US2333977A - Centrifugal switch - Google Patents

Description

G. W. BOWER CENTRIFUGAL SWITCH iled Sept 2, 1942 W ..W 9 W m m w $5 nr s I 6% w wirmLuo cL onumcno,

Patented Nov. 9, 1943 CENTRIFUGAL SWITCH George W. Bower, Harbor Creek, Pa., assignor to General Electric Company, a corporation of New York Application September 2, 1942, Serial No. 456,976

3 Claims.

My invention relates to centrifugally operated switches and has for its object a compact, simple and reliable device which operates with a substantial snap action.

In carrying out my invention, I provide a centrifugally operated member which is in the form of a disc and which is mounted on a rotor member of equal size driven by the actuating member. The centrifugal disc is slidably mounted for movement in a direction at right angles to the axis of the rotor member by means of a rectangular opening in the disc through which extends a rectangular guide and driving member on the rotor. The disc is furthermore cut away to provide for movement with respect to the rectangular member and whereby the disc is dynamically unbalanced and is therefore moved radially by centrifugal force. By means of springs having a very low pressure increase gradient when they are compressed by movement of the disc, 9. substantial snap action movement of the disc at a predetermined maximum speed is obtained. This disc when operated by centrifugal force engages an arm to actuate switch contacts.

For a more complete understanding of my invention, reference should be had to the accompanying drawing Fig. 1 of which is a side elevation view of a centrifugal switch embodying my invention; Fig. 2 is a frontelevation partly in section of the device shown in Fig. 1; Fig. 3 is a simplified view of the centrifugal device and switching means; while Fig. 4 is a fragmentary view showing the electrically insulating supporting block for the contacts.

Referring to the drawing, I have shown my invention in one form as comprising a stationary support l having a large central aperture Ii through the middle of which extends a shaft 12 driven by the device to whose speed the switch is responsive. Secured to the end of the shaft l2 by a suitable nut I3 is a circular rotor member M. This member I4 is provided at its outer side or end with a rectangular guiding and driving projection l5 whose center is coincident with the center line of the shaft i2 and upon which is slidably mounted a centrifugal disc member it, the disc being provided with a rectangular aperture through which the guide l5 extends.

Normally, as shown in the drawing, the centrifugal disc I6 is held by helical springs l1 and IS in peripheral registering or matching relation with the rotor 14, i. e., with the center of the disc i6 coincident with the axis of rotation of the shaft l2. It will be observed that the disc and rotor have the same peripheral size. The springs I1 and ii! are mounted in bores l9 and 20 provided for them in the guide I5. These bores are on opposite sides of the axis of the shaft and extend substantially through the guide in parallel relation with each other and at right angles with the axis of the shaft. The upper ends of the springs, as seen in Fig. 2, rest on the bottoms of these bores, while the lower ends of the springs bear on the opposite wall of the aperture in the centrifugal disc is.

To provide for movement of the disc I6, its aperture through which the guide l5 extends is enlarged on one side, i. e., the bottom side, as seen in Fig. 2, so as to be unsymmetrical and leave a space 2! at that side between the wall of the disc on which the springs l1 and I8 bear and l the guide. At the same time this enlargement of the aperture dynamically unbalances the disc, which has a uniform thickness in an axial direction, by the amount of material removed to form the space 2|. Thus, at a predetermined speed of the shaft for which the strengths of the springs and the overbalanced weight of the disc are adjusted, the dynamically unbalanced portion of the disc, i. e., the upper portion as seen in Fig. 2 moves radially outward in the plane of rotation of the disc thereby depressing the springs,

When this occurs, this unbalanced portion thrown by centrifugal force outward beyond the periphery of the rotor I4 engages a contact operating arm 22 mounted on a pivot pin 22 carried by the support III. This engagement of the arm 22, of course, is only momentary while the projecting portion of the disc passes by the contact arm. When the operating arm is moved thus counterclockwise about its pivot, as seen in Fig. 2, an armature 23 carried by it is moved into an attracted position with respect to a permanent magnet 24 mounted 0n the support 10, or the armature may be moved close enough to the magnet to provide for continued movement by the force of the magnet independently of the centrifugal disc to the fully attracted position. This movement of the arm 22 actuates electric switching means comprising three spring contact arms 25, 26 and 21. As shown, the contact arm 21 normally is in engagement at its right hand end with a stationary contact 28 thereby to maintain a circuit closed while the other two contact arms are disengaged from their stationary contacts. When operated by the centrifugal device, the contact arm 21 is moved to disengage its stationary contacts while the other two contact arms are moved into engagement with their stationary contacts.

For the operation of the contact arms, a member 29 made of electrically insulating material is secured to the end of the operating arm 22. The contact arms and 26 extend through an aperture 30 in this operating member where they are separated by an electrically insulating pin 3I. The remaining contact arm 2'! extends through a slot 32 in the member 29, Thus, movement of the operating lever 22 moves the contact arms as previously described.

At their other ends, the contact arms are secured to a projecting stud 32 on the support. As shown, the arms 25 and 26 are separated by a spacing member 33 and are secured to the projection 32 by clamping member 34 and a suitable bolt 35. In a similar manner the contact arm 21 at its other end is secured to an extension on the projection 32 by means of a clamping member 36 and a bolt 31.

For the purpose of forcibly releasing the armature 23 from the magnet, a vertically slidable button 38 is provided made of a suitable non-magnetic material, such as brass or an electrically insulating compound, and held upward in the position shown by a suitable spring (not shown). The lower end 39 of this plunger when depressed engages the armature 23 and forcibly releases it from the magnet.

Preferably, also, I provide springs I! and I8 which have the least possible pressure gradient, or at least have a pressure gradient low enough to give a substantial snap movement of the centrifugal disc to its outer position. In other words, the increased resisting pressure applied by the springs as the springs are compressed by movement of the centrifugal force acting on the disc by reason of its displaced position is more than offset by the increased centrifugal force as the disc is displaced. Therefore, the disc after starting to move is acted upon by a net increasing force which accelerates rapidly with a sudden movement. Thus, it is contemplated that this movement will be sudden enough to assure that the disc will have moved to its final position in substantially all cases before being turned around into engagement with the contact arm. However, in the event that the arm 22 is not moved upward far enough for the magnet to complete its movement by reason of the fact that the disc has not been thrown completely outward, the disc will certainly be in its ultimate position, assuming that the high speed continues, long before the next revolution of the disc has been completed. Therefore, the arm 22 will be given its movement to its final position when next engaged by the disc.

For the purpose of additionally guiding the disc I6 in its radial movement, two diametrically extending guide members 40 and 4| are provided at the top and bottom of the guide member I5, as seen in Fig, 2. These members are identical in construction and a description of one, the member 4|, will suihce for both. The member M is a rectangular plate having a rounded edge fitting in a groove 42 in the lower side, as seen in Fig. 2, of the guide I5. At its other end this member 4| has cylindrical trunnion-like projections 43 and 44 which fit respectively in apertures or recesses provided for them in the rotor I4 and a cover plate 45, This cover plate holds loosely the centrifugal disc l6 against axial displacement. It is held by four screws 46, only two of which are shown, cooperating with the corners of the rectangular guide I5. At its center the plate 45 is provided with an aperture which fits over a circular projection 41 on the guide I5,

this projection being provided with a seat for the nut I3. The thickness of the guide I5 in the direction of the axis of the shaft I2 is slightly greater than the corresponding thickness of the disc I6 so that the disc is free to move radially as previously described. Thus the guides 46 and 4|" are secured in place. Each of them fits slidably in a radial slot 48 in the disc I6 and extends parallel with the direction of movement of the disc I6.

The stationary contacts are mounted on a support 49 made of electrically insulating material, the contact being carried on suitable electrically conducting brackets which are secured to the support by bolts. Also, a projection 50 (Fig. 4) is provided on the lower end of the support to which the stationary contact 28 and its bracket are secured.

Aperture 5I are provided in the support I 6 by means of which this support can be secured to the apparatus driving the shaft I2 such as the end of an electric generator whose armature is mounted on the shaft I2.

For th purpose of assisting the magnet 24 in holding the contact arms 25 and 26 in their raised or closed circuit positions, I have provided also a spring pressed over-center toggle mechanism comprising a downwardly extending arm 52 secured to the operating arm 22 and movable about the pivot 22', On the lower end of this arm 52 is a concave cone seat 53 for the upper end of a second toggle arm 54, the lower end of which is seated in a similar cone shaped bearing 55 in a spring pressed plunger 56. A shown, the ends of the link 54 are pointed so as to form pointed bearings resting in the cone seats. The plunger 56 is mounted in a guide 51 and is biased upward by means of a helical spring 58.

In the position of the parts shown, the pivot between the links 52 and 54 is to the left of the line passing through the center of the pivot 22 and the pivot point of the link 54 on the plunger 56, and therefore the spring 58 applies a force tending to turn the arm 22 in a clockwise direction. When the arm 22 is moved upward by the centrifugal disc IS, the pivot connection between the links 52 and 54 moves to the right-hand side of this line passing through the pivot 22' and therefore reverses the torque of the spring 58 which then applies a counterclockwise force to the arm 22. This force assists the magnet 24.

While I have shown a particular embodiment of my invention, it will be understood, of course, that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

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

1. A centrifugal switch comprising a circular rotor member, a centrifugal disc having the same peripheral size as said rotor member slidably mounted on said rotor member for radial movement relative to said rotor member, said disc being dynamically unbalanced, spring means normally holding said disc in substantial peripheral matching relation with said rotor member, said spring means having a low pressure gradient thereby to provide for quick radial movement of said disc to its maximum displaced position upon the occurrence of a predetermined speed of said rotor member, and electric switch means operated by said disc.

2. A centrifugal switch comprising a circular rotor member provided with a guide projection,

a centrifugal disc of uniform thickness having the same peripheral size as said rotor member provided with an unsymmetrical aperture for said guide projection whereby said disc is dy namically unbalanced, and slidably mounted on said rotor member for radial movement relative to said rotor member, spring means normally holding said disc in peripheral matching relation with said rotor member, and electric switch means operated by said disc.

3. A centrifugal switch comprising a circular rotor member provided with a rectangular guide projection on one side having its center coincident with the center of said rotor member, a centrifugal disc having the same peripheral size as said rotor member mounted on said rotor member and having a rectangular aperture through which said guide projection extends, said aperture being larger than said guide projection on one side of said guide projection to provide for dynamic unbalance of said disc and for radial movement 01' said disc relative to said rotor member, spring means normally holding said disc in peripheral matching relation with said rotor member, and electric switch means operated by said disc upon radial movement of said disc in response to a predetermined high speed of said rotor member.

GEORGE W. BOWER.

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