable range of tolerance in the relative position of the parts withoutimpairing successful operation of the device; which will provide for an eiTicient starting contact and will hold the contact during the acceleration of the motor; which will break rapidly at critical speed and within a minimum speed differential; which includes interlocking parts to hold the switch positively in predetermined contact positions; and which will operate with a minimum degree of friction and thus he durable in use.

Additional objects of the invention will appear from the following detail description thereof, taken in connection with the accompanying drawings, in which v Fig. l is a longitudinal section illustrating the position of the parts in contact positien.

Fig. 2 is a view of the same parts illustrating the switch in reverse position. i

Fig. 3 is a cross-section on the line 3-3 of Fig.1.

Fig. 4 is a cross-section on the line r- 4: of Fig. l. Fig. 5 is a cross-section on the line -5 of Fig. 2

Fig. 6 is a detail view of certain of the switch elements approaching contact position.

Fig. l is a view of the same parts moving from contact position.

In the embodiment of the invention illustrated in the drawings, the switch is shown as associated with parts of a motor which include an armature 1 operating in a field structure 2. An armature i shaft 3 extends axially through the armature and projects at one end through a cover plate 4. A sleeve 5 positioned adjacent to the face of the armature is slidably mounted on the armature shaft. The sleeve 5 has a flange 6 formed integral with the outer end thereof. An expansion spring 7 is positioned intermediate the inner face of the flange 6 and the face of the armature. The tendency of the spring '7 is to move the sleeve 5 outwardly from the armature face. A support comprising a plate 8 and side members 9 ateach end thereof is attached to the face of the armature. The members 9 are in the form of a bifurcated plate and pins 10 are supported between said members at each side thereof. Centrifugal weight members are pivoted on said pins ill on opposite sides of the axis of the armature shaft. The weight members include arms ii and arms 12. Between the arms 11 of each of the weight members is a pin 13, which pins traverse the flange 3 at opposite sides of the axis h armature shaft and seat, respectively, in slots i l formed in opposite f ees of the flange 6. e arms 12 which extent i .5 ii are integrally connected with a plate to which the weight blocks 1? are attached. 'i n the armature is at rest, the arms 12 lie p"' with the armature shaft and in the inw justment. In this position the sleeve 5 is outermost adjustment.

When the -armature is revolved, the weights move the arms 12 outwardly, rocking the weight levers to the position shown in Fig. 2. This movement of the weight levers tends to move the sleeve toward the face of the armature against the tendency of the spring 7.. A

sleeve constitutes an actuator for the sw tch said actuator being controlled by the centri force of the weight members.

switch construction in the embe shown is designed to control two circuits. v n in one contact position, the auxiliary circuit for start'ng th motor is closed and remains ed until the a ature attains a predetermined. speed, which tiie the contact is broken and the switch position is reversed, effecting a contact to a close the running circuit. For example, the starting circuit may include a high voltage tap of a trmisformer, and the running circuit may include a low voltage tap of a transformer. It should be understood, however, that the particular circuit controlled by the switch is not essential to the invention and that the invention may be employed as a two-way switch or as a single make and break switch, according to the type of motor in which it is embodied.

The switch construction includes a support in the form of a plate 18, which plate 18 is attached to the inner face of the cover plate of the motor. The plate 18 is deflected inwardly so that it terminates in a plane parallel to and adjacent to the plane of the outer extremity of the sleeve 5 when the parts are in position with the motor at rest, substantially as shown in Fig. l of the drawings.

A spring plate 19 is attached to the lower extremity oi the plate 18 and extends upwardly therefrom, the upper margin of said plate 19 being unsupported. The plate 19 has a cut-out portion 20 through which the armature shaft extends. The walls of the plate 19 at the sides of the opening 20 are deflected inwardly, forming 110 shoulders 21. The cross dimension of the opening 20 is less than the diameter of the flange 6 so that, when the sleeve moves outwardly, the flange 6 contacts with the shoulders 21 and exerts pressure on the spring plate 19, holding said spring plate in substantially a vertical position. Above the upper margin of the plate 19 is a leyer-member in the form of an insulating plate 22. The plate 22 has an opening intermediate of its vertical dimension and is supported on a stud 23 that projects inwardly from the plate 18 near the upper margin thereof. The stud 23 carries an integral flange 2% at its inner end. The stud 23 extends through the opening in the plate 22, thereby providing a loose pivot for said plate. The spring 25 encircles the stud 23 and bears against the outer face of the plate 22, thereby tending to move said plate into contact with the head 24 of the stud 23. Along the lower edge of the plate 22 is an apron 26 forming a marginal channel into which the upper marginal edge of the plate 19 extends, and thereby forming a loose connection between said plate 19 and the plate 22. A contact plate 27 is connected to the upper edge of the plate 22 and is provided with contact members 28 and 29 on the opposite sides thereof. The contact plate 27 is connected with a flexible circuit lead 30.

The plate 18 has attached to its upper margin an insulating bar 31 and, to the insulating bar 31, there is attached an L-shaped bracket member 32 which carries a contact member 33 in substantial alinement with the contact member 28. On the opposite side of the contact plate 27 is a conductor bar 34 which carries av contact member 35- in substantial alinement with the contact member 29. The contact member 33 is in circuit with a lead 36, and the contact member is in circuit with a lead 3?. The circuit for the auxiliary phase winding is closed when the terminal contact member 28 contacts with the contact member 33 and, when the contact member 29 contacts with the contact member 35, the running circuit is closed.

For eficient operation of a switch of this type, it is important that the contact pressure holding the contacts of each circuit closed shall remain substantially constant until the critical speed of the motor has been attained and the transition of the switch at the critical speed initiated. Moreover, it is also important, on account of the tendency of the current through the switch to arc, that the break be accomplished rapidly and the contact points kept clean and free from surface deposits that result from the arcing at the contact points.

The switch of the present invention is highly efficient in preventing arcing and in maintaining the contact points clear of surface deposits. The manner in which these highly important results are attained will be understood from the description of the operation of the parts.

When the motor is at rest, the contact member 28 is in contact with the member 33. This closes the auxiliary phase circuit. When the armature is rotated and reaches a predetermined speed under running speed, the force tending to move the sleeve 5 inwardly toward the armature face balances the combined forces of the spiral spring '7, the spring 25 and the spring plate 19. A slight increase in speed of the armature beyond the predetermined intermediate speed causes the weighted arms of the centrifugal weight members to fly outwardly and thereby move the sleeve accuses inwardly, and thereby releases counter-pressure against the spring plate 19.

The upper end of the plate 19 thereupon moves inwardly toward the armature face, causing the lower end of the lever plate 22 to move inwardly. During this initial inward movement of the lower end of the plate 22, the plate fulcrums on the contact points 28 and 33. A continued outward movement of the lower end of the plate 22 brings the plate into contact with the head 24 of the stud 22, as illustrated in Fig. 7 of the drawings. This causes the plate 22 to fulcrum against the head 24: and to move the contact members 28 and 33 apart. When the spring i9 is in its innermost position, the plate 22 is tilted as shown in Fig. 2, effecting a contact between the contact members 29 and 35, When the motor reduces to a predetermined speed below normal running speed, the centrifugal force of the weights no longer overcomes the force of the spring 7, the sleeve moves outwardly and the flange of the sleeve again contacts with the shoulders 21 of the plate 19, forcing the plate outwardly, causing the switch member to reverse its position and again bring the contact 28 into contact with the contact 33.

By a comparison of Figs. 6 and 7, it will be noted that, when the contacts 28 and 33 break, as shown in Fig. 7, they break at the lower segment. Whatever arcing may occur would occur during the break and within the area of the lower surface of both of the contacts 28 and 33. When the contact is remade, it is made between the upper segments of the contacts 28 and 33, which are normally free from any deposit. Moreover, as the contacts assume full surface contact, there is a slight relative movement of the sur-- faces that tends to remove any deposit, keeping the surfaces clean.

The rapid break from contact position minimizes the tendency to are so that, under operating conditions, only a minimum of surface deposit on the contact faces will occur. The sliding movement between the contact members both in making and breaking is suflicient to remove this slight deposit and thereby maintain the surfaces clean.

It should also be noted that, in the operation of the device, the force holding the contacts in contact position remain substantially constant until the critical speed has been reached. When the opposing spring pressure holding the contacts in contact position is rapidly released, the parts snap into reverse position, causing a very rapid break in the contact. The-transition in position of the contact member is in the nature of a trigger action and, after the transition has been efiected, the parts interlock and are held in the alternate contact positions by adequate force to maintain a firm contact.

I am aware that the invention may be modified in numerous particulars without departing from the spirit and scope thereof. I'do not limit myself, therefore, to the exact construction shown and described, but what I claim and desire to secure by Letters Patent is:

1. In an electric motor, a switch comprising oppositely disposed stationary contacts, a pivoted member having contacts on opposite faces thereof cooperating, respectively, with said first named contacts to make and break circuits, a spring tending to move said pivoted member toward one of said stationary contacts, a spring plate operatively connected with said pivoted member and Mil ment, a spring normally actuating said switch lever toward said abutment, a spring arm for moving said switch lever in opposition to said spring when said arm is under tension and for rocking said switch lever when unrestrained, and

a centrifugally actuated device cooperatively related with the armature shaft of the motor to place said spring arm under tension when the motor is at rest and to release said spring arm when the motor has attained a predetermined speed;

3. In a motor having a stationary support and a revoluble armature shaft, the combination of a contact carried by said support, a stud carried by said support, a movable contact member loosely carried on said stud, a spring carried by said stud and operatively connected with said contact member, a plate operatively connected with said contact member, a sleeve slidably mounted on said armature shaft, a spring tending to movesaid sleeve into contact with said plate, and weighted levers operatively connected with the armature shaft and with said sleeve and adapted to move said sleeve in opposition to said last named spring and out of contact. withsaid plate.

4. In a motor having a revoluble shaft and a non-revoluble support, a fixed contact, a pivoted contact member movable toward and away from said contact, a contact carried by said contact member, a spring member for operating said piv= oted contact member having a throw inwardly of the revoluble shaft, a sleeve slidably mounted on said revoluble shaft having a free inward movement in excess of the throw of said spring member, a spring normally actuating said sleeve toward said spring member, and weighted levers cooperatively related to said sleeve for imparting to it reciprocating movement on said shaft.

5. In a motor having an armature and an armature shaft, the combination of a stationary support, a contact rigid with said support, a switch lever support carried by said stationary support, a switch lever slidably and pivotally carried by said support, a contact on said switch lever cooperating with said first named contact, means for moving said switch lever toward said first named contact, means for arresting the movement of said switch toward said first named contact, a spring arm for rocking said switch lever when said spring arm is unrestrained, and centrifugally operated means carried by the armature shaft operable to restrain said spring arm and to release said spring arm when the armature shaft has attained a predetermined speed.

6. In a motor having an armature, an armature shaft and a stationary support, a switch comprising a pair of oppositely disposed contacts carried by said support, a switch lever pivoted for movement between said supports having a spring pivot and a rigid pivot, a spring arm for operating said switch lever having a throw in the direction of the armature, a movable member supported upon the armature shaft, means for actuating said member toward the spring arm, and centrifugal weights operatively connected with said movable member and carried by the armature shaft adapted to move said movable member When the armature is under speed a distance in excess of the throw of said spring arm.

VICTOR WEBER.

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