US2880287A - Centrifugal switch - Google Patents

Description

March 31, 1959 J. JANES CENTRIFUGAL SWITCH 2 Sheets-Sheet 1 Filed Dec. 24, 1956 INVENTOR. JOSEPH J/a -55 FIG 5 March 31, 1959 J. JANES CENTRIFUGAL SWITCH 2 Sheets-Sheet 2 Filed Dec. 24, 1956 INVENTOR. JOSEPH Jmwzs BY United States Patent CENTRIFUGAL SWITCH Joseph Janes, Arlington, Mass.

Application December 24, 1956, Serial No. 630,115

1 Claim. (Cl. 200-80) This invention relates to electrical switches of the type operable in response to centrifugal force and used, for example, on rotating shafts for various control purposes.

The general object of this invention is to provide a centrifugal switch which is simple in construction, durable, positive in action, and suitable for installation on either new or existing equipment. In one form of the switch a number of balls are confined between a pair of shells which have opposed bevelled surfaces. One shell is fixed to the shaft and the other shell is axially movable along the shaft. The movable shell is springpressed toward the fixed shell. Under centrifugal force, the balls engage the bevelled surfaces and push the shells apart, and the movement of the movable shell causes opening or closing of electrical contacts.

In another form, the switch consists, in general, of a spider, which is designed to be mounted on a shaft and has a number of radial recesses in which a number of balls are freely received, a stationary casing surrounding the spider, and a hinged arm which is engaged by the balls when they fly outward under centrifugal force and which, in turn, opens or closes electrical contacts.

Other advantages and novel features of the invention will be apparent from the following description.

In the drawings illustrating the invention:

Fig. 1 is a plan view of an electric motor with its housing partly broken away, on which a switch, made according to the invention, is installed;

Fig. 2 is a cross-section taken along line 2-2 of Fig. 1;

Fig. 3 is a cross-section taken along line 3-3 of Fig. 1.

Fig. 4 is a cross-section taken along line 4-4 of Fig. 2, the switch being shown in running position;

Fig. 5 is a schematic drawing of an example of motor control circuit which may be controlled by means of the switch;

Fig. 6 is a plan view of an electric motor, with its housing partly broken away, on which a modified form of the switch is installed;

P Fig. 7 is a cross-section taken along line 7-7 of Fig. 8 is a cross-section taken along line 8-8 of Fig. 7; and

Fig. 9 is a cross section taken along line 9-9 of Fig. 6, the switch being shown in running position.

In the form of switch illustrated in Figs. 1-5, the working parts are mounted on a tubular collar 10 which is fixed to the shaft 11 of the motor 12. A circular shell 13, having an internal circular bevelled face 13a, is fixed to collar 10. The collar and shell 13 may, for example, be secured together and to the shaft by means of a set screw 14. A second shell 15 is slidably mounted on collar 10 and has an internal circular bevelled face 15a which opposes face 13a. A ring-shaped plate 16 is slidably mounted on collar 10 and is connected to shell 15 by a number of shouldered rivets 18 which are 2,880,287 Patented Mar. 31, 1959 fixed in the plate and shell 15 and pass freely through shell 13. The latter has a number of recesses 17 in which coil springs 19, encircling rivets 18, are seated. These springs urge plate 16 to the left and thus hold shell 15 against shell 13, as shown in Fig. 1, when the shaft is standing still.

A number of balls 20, made of steel, or some other fairly heavy material, are disposed between shells 13 and 15. Shell 15 has an internal flange 15b which forms a seat limiting the inward travel of the balls when the motor is stopped, as seen most plainly in Fig. 2.

A fixed insulating plate 21 is mounted in any convenient manner to the left of, and spaced away from, plate 16. Collar 10 passes freely through plate 21. Mounted on plate 21 are two contact brackets 22 and 23 carrying fixed contacts 24 and 25, respectively. A bowed, ring-shaped leaf spring 26 is attached to plate 21 at the bottom, and carries a pair of contacts 27, 28 which may engage with contacts 24 and 25, respectively. The spring 26 is biased so that contact 28 would normally engage contact 25.

The operation of the switch is as follows:

When the motor shaft is standing still, spring 19 presses plate 16 against spring 26, thus holding contact 27 in engagement with contact 24. When the motor starts to run, balls 20 fly outward against the bevelled surfaces 13a and 15a and force shell 15 to the right, away from shell 13. Plate 16, being attached to shell 15, is carried to the right out of engagement with spring 26, and the latter springs over to its normal position, bringing contact 28 into engagement with contact 25. If the motor stops, springs 19 will return plate 16 and shell 15 to the position shown in Fig. 1 as the balls,

when relieved of centrifugal force, are readily pushed inward by the pressure of surfaces 13a, 15a. It is thus apparent that, when the shaft is standing still, contacts 24, 27 will be closed and contacts 25, 28 open, and when the motor is running, contacts 24, 27 will be open and contacts 25, 28 closed.

A motor control circuit, which may be operated by means of the switch, is shown in Fig. 5. The motor is represented as having an armature 30, a primary or running coil 31, and a secondary or starting coil 32. Contact 24 is connected in the energizing circuit of secondary 32, and contact 25 is connected in parallel with a starter button 33 in the energizing circuit of primary 31. Leaf spring 26 is schematically shown in full line in the running position and in dotted line in the standing position. With this arrangement, when the motor is standing still, and contacts 24, 27 closed, a circuit will be established through both coils 31 and 32 when the starter button 33 is depressed. When the motor is running, contacts 24, 27 will open, cutting out coil 32, and contacts 25, 28 will close, shunting button 33 and establishing a holding circuit through coil 31. If the motor stops because of an overload, for example, the switch will open contacts 25, 28, cutting out the primary coil, and close contacts 24, 27, putting the system back into condition to be started by button 33.

In the form of switch shown in Figs. 6 to 9, a spider member 40 is fixed to the shaft 11, for example by means of a set screw 39. The spider is rotatable within a housing 41 which is stationary and may be mounted in any convenient manner, for example, by attaching it to the housing 12 of the motor. The spider has a number of radial recesses 42 disposed around its periphery. A number of balls 43 ride loosely in these recesses, and can move outward under centrifugal force until they engage housing 41.

Mounted in housing 41 is an arm 44 which is rotatable about pin 45. A second pin 46 serves as a stop to limit the movement of arm 44 away from the shaft. arm has an arcuate inner cam surface 44a.

A contact assembly consisting of leaf springs 47, 48 and 49, separated by insulating blocks 50, is mounted on housing 41. Springs 47 and 49 carry contacts 51 and 52-, respectively, and spring 48' carries contacts 53 and 54. Spring 48 is biased so that contact 53 normally engages contact 51. Arm 44 carries a stud 55 which can engage spring 48, when the arm swings out, and bend this spring to bring contact 54' into engagement with contact 52.

When the motor is stopped, arm 44 is held by spring 48 in the position shown in Fig. 7. Contacts 51, 53 are closed and contacts 52, 54 open. When the motor starts to run, balls 43 fly outward, to the limit permitted by housing 41, under centrifugal force. As spider 40 is. rotating, and housing 41. along with arm 44 is stationary, the balls successively engage cam surface 44a, causing a to rotate outward about pin 45 to the limit permitted by's't'o'p "46. Stud SS-pushes spring 43- upward (as seen in Fig; 9) opening contacts 51, 53 and closing contacts 52, 54. Thisform of-switch mayoperate the control circuit shown in Fig. 5, contacts 51, 53 being connected in place of contacts 24, 27, and contacts 52, 54 in place of contacts 25, 28.

The form of switch shown in Figs 6 to 9 is unidirectional, that is, intended to operate with the shaft running clockwise, as viewed in Fig. 9. For operation in the opposite direction, the switch must be reversed on the shaft. the same manner for either direction of shaft rotation and is thus suitable for reversible motors.

It will be understood that the contact arrangement on either type of switch can be varied to provide a single contact either normally open or normally closed, or any desired arrangement of multiple normally open or normally closed contacts.

The switch is made of a small: number of parts, is durable, and requires no fine adjustment, lubrication, or other servicing in operation.

The

The switch shown in Figs. 1 to 4 operates in What is claimed is:

A centrifugal switch comprising a tubular sleeve adapted to be mounted on a rotating shaft, a pair of ring-shaped shells, one of which is fixed to said sleeve and the other of which is movable axially along said sleeve, a ring-shaped plate surrounding and movable axially along said sleeve, the fixed shell being disposed between said plate and the movable shell, a plurality of studs connecting said plate to the movable shell, said studs passing freely through said fixed shell and securing said plate and the movable shell against rotation with respect to the fixed shell, a plurality of compression springs, one encircling each of said studs and bearing on said fixed shell and said plate, a number of balls loosely confined between said shells and movable radially outward from said sleeve under centrifugal force, said shells having opposed ring-shaped interior outwardly converging bevelled faces engageable by said balls when the latter move outward, a ring shaped contact mernher surrounding said sleeve, said member having bowed portions slidably engaged with said plate when said balls are in their innermost position, an insulating member connected to said contact member, and a pair of contacts, one mounted on said contact member and the other on said insulating member, said contacts being adapted to be engaged and disengaged by movement of said plate.

References Cited in the file of this patent UNlTED STATES PATENTS 848,292 Dawson Mar. 26, 1907 1,106,092 Guild Aug. 4, 1914 1,698,322 Stobe Jan. 8, 1929 1,910,245 Harrelson May 23, 1933 1,976,925 Chryst Oct. 16, 1934 2,273,963 Jereczek Feb. 24, 1942 2,598,481 Young May 27, 1952 2,779,837 Gardes Jan. 29, 1957

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