US2418373A - Centrifugal switch - Google Patents

Description

April 1, 1947. E. T. SPALLER CENTRIFUGAL SWITCH Filed Feb. 14, 1944 5 Sheets$heet l III/1m.

April 1, 1947. SPALLER 2,418,373

CENTRIFUGAL SWITCH Filed Feb. 14, 1944 :5 Sheets-Sheet 2 INVENTOR. W 5045/? 7?" 5/ /4441 April 1, 1947.

E. T. SPALLER CENTRIFUGAL SWITCH Filed Feb. 14, 1944 sheets-sheet 3 mimvli d ll l:-

a mfl. WFJW V rN.. J m GE 5 MM v, a a m //W Arr-news Y5 Patented Apr. 1, 1947 CEN'IRIFUGAL SWITCH Elmer T. Spallcr, Cleveland Heights, Ghio, as-

signor to The Euclid Electric & Mfg. 00., Euclid, Ohio, a corporation of Ohio Application February 14, 1944, Serial No. 522,230

22 Claims. 1

This invention relates to electric switches and more particularly to an improved electric switch of the centrifugal type which is of a simple and compact construction capable of being economically manufactured.

An object of this invention is to provide an improved centrifugal switch embodying novel means for rendering such switch automatically selective in accordance with the direction of rotation.

Another object of the invention is to provide an improved switch of this character, having novel means for producing the desired actuation of the switch contacts in response to the operation of a centrifugal mechanism embodied in the switch.

A further object of my invention is to provide an improved switch of the character mentioned, in which a novel safety locking means is employed to prevent actuation of the switch contacts under certain conditions.

The invention further provides an improved centrifugal switch of this character in which auxiliary contacts embodied in the safety means control the energization of the circuit containing the centrifugally actuated contacts.

The centrifugal switch herein disclosed is an improvement over the switch mechanism of Patent No. 2,136,252, dated November 8, 1938.

In the accompanying sheets of drawings,

Fig. 1 is a side view with portions in section showing a centrifugal electric switch embodying my invention;

Fig. 2 is a transverse sectional View of the device taken on line 2-2 of Fig. 1;

Fig. 3 is a partial sectional view with the switch contacts and their supporting means shown in elevation, the latter being viewed as indicated by line 3-3 of Fig. 2;

Fig. 4 is a partial plan view showing the contact actuating means when viewed as indicated by line 4-4 of Fig. 3;

Fig. 5 is a partial plan view similar to Fig. 4 but showing the different positions to which the contact actuating arm is movable;

Fig. 6 is a diagrammatic View further illustrating the centrifugal switch of Figs. 1 to 5 inclusive and its use in a motor control circuit;

Fig. '7 is a partial plan view showing a modified form of my centrifugal switch;

Fig. 3 is a transverse sectional view of the modified switch taken substantially on line 8-43 I Proceeding now with a more detailed description of the present embodiment of the invention, I show my improved switch as having a frame is provided with end walls Ilia and I01) in which a shaft ii is rotatably mounted by means of anti-friction bearings I2 and E3. The shaft II is adapted to be connected with an electric motor or other electric apparatus with which my improved switch is used. The switch also embodies a centrifugal mechanism M which rotates with the shaft I! and performs two functions, the first of which is to automatically select or preselect the contacts to be actuated, in accordance with the direction of rotation of the shaft I l and the r other of which is to actuate such selected contacts to cause closing or opening of a desired circuit in response to a predetermined change in the speed of rotation of the shaft. My improved switch may at times be referred to as a zero speed switch, a plugging switch or a pilot circuit switch.

The centrifugal device l4 comprises a yoke [5 connected with the shaft I l and a pair of weights I6 pivotally mounted on the divergent arms I! of such yoke. The weights I6 are pivotally connected to links it by which they are connected with a sleeve is which is mounted on the shaft H and is axially shiftable thereon. The sleeve 19 carries an anti-friction bearing 20 on which is mounted a hollow body 2| carrying a substantially radially projecting finger 22. The bearing 2t is retained on the sleeve Is as by means of a snap ring 23 engaging in an annular groove provided in such sleeve adjacent the inner end thereof. The finger 22 is constructed with a slotted body portion 22a which surrounds or straddles the shaft H and is connected with the hollow body 2| by means of the screws 24 and 25 and the spacers 24a provided on the latter. A compression spring 26 disposed around the screw 25 engages the body portion 22a of the finger 22 so as to yieldably hold the same against the spacers 24a.

ifhe outer end of the sleeve it, that is the end thereof nearest the centrifugal mechanism l4, carries a pair of spring pressed plungers 28 whose inner ends are in frictional sliding engagement with the adjacent annular face 2t of the body 2|. The friction plungers 23 can be made of any suitable material or composition and are slidable in hollow radial portions or lobes [9a of the sleeve ill so that compression springs 39 acting against such plungers will hold their inner ends in frictional engagement with the face 29 of the body 2!. The outer ends of the springs 35 engage in cup-shaped members 3| which seat against cotter pins 32. A compression spring 33 disposed around the shaft l I between the inner end of the yoke l5 and the outer end of the sleeve 19 normally urges the sleeve away from the yoke so as to exert a pull on the links l3 which urges the Weights I5 toward their retracted or zero speed position in which they are shown in full lines in Fig. l.

From the description of my improved switch as thus far given, it will be seen that the centrifugal mechanism l4 and the sleeve i9 both rotate with the shaft H and that the sleeve will be slidably moved axially of the shaft by the expansion and retraction of the centrifugal weights l6. Such axial sliding movements of the sleeve l9 will cause corresponding axial movements of the body 2| and the finger 22 carried thereby. It will also be seen that the friction plungers 28 engaging the end face 29 of the body 2| will provide a drag between the sleeve l9 and body such that the initial rotation of the shaft 1 I will cause the body 2i to rotate with the sleeve. This frictional drag forms a yieldable connection by which the body it can be rotated or arcuately shifted through a limited distance for the purpose of moving the finger 22 to one or the other of its contact selecting positions 22b and 22c which are shown in broken lines in Fig, 2, The direction in which the finger 22 is shifted is dependent upon the direction of rotation of the shaft 1 l and when the finger has been thus shifted to its contact-selecting position the friction plungers 28 slide on the face 28 of the body 2|.

The yieldable finger 22 cooperates with a contact-actuating arm 35 which is mounted on a fulcrum or pivot 36 carried by a support 37. One end of the arm 35 carries a body 38 formed of insulating material which cooperates with a movable contact or switch member 39 so as to shift the same with respect to a pair of stationary contacts 4H and 4|. When the rotation of the shaft H reaches a speed sufficient to cause expansion of the weights [5, the sleeve 19 is pulled toward the centrifugal mechanism causing the finger 22 to engage the arm 35 and swing the same on its pivot and thus shift the movable contact 39.

The movable contact 39 is here shown as being in the form of a resilient arm or leaf spring having its lower end substantially rigidly attached to a terminal member 42. Its upper end carries a rounded portion 43 forming an anti-friction hearing which engages in a recess 38a of the insulating body 38. The movable contact 39 is pro- Vided at an intermediate portion thereof with contact points 44 and 4-5 which cooperate respectively with the stationary contacts 40 and 4| so that elements 40 and 44 constitute one pair of cooperating contacts and the elements 41 and 45 constitute another pair of cooperating contacts. The stationary contacts 40 and 4| are carried by terminal members 46 and 4'! in which they are mounted for adjustment with respect to the movable contact 39. The terminal members 42, 48 and 4! are all carried by an insulating panel 48 which is connected with the support 3'].

In Figs. 3 and 4 of the drawings I show the contact-actuating arm 35 in a central position, in which both pairs of switch contacts are open. The arm 35 is urged toward such a central position by the tension spring 53 disposed around the pivot 36 and having a pair of projecting ends 50a and 53b lying on opposite sides of, and acting against, a depending pin 5| carried by such arm. The spring ends 59a and 551) also straddle a stationary pin or stop 52 carried by the support 3?. Whenever the arm 35 is swung from its central position as indicated in Fig. 4, the spring 50 is stressed and, depending upon the direction in which the arm is swung, one or the other of the 4 spring ends 53a and 5% acts on the depending pin 51 tending to return the arm to its central position.

In Fig. 5 I show the yieldable selecting finger 22 as having been shifted arcuately by an initial clockwise rotation of the shaft H to a position at one side of the pivot 36, and also as having been shifted axially of the shaft II by the centrifugal mechanism H to engage and swing the arm 35, Fig. 5 shows the arm 35 in full lines as having been swung in a direction to cause closing of the contacts 49 and 44. When the shaft ii is initially rotated in the opposite direction, that is in a counter-clockwise direction as seen in Fig, 5, the finger 22 is shifted to the broken line position 2222 and the subsequent axial movement of the finger 2'2 by the centrifugal device I4 swings the arm 35 to its broken line position causing closing of the contacts 4| and 45.

With the construction and arrangement above described, it will be understood, or" course, that when the shaft ll slows down to a predetermined speed or ceases to rotate, the spring 33 shifts the sleeve is away from the centrifugal mechanism l4 thereby disengaging the finger 22 from the arm 35 and permitting the latter to be returned to its central position by the spring 50 and that this movement of the arm 35 returns the movable contact 39 to its initial position. The above mentioned adjustment for the contacts and M permits either of these contacts to be adjusted to a position such that it will be engaged by the contact 39 when the latter is in its initial position.

improved switch embodies a safety means 5:1 by which the contact-actuating arm 35 can be locked against movement so that actuation of the switch contacts can be prevented during certain conditions. It is desirable to prevent actuation of the switch contacts at certain times such as when the machinery with which my switch is being used is being turned over by hand for purposes of setting up or inspecting the work on which such machine is to operate. If the switch contacts were not prevented from closing during such preliminary operations, the turning over of the machine by hand might cause rotation of the shaft H at a speed sufficient to cause closing of the switch contacts and this would result in energization of electric apparatus which might cause personal injury.

The safety means 54 shown in this instance comprises a magnet or relay 55 having a frame or stator 56 mounted on the support 31, and a movable armature 58 which is responsive to the energization of the winding 59 of such magnet. The free end of the armature 58 is provided with a slot 58a which straddles an abutment pin or stop carried by the support 31. The adjacent end of the contact-actuating arm 35 carries a depending pin 6| which engages in the slot 58a when this arm is in its central position. The engagement of the depending pin 6| in the slot 58a holds or locks the arm 35 in its central position until the armature 58 is pulled down by energization of the coil 59 at which time the armature releases the pin 6! to permit swinging of the arm 35 by the finger 22. The coil 59 of the magnet is suitably connected with the electric apparatus with which my switch is used so that, as soon as the control switch is actuated to start such apparatus, the magnet 55 will be energized to release or unlock the arm 35.

During the period of time that the arm 35 is held in one or the other of its contact-closing positionsby the finger 22, the depending pin 61 of this arm overlies the armature 58 of the relay 54 as shown in Fig. 5 and holds the armature in a depressed position. When the arm 35 is returned to its central position the free end of the pin 6| slides over the face of the armature and drops into the slot 58a to establish the abovedescribed locked condition.

As shown in the drawings the support 3'! which carries the panel 63 and the relay 55 is adjustably connected with the frame If! by means of the bracket 62 and the clamping screws 63 which extend through the slots fi ler the support. By adjusting the position of the support 37 axially of the device and relative to the finger 22 the timing of the closing and opening of the switch contacts can be varied or adjusted with respect to the speed of rotation of the shaft 1 I.

In the diagrammatic view of Fig. 6 I show my centrifugal switch connected with the shaft of an electric motor 63 and being used as a plugging switch for this motor. In this diagram the conductors Li, L2 and L3 are the line conductors for the motor and contain a reversing switch B-i having forward and reverse contacts F and R. A pair of forward and reverse push button switches 65 and 66 control the energization of magnets 67 and t3 which actuate the main switch ii and also actuate the auxiliary contacts f and r. As shown in thi diagram the contacts 35, is and M of the centrifugal switch control the plugging circuit but are prevented from closing by the locking relay 5 3 until the magnet 55 of the relay is energized and this does not occur until energization of the motor 63 is desired and one of the push button switches is closed for this purpose.

Figs. 7 to 9 inclusive show a modified form of my centrifugal switch in which the safety means embodies an auxiliary switch iii which controls the energization of the circuit containing the centrifugally actuated contacts. In all other respects the switch of Figs. '7 to 9 inclusive is identical wi h the switch of Figs. 1 to 5 inclusive and the same reference characters have been used on corresponding parts. The diagram of Fig. 10 includes the auxiliary switch it and applies to Figs. 7 to 9 inclusive in substantially the same way that the diagram of Fig. 6 applies to Figs. 1 to 5 inclusive.

In the modified centrifugal switch of Figs. '7 to 9 inclusive the auxiliary switch it comprises stationary contacts El and 12 located in the circuit portion 13 leading to the movable or leaf contact 39 and a movable contact M which cooperates with the stationary contacts i and 12 and is carried by the armature 58 of the relay E i. The contact I is insulated from the armature by being extended through an insulating body 74a which is riveted to the armature. With the safety means illustrated in Figs. '7 to 10 inclusive it will be seen that the, contact 39 is deenergized at the switch it and that the latter will be closed only when the magnet 55 of the relay 55 is energized by energization of the motor 63. The mechanical action of the depending pin 6! of the arm 35 in holding the armature 58 of the relay in its depressed position maintains the auxiliary switch l8 closed during the transition period, that is, the fraction of a second during which the forward and reverse contactors 61 and 68 are shifted and the plugging operation is being initiated.

In the modified switch shown in Figs. 7 to 9 inclusive the feature of mechanically locking the contact-actuating arm 35 in its central position isless important because when this arm is in its central or initial position the auxiliary switch 10 will be. open. Therefore when the safety means includes the auxiliary switch Hi, the abutment pin 60 can be omitted and the slot of the armature 58 can be made relatively wide as indicated at 58b in Fig. 10.. As mentioned above, the depending pin El cooperates with the armature 58 in holding the auxiliary switch iii closed during the. transition period but when the wide slot 58b is used this pin does not lock the arm 35 in its central position. In Fig. 10 the reference character 53c designates the armature portion which is engaged by the pin ill for holding the auxiliary switch closed during the transition period.

From the foregoing description and the accompanying drawings, it will now be apparent that I have provided an improved centrifugal switch which is of a very simple and compact construction. It will be seen also that through the frictional slip connection between the centrifugal mechanism and the mounting for the actuating finger, the switch is rendered auto matically selective in response to the direction of shaft rotation. Likewise it will now be apparent that the switch embodies simple and direct means for actuating the switch contacts in response to a predetermined speed of rotation for the centrifugal mechanism. It will also be apparent that the novel safety means embodied in my switch will prevent actuation or energization of the switch contacts under conditions or circumstances which might result in personal inury.

While I have illustrated and described my improved. centrifugal switch in considerable detail it will be understood, of course, that I do not wish to be correspondingly limited but regard my invention as including all changes and modifications coming within the spirit of the invention and the scope of the appended claims.

Having thus described my invention, I claim:

1. In a centrifugal switch, a shaft adapted to be rotated in either a forward or reverse direction, a centrifugal mechanism rotatable with said shaft, a plurality of cooperating switch contacts comprising a pair of spaced stationary contacts and a movable contact therebetween, and means for causing engagement of one of said stationary contacts by said movable contact including a yieldable finger projecting substantially radially from said shaft and adapted to be shifted by said mechanism.

2. In a centrifugal switch, a shaft adapted to be rotated in either a forward or reverse direction, a centrifugally responsive mechanism rotatable with said shaft, a plurality of cooperating switch contacts comprising a pair of spaced stationary contacts and a movable contact disposed thereb-etween, means for causing actuation of said movable contact for engaging the same with one of said stationary contacts in accordance with the direction of rotation of said shaft including a finger extending substantially radially of said shaft. means rockable and slidable relative to the shaft and mounting said finger for shifting both arcuately and axially of said shaft, and means for causing such arcuate and axial shifting of said finger mounting means in response to rotation of said centrifugally responsive mechanism in either direction.

3. In a centrifugal switch, a shaft adapted to be rotated in either a forward or reverse direction, a centrifugal mechanism rotatable with said shaft, a plurality of cooperating switch contacts, means for causing actuation of said contacts including a finger extending substantially radially of said shaft, means mounting said finger for shifting both arcuately and axially of said shaft, the arcuate shifting of said finger being in either of two directions corresponding with the directional rotation of said shaft, means connecting said mounting means with said mechanism so as to cause said finger to be shifted axially of said shaft in response to rotation of said mechanism, and friction means for causing an initial arcuate shifting of said finger in response to the direction of shaft rotation.

4. In a centrifugal switch, a shaft adapted to be rotated in either a forward or reverse direction, a centrifugal mechanism rotatable with said shaft, a plurality of cooperating switch contacts, a contact-actuating arm mounted for swinging movement, a. finger extending substantially radially of said shaft, means mounting said finger on said shaft so as to be shiftable to a preliminary position by arcuate movement about said shaft in either of two directions corresponding with the directional rotation of said shaft and permitting said finger to also be shifted axially of the shaft for causing swinging of said arm, and means operably connecting said mechanism with said finger mounting means for causing such arcuate and axial shifting of said finger in response to rotation of said mechanism.

5. In a centrifugal switch, a rotary shaft, a centrifugal mechanism rotatable with said shaft, a plurality of pairs of cooperating switch contacts, a contact-actuating arm mounted for swinging movement such that swinging in one direction actuates one pair of said contacts and swinging in the opposite direction actuates another pair of said contacts, a finger extending substantially radially of said shaft, means mounting said finger for shifting both arcuately and axially of said shaft, the axial shifting of said finger causing the same to swing said arm, and means for causing such arcuate and axial shifting in r sponse to rotation of said centrifugal mechanism.

6. In a switch of the character described, a rotatable shaft, a fiyweight mechanism rotatable with said shaft, a sleeve movable axially on said shaft and connected with said mechanism for actuation thereby, a movable switch member, pairs of cooperating contacts adapted to be selectively actuated by switch member, an arm mounted for swinging movement and having an operating connection with said switch member such that swinging of said arm in one direction actuates one pair of said contacts and swinging of said arm in the other direction actuates another pair of contacts, and means adapted to be shifted in accordance with the direction of rotation of said shaft and movable axially with said sleeve to cause swinging of said arm.

'7. In a switch of the character described, a rotatable shaft, a fiyweight mechanism rotatable with said shaft, a sleeve movable axially on said shaft and connected with said mechanism for actuation thereby, a movable switch member, pairs of cooperating contacts adapted to be selectively actuated by said switch member, an arm mounted for swinging movement and having an operating connection with said switch member such that swinging of said arm in one direction from a central position actuates one pair of said contacts and swinging of said arm in the other direction from said central position actuates another pair of said contacts, a spring acting on said arm and tending to return the same to said central position, and means adapted to be shifted in accordance with the direction of rotation of said shaft and movable axially with said sleeve to cause swinging of said arm.

8. In a centrifugal switch, a rotatable shaft, 21 fiyweight mechanism rotatable with said shaft, an arm mounted for swinging movement, cooperating switch contacts adapted to be actuated by such swinging movement of said arm, means connected with said flyweight mechanism and movable thereby axially of said shaft for imparting said swinging movement to said arm, and locking means cooperating with said arm and adapted to be released to permit swinging thereof.

9. In a centrifugal switch, a rotatable shaft, 9, fiyweight mechanism rotatable with said shaft, an arm mounted for swinging movement, cooperating switch contacts adapted to be actuated by such swinging movement of said arm, means connected with said flyweight mechanism and movable thereby axially of said shaft for imparting said swinging movement to said arm, and electromagnetic locking means cooperating with said arm and adapted to be energized to release said arm for swinging movement.

10. In a switch of the character described, a rotatable shaft, a fiyweight mechanism rotatable with said shaft, a sleeve movable axially on said shaft and connected with said mechanism for actuation thereby, a movable switch member, pairs of cooperating contacts adapted to be selectively actuated by said switch member, an arm mounted for swinging movement and having an operating connection with said switch member such that swinging of said arm in one direction actuates one pair of said contacts and swinging of said arm in the other direction actuates another pair of said contacts, means adapted to be shifted in accordance with the direction of rotation of said shaft and movable axially with said sleeve to cause swinging of said arm, and locking means cooperating with said arm and adapted to be released to permit swinging thereof.

11. In a switch of the character described, a rotatable shaft, a flyweight mechanism rotatable with said shaft, a sleeve movable axially on said shaft and connected with said mechanism for actuation thereby, a movable switch member, pairs of cooperating contacts adapted to be selectively actuated by said switch member, an arm mounted for swinging movement and having an operating connection with said switch member such that swinging of said arm in one direction actuates one pair of said contacts and swinging of said arm in the other direction actuates another pair of said contacts, means adapted to be shifted in accordance with th direction of rotation of said shaft and movable axially with said sleeve to cause swingin of said arm, and electromagnetic locking means cooperating with said arm and adapted to be energized to release said arm for swinging movement.

12. In a centrifugal switch, a rotary shaft, 9. centrifugally responsive mechanism rotatable with said shaft, a plurality of cooperating switch contacts, a contact-actuating arm having a central position and being pivoted for swinging movement in either direction from said central position, spring means urging said arm toward said central position, a finger extending substantially radially of said shaft, means mounting said finger for shifting axially of said shaft for engaging and swinging said am, said mounting means being such as to permit arcuate shifting of said finger from one side of the arm pivot to the other, and means connecting said mounting means with said mechanism so as to cause such arcuate and axial shifting of said finger in response to rotation of said mechanism.

13. In a centrifugal switch, a rotary shaft, a centrifugally responsive mechanism rotatable with said shaft, a plurality of cooperating switch contacts, a contact-actuating arm having a central position and being pivoted for swinging movement in either direction from said central position, spring means urging said arm toward said central position, a finger extending substantially radially of said shaft, means mounting said finger for shifting axially of said shaft for engaging and swinging said arm, said mounting means being such as to permit arcuate shiftin of said finger from one side of the arm pivot to the other, means connecting said mounting means with said mechanism so as to cause such axial shifting of said finger in response to rotation of said mechanism, and friction means embodied in said connecting means for causing such arcuate shifting of said finger in accordance with the direction of shaft rotation.

14. In a centrifugal switch, a rotary shaft a centrifugally responsive mechanism rotatable with said shaft, a plurality of pairs of cooperating switch contacts, a contact-actuating arm mounted for swinging movement such that swinging in one direction actuates one Pair of said contacts and swinging in the opposite direction actuates another pair of said contacts, a finger extending substantially radially of said shaft, means mounting said finger for shifting both arcuately and axially of said shaft, the axial shifting of said finger causing the same to swing said arm, means for causing such arcuate and axial shifting of said finger in response to rotation of said centrifugal mechanism, and locking means cooperating with said arm and adapted to be released to permit swinging thereof.

15. In a centrifugal switch, a rotary shaft, a centrifugally responsive mechanism rotatable with said shaft, a plurality of pairs of cooperating switch contacts, a contact-actuating arm mounted for swinging movement such that swinging in one direction actuates one pair of said contacts and swinging in the opposite direction actuates another pair of said contacts, a

said arm, means for causing such arcuate and axial shifting of said finger in response to rotation of said centrifugal mechanism, and electromagnetic locking means cooperating with said arm and adapted to be energized to release said arm for swinging movement.

16. A centrifugal switch as defined in claim 6, in which said switch contacts and pivoted arm are carried by a support which is adjustably movable axially of said shaft.

17. A centrifugal switch as defined in claim 10, in which said switch contacts, pivoted arm and locking means are carried by a common support which is adjustably movable axially of said shaft.

18. In a centrifugal switch, a rotatable shaft, cooperating switch contacts, means responsive to the direction and speed of rotation of said shaft for actuating said switch contacts, locking means for preventing such actuation of said switch contacts, and electromagnetic means for rendering said locking means ineffective.

19. In a centrifugal switch, a rotatable shaft, cooperating switch contacts, means responsive to the direction and speed of rotation of said shaft for actuating said switch contacts, normally open auxiliary switch contacts electrically connected with the first mentioned switch contacts for controlling the energization of the latter, and electromagnetic means for closing said auxiliary switch contacts.

20. In a centrifugal switch, a rotatable shaft, cooperating switch contacts, means responsive to the direction and speed of rotation of said shaft and movable to a predetermined position for actuating said switch contacts, normally open auxiliary switch contacts electrically connected with the first-mentioned switch contacts for controlling the energization of the latter, electromagnetic means adapted to be energized for closing said auxiliary contacts, and mechanical means for maintaining said auxiliary contacts closed while the first mentioned means is in said predetermined position.

21. In a centrifugal switch, a rotatable shaft,

a flyweight mechanism rotatable with said shaft,

an arm mounted for swinging movement from an initial position to a predetermined position, cooperating switch contacts adapted to be actuated by such movement of said arm to said predetermined position, means connected with said flyweight mechanism and movable thereby axially of said shaft for imparting said swinging movement to said arm, normally open auxiliary contacts electrically connected in series with the first mentioned contacts, electromagnetic means for closing said auxiliary contacts, and mechanical means enabling said arm to hold said auxiliary contacts closed while said arm is in said predetermined position, said mechanical means being ineffective while said arm is in said initial position.

22. In a centrifugal switch, a rotatable shaft, a fiyweight mechanism rotatable with said shaft, an arm mounted for swinging movement in either direction from an initial position to one or the other of predetermined positions located on opposite sides of said initial position, cooperating switch contacts adapted to be actuated by such movement of said arm to either of said predetermined positions, means connected with said flyweight mechanism and movable thereby axially of said shaft for imparting said swinging movement to said arm, normally open auxiliary contacts electrically connected in series with the first mentioned contacts, electromagnetic means for closing said auxiliary contacts, and mechanical means enabling said arm to hold said auxiliary contacts closed while said arm is in either of said predetermined positions, said mechanical means Number Name Date 2,282,366 Knight May 12, 1942 1,534,025 Brinton Apr. 21, 1925

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