US2550868A - Centrifugal switch - Google Patents

Description

J. D. RUSSELL ET AL CENTRIFUGAL SWITCH May 1, 1951 Filed Aug. 5, 1947 ggd-SMM,

Patented May 1, 1951 CENTRIFUGAL SWITCH John D. Russell and James W. Woolf, Franklin, Pa., assiguors to Joy Manufacturing Company, a corporation of Pennsylvania Application August 5, 1947, Serial No. 766,212

6 Claims.

Our invention relates to centrifugal switches, and particularly, though not in any sense limited thereto, to centrifugal switches which are very well adapted to the control of the operating circuits of motors driving belt conveyors.

In the conveying of material by belt conveyors,

-sections of great length are undesirable, and

Where a number of conveyors are arranged in series between a point or points at which material is loaded onto the first of them and a point at which discharge is desired, it is important that means be provided 'to shut down any and all conveyors ahead, in the direction of material movement, of any conveyor section which may become deranged or inoperative. Such means may advantageously employ speed responsive control devices driven from each of the conveyor sections, as, for example, by a, roller which supports the conveyor. These devices need to be simple, compact, durable, and not likely t be rendered inoperative as a consequence of substantial periods of use. Our inventionis well adapted for controls of the kind mentioned, but is not, as previously indicated, at all limited in its utility to such mechanisms.

According to our invention, in a preferred embodiment thereof, there will be provided a suitable receptacle of insulating material, preferably rotating on a vertical axis, and providing a containing chamber for mercury, and desirably sealed, and having above the level at which the mercury stands when said receptacle is at rest, pockets adapted to contain pools of mercury and to be connected, through conductors extending into said pockets in such manner as to have portions thereof constantly immersed in the mercury therein, with conductors in a circuit to be controlled. Desirably, the mercury pools may be connected with stationary contacts through suitably spaced slip rings or the like turning with the mercury containing receptacle. Desirably, moreover, the receptacle and the circuit establishing connections which are associated with it may be housed in a suitable insula'ting housing having provision for the leading of conductors into it at its lower portion, and adapted to provide protection against both moisture and breakage.

An object of our invention is to provide an improved mercury switch. Another object of to mercury contacts are made to close a circuit and in which the circuit is broken between bodies of mercury. Still another object is to provide an improved speed responsive mercury switch in which a body of mercury is adapted to be whirled in a circular, and, in a preferred embodiment, in an annular chamber having walls up which the mercury speeds upon rotation of such body, and having in said walls, at points to which the mercury attains only when whirling at a predetermined speed, pockets opening into the interior of the chamber, and each of a depth to receive and retain a pool of mercury, and connected by conductors having portions submerged in said pools and leading to annular conductors connected by brushes to stationary connector elements, said pockets being spaced appropriately to prevent arcing across between them when the circuit is broken upon reduction in rotative speed below a predetermined value. Yet a further object of our invention is to provide an improved speed controlled switch having improved protective bearing means. Other objects and advantages of our invention will hereinafter more fully appear.

In the accompanying drawings, in which one illustrative embodiment which our invention may assume in practice has been shown for purposes of illustration,

Fig. l is a central vertical sectional view through the illustrative embodiment of our irnproved centrifugal mercury switch, showing relative positions corresponding to one idle condition of the switch device;

Fig. 2 is a fragmentary view, on an enlarged scale, through the rotating, mercury-containing receptacle shown in Fig. l, with the mercury shown in the position assumed when the device is being driven at a speed suiiicient to establish and maintain a circuit; and

Fig. 3 is a horizontal section on the plane of the line 3-3 of Fig. 2, showing a detail of the mercury pool forming pockets which are t0 be connected by the mercury in the receptacle when a critical speed is exceeded.

Referring to the drawings, it may be observed that a suitable gearing-containing casing l supports, in bearings 2 and 3, a rotatable shaft 4 which is adapted to be driven by a shaft portion 5, which extends through a grease seal B to any suitable driving element, for example, a member driven from a belt conveyor. The shaft @i supports, in a compartment l forming a portion of the housing l, a relatively large bevel gear 8 which meshes with and is adapted to drive a smaller bevel gear 9 suitably carried by a shaft g metric dimension ofY the. chamber '21.

II), herein a vertical shaft, which is journaled in anti-friction bearings II and I2 carried one by a support portion I3 and the other by a septum or bracket portion I4 of the cover member l5 of the gearing casing I. Above the top of the cover member I5 there is provided an enclosure member I6 held to the cover member I5 by suitable. screws I1. The shaft I0 extends upwardly into a chamber I8 provided inside of the enclosure member I6 and, as shown, comprises, above the bearing II, an enlarged portion I 9 and a reduced portion 20 and carries, on its reduced portion, conical collar members 2| and 22, which, in cooperation with Aa nut 23 and a lock washer 24, areadapted to clamp together and secure to the shaft IU the component elements and 2S of a mercury Vchamber providing structure 21. The parts 25 and 26 are, for convenience, made essentially identical and may be formed from suitable plastic material or '-ithe like inthe. same mold or in identical molds.

Each. comprises a centrally' bored portion 23 snugly iitting around the shaft portion 29, and

Thus The shape Each of the sec- The recesses 32' anctslotsB .areshown as diametrically spaced and'thoseinthe'member 25 may be placed in overlying relation with those in the'member 2E.

Each ofthe elements 25, 2E is provided with 'an annular groove 34 in which a conducting annulus 35 may be fixed when the member is molded; and these annuli each have connected to them conductor rods 31 extending from their respective-conducting annuli to points materialy beyond the face F of the member which carries the annulus--far enough beyond to insure immersion of whichever one happens to be the 1 upper conductor rod in the mercury pool in the recess which it enters.

Stationary brackets 33 and -40 are provided for supporting brushes il and 4I respectively in position to cooperate with the-upper and lower annular conducting rings .35. Conductors 42 connected with the brushes v4may be led througha suitable conduit 43 out ofthe chamber' I81and connected in the circuit which is to` be controlled.

The mode of operation may be readily understood. The'shaft 5 will be connected through suitable 'connections (not shown) with an element whose attainment to a critical'speed it is desiredto have establish a circuit 'between the conductors 42 and whose slowing down below that speed itis desired to have open such a circuit. The gears 8 and 9 -are provided to step up the speed and thereby increase the centriflal force exerted on the mercury by the rotating compartment-forming means. After the device has once been operated, pools of mercury will stand in the-pockets 32 and be in electrical contact withv the connecting elements 31. When the'device is stationary,these pools will be separated from each other by substantially the full dia- W-hen the critical speed of rotation of the device to which the shaft 5 is connected is attained, the centrifugal force will cause the mercury, which will be whirled rapidly in the chamber 21, to assume the shape shown in Fig. 2 and to establish a circuit, through the centrifugally displaced mercury entering the pockets 32. and establishing a circuit thereby between the conductors 42, 42. If, for any reason, the speed of rotation of the shaft 8 becomes less than the critical predetermined one, the mercury will recede from the position shown in Fig. 2 towards that shown in Fig. 1, and there will be separation between a quantity of mercury in each of the pockets 32 and the mercury in the annular chamber 21. Accordingly, destruction of the connecting elements 3l will be avoided because they will not be subjected to a fusing action from the breaking of the circuits. The pockets need only be spaced suiiicientiy to prevent arcing between them. By having the rods 31 project into the pockets beyond the four sides of the orifices provided by the slots 33, no particular'carein assembly will be needed as the upper rod will thus always have its bottom immersed in mercury. The chamber 21 may desirably be sealed. The enclosure of the chamber, rings, brushes, etc. provides protection and a weather prooffconstruction. The device is obviously .simplavzdurable, certairrin operation, well prcteeted,.mid adapted to secure -mercury to mercury.- establishment of contact, and, by'separation of-A the-main mass of Vmercury from the residualpcrolsi in 'the pockets 32, protect'therods 31 When'theeircuit is broken.

While there is in' this applicationfspecically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration and that the invention maybe modied and embodied in various other forms without departing from its spirit or the` scope of the appended claims.

What we claim as new and desire to -secureby Letters Patent is:

1. A centrifugal switch including, in combination, means'forming an annulary chamber, means supporting said annular chamber-formingfmeans for rotation on an axis in the same line Wit-hA the axis of said chamber, means for rotatingsaid chamber-forming means on itsaxis, said chamber-forming means havingspaced pockets--in-yits walls, electrical contacts projecting one into-each of said pockets, stationary conductors, and' electrical connections -between said contacts :and ccnductors for maintaining `circuits between them while said chamber-forming means is rotated, and mercury in said chamberv out of contact with said pockets when said chamber-formingmeans is stationary, each of said pockets having anfindividual communication with said chamber-the low .pointof which, in,all ofthe` diierentrotated positions of said chamber-formingmeanaissubstantially above the .thenlowest pointfineaid pocket and saideelectrical contact projecting,f into Y saidpocket having a portion thereof disposed in l .saidpccket .between .such .low points, whereby a :supporting said;v annular ehambervformingg means for. rotation on, a vertical-afx is.=withthe chamber 'ffax-isin the same.;st1 =a,ight rwith-said vertical ai axis, said chamber-forming means having spaced pockets in its walls opening individually into said chamber at points each spaced from the bottom of the chamber in all of the different positions of said chamber-forming means attained by rotation upon its axis, each of said pockets having its bottom lower than the low point of its communication with the chamber, electrical contacts projecting into said pockets and each having a portion thereof below the low point of the communication with said chamber of the pocket into which it projects, mercury in said chamber below said pockets when said chamber-forming means is stationary, means for rotating said chamberforming means on said vertical axis, stationary conductors, and electrical connections between said contacts and conductors for maintaining circuits between them while said chamber-forming means is rotated.

3. A centrifugal switch including, in combination, means forming a chamber having an outer wall conforming to a surface of revolution whose axis is upright and Whose generatrix slopes outwardly and upwardly, mercury in said chamber partially filling the same, means for supporting said chamber-forming means for rotation on an axis in the same straight line with the axis of said surface of revolution, means forming pockets in said chamb-er-forming means having mouths spaced above their bottoms and opening inwardly through said outer wall at circumferentialiy spaced points in the latter and with such mouths above the static mercury level in said chamber, contact elements carried by said chamber-forming means and each having a portion extending into a pocket and to a point within such pocket below the lowest point in the mouth of the latter, stationary conductors, and means for maintaining circuits between said contact elements and said conductors while said chamber-forming means is rotated.

4. A centrifugal switch including, in combination, means forming a chamber having an outer wall conforming to a surface of revolution whose generatrix slopes outwardly and upwardly, mercury in said chamber partially filling the same, means for supporting said chamber-forming means for rotation o-n a Vertical axis, with the axis of said surface of revolution in the same straight line with said axis, means forming pockets in said chamber-forming means having mouths opening inwardly through said outer wall at circumferentially spaced points in the latter and with such mouths above the static mercury level in said chamber, contact elements carried by 6 which lies in the same straight line with the axis of the surface of revolution of said chamber, said chamber-forming means having spaced pockets in its walls opening individually into said chamber through said surface of revolution at po-ints each spaced from the low point of the chamber in all of the different positions of said chamber-forming means attained by rotation upon its axis, each of said pockets having its low point lower than the low point of its communication with the chamber in all of the different positions of said chamber-forming means attained by rotation upon its axis, mercury in said chamber, the upper surface of said mercury being lower than the low points of the communications with the chamber of said pockets when said chamber-forming means is stationary, said surface of revolution formed to cause the mercury to rise thereon on rotation of said chamber-forming means on the axis of rotation thereof, a mercury pool in each of said pockets in every position in which its respective pocket may come to rest after turning of said chamber-forming means upon its axis, means for rotating said chamberforming means on said axis of rotation to cause the mercury in said chamber to establish a connection between the mercury pools in said pockets, stationary conductors, and electrical connections between the mercury in said pockets and said conductors for maintaining circuits between the mercury in said pockets and said stationary conductors while said chamber-forming means is rotated.

6. A centrifugal switch including, in combination, a drive, rotatable means, driven by said drive, and having an internal chamber for receiving, and holding therein, a pool of mercury, and for effecting movement of the mercury, in response to operation of said drive at a predetermined speed, to cause a predetermined rise in the mercury level, said rotatable means for receiving, and holding therein, a pool of mercury also having means for providing and maintaining mutually spaced smaller pools of mercury having individual communications with said chamber spaced above their own botto-ms and Wholly above the static level of said first mercury pool and in positions to be connected with each other by the mercury of said rst pool upon a predetermined rise in the uppermost level of the mercury, stationary contacts, and means for electrically connecting said smaller pools with said stationary contacts.

JOHN D. RUSSELL. JAMES W. WOOLF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,031,893 Volk, Jr July 9, 1912 2,029,632 Moore Feb. 4, 1936 2,265,023 Bergvall Dec. 2, 1941 2,359,623 Coxon Oct. 3, 1944

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