US956221A - Magnetic tachometer. - Google Patents

Description

J. K. STEWART.

MAGHTIC TAGHOYETER.

Pulau iss FILED Nov. 1s, was.

Patented Apr. 26, 1910.

20 'index finger being caused by lthe magnetic "-'AUNITED STATES PATENT orales.

i Y JOHN x. STEWART, or omesso, ILLINOIS.

Y MAGNETIC TAcHoMErrin.

To all whom it may concern:

Be it known that I, JOHN K. STEWART, a citizen of the United States, residing at, Chicago, in the county of Cook and State fi of Illinois, have invented new and useful Improvements in Magnetic Tachometers, of which the' following is a specification, reference beingr had to the drawings forming a part thereof. f Y This invention relates to theV class of speed-measuring devicesv in which there are associated -three elements, a magnet, its armature and-a third element of low magnetic resistance interposed in the magnetic I' ld, one of the three elements being rotated, and a second having an indicating device, as an index finger, and being mounted for oscillation aganst a yieldingT resist- 'ance or biasing means, the deflection of the drag of the rotating element upon the oscillating element.

It consists in the features of construction and their'. combination shown and described as indicated in the claims.

In the drawings :-F igure l is a face View of a tachometer embodying this invention, the dial plate and armature disk bein; r each in part broken away to disclose their ele- U ments.' Fig. 2' is an' axial section of the v ,Y ed the dia-l plate. 13, which is preferably protected by a glass, C. At the center of 0 the case', rigid with the. yback `or bottom disk, 1. thereof, there is `erected, preferably formed integrally with rthe case, a post, 2. This post.Y is reduced in diameter at Aits upper part, forming an inclined shoulder. 3, which 5 constitutesv the ball seat of' a ball bearing, -indicated by the balls, D, and about the reduced [Ent there is journaled the magnet' element. As illustrated, the magnetelemerit, E, comprises a central iron or steel 0 member, EL, unmagnetized, which termi- .nates at the lower end in an interior bevelgear rim, 4, is axially apertured to pass onto the reduced uppergportion of the post.

l and rabbetecl atv both ends et 5 aroundfsaid 5 axial aperture, 6., to afford angular ball seats for the anti-friction balls, D', at the Specication of Letters Patent.

Applicationled Norember 16, 1908. Serial No. 462,755.

' Patented Apr.V 26, 1910.

upper and lower ends. A take-up cone, 7, is screwed onto the upper end of the post to retain the balls in place, and the entire magnet element. on the post. This central HU member, E1, is secured by drive tit in an axial apertura? in a second member, E", of non-magnetic material, as brass, copper or aluminum, and to this second member there are secured the horse shoe magnets, E3, any convenient number of such magnets being provided, four being employed in the structure shown. The non-magnetic member, Ei is recessed to form seats for receiving the magnets E3, which fit tight in their seats, being, however, additionally secured by bolts, 9, for whose Vheads the bolt; holes through themagnet arecylindrically countei-sunk at 10, so that there shall be no pzotrusion beyond the surface of the magnet blocks. These bolts take into the member, E2." The magnets, E, are all disposed with their poles at the upper end alternating 1n circumferential order about the axis of the magnet element, so that they constitute a multipolar magnet.

The post., 2, is axially bored at 1l from its upper end, and receives at the bottom of said bore. a step bearing, 12, for the spindle, 13, of a disk, F, of material having low magnet-ic -resistance, as aluminum', which is positioned so as to be spaced a very short, distance from the upper poles of the magnet. The case, ,is interiorly rabbetcd to form a shoulder, 15, for an armature disk, G, which also serves to complete the inclosure of the .hamber in which the magnet and the disk, are located. The spindle, 13, of the disk, beside its step bearinn at 12 may be provided with a second steadying bearing at 16. at the center of the disk, G, which is penetrated by the spindle, and carries atits upper end an index finger, H. A little above. the armature disk, G, there is located a helical spring, J, connected at itsinnerendwithl the spindle and at its outer end lwith a stud," 17, mounted in the armature disk, G. The bottom, 1, of theease has an obliquely projection' hollow boss, 1S, into which' is screwed t. e journal bearing, 19, 01",.2, shaft, 105' K, having ball-bearings. at 2G; `2(l;,-'in said e journahbearing element. This. shaft, K, at

its inner-endwithin the case terminates in l' bevel pinion,` 22, which meshes with the internal bmi' geant, for rotating the magnet 110 f element. The shift, K, is designed to be' connected in any convenient manner with l connection. A

squared and vapertured at the end, 21', to indicate the intention and adaptation for such mounted/on Athe under side oi the armature disk,`G; and the collar, 26, on the spindle,

13, which constitutes the means of securing the inner end of the helical spring, J, to the spindle, is adjusted about the spindle to cause the said helical spring to hold the pin, 23, against said spring stop, 211, with slight, pressure,-that is, so that it may be Withdrawn therefrom by slight magnetic drag upon the disk F `when the magnet is rotated in thedireetion for ceiling the helical spring. The index finger, H, is secured on the spindle to register 1.rith the zero point of the dial, B, when the pin, 23, is against the spring stop, 24.

The `method and principle of operation i of this instrument will be obvious to those familiarwith magnetic tachoineter devices in common usc. llhen the shaft, K. is rotated and rotates the magnet element, the lines of 'force from (he magnetic poles to' the armature., being cut by the disk, I", produce a drag upon the disk tending to Y rotate. it in the saine direction as the magnet,

and such tendency being resisted by the spring, J, results in a partial rotation of the disk, l", causing a deiiection of the index linger around the dial proportionate to the speed of rotation of the magnet, the. tension of the spring being adjusted so that a predetermined inaxin'nnn,speed of rolation of the magnet will producitlic maxiin, 23, projects from the mum delict-.tion for which the dial is giadni ated. The amount of force involved in the drag' upon the disk, F, which produces the great, and the instrument. is sensitive to an)` extraneous disturbance. )my considerable which the disk, li. is contained, or here ble to disturb the accuracy of the indication. f which anl set through the lower side of the non-magnetic element. l'1= .impinging against is rotated is constructed. as `shown. with the Fi r this re:

'on the magnetic element which A bearing, 12, deeply thereinl there is obtained wide s read of the bearings of the spindle, 13, w ich contributes materially to the steadiness of the act-ion of the disk, F, and certainty of the speed indication which it Y gives; indeed, the construction shown in this respect very nearly dispenses with the necessity fortiie bearing, 1G, and reduces to n n almost. negligible amount the service of this bearing, for the long stemmed oscillating element Vstel-,pcd so far below the level of the oscillating disk tends to balance on that step bearing after the ymanner of a spinning top,and lateral ircssure occurs at the bearing, 16, only so ar as the enti-re instrument may be subject to jars or disturbance of position.

Preferably the step bearing. l2, for the spindle, 13,being a jewel is embedded iii the upper end of a threaded post or stein, 25, which is screwed dou-'n through the iixed post, 2, that post being-for that purpose axially bored through its entire length, and threaded for a. suitable distance to engage the threaded post, a jam-nut, Q6. being.r provided on the lower end of the threaded stem or post., :25, to secure the latter against accidental rotation. This construction provides means for vertically adjusting the step hearing, 12, to adjust the distance of the osi-illating low-resistance element, 1f', from the,

magnet oles for any purpose for which such adiustinent may at any time be desirable. Y

be adjusted axially, being moved toward oscillation and speed indication is not very tho. armature. (i, for increasing the action linger, and being moved away from the armaagnation of the air within the chamber in ture 'for diminishing such action and indiration. Such adjustment of the magnets is such agitation might atleet the. disk, is liarii'ected by means of adjusting screws. QT,

be reached for slightly slacking them it'l necessari when the magnet is to ,be thus adjusted. VThe entire case, A, is preti-:ably inclosed in a removable brass or other -ihin i'inished metal sheath, which closes the; hotes,

iis"

2S and :29, when they are provided foftba purpose stated.

I claim 1. In a magnetic tacliomefrr. ri er tion with a caseyan armature disk mounted p on the casel wall and inelosing a chamber within the case, a post within the caso coaxial with said chamber, a magnet carrier mounted-:for rotation on the. post, a vearrieractuating shaft, journaled inthe case wall and projecting into the chamber, for rotating the carrier; a low resistance disk positioned between the armature disk and one end of the carrier and mounted for osciliation about the axis of rotation of the carrier,

such carrier being provided with a plurality of peripheral recesses, and horse shoe magnets mounted in such 'recesses having all their poles toward the disks.

2. 1n a magnetic tachometer in combination with a case, a post within the ease. a permanent magnet element and au armature, one mounted for rotation on the post and the other supported fxedly on the case, and a low resistance disk positioned between the magnet and the armature. mounted for oscil lation about the axis of the rotating element; `the magnet elementy eomprlsmg a magneti rarrierof non-magnetic material,

and a -plnrality of horse shoe magnets .se-

Vcured on such earrier arranged in a circle about said axis of rotation, the carrier beincg peripherally recessed to reeelve the magnets, the latter havlng their outer surfaces substantialiy ilushwith the outer surface of the carrier. Y

- 3. In a magnetic tachometer in combination witha ease. an armature disk mounted on thedisk wall and inclosing a chamber within the caf-ze, a post within the case coaxial with .sa-id chamber, a magnet carrier mounted for rotationl on the post, a earrieraetuatiupr shaft journaled in the case wall and projectingintolhe chamber, for rotat ing the carrier; a low resistance disk positioned between the armature disk `and one f end of the carrier and mounted for oscillation about the axis of rotation ot the carrier, said magnet, carrier comprising, a central member by which it is mounted on the post; a non-magnetic member mounted on andencompassing said central member and having a :plurality of peripheral recesses and horse shoe magnets secured fixedly in such recesses Y with their poles faeingjoward said' disks.

4. In a magnetic taehonieter, in combination with a case, a rigid post. withinthe case; a permanent magnctelement and an amature, one mounted for rotation on the post and the other supported tixedly on the i case; a low-resistance disk positioned between the magnet and the armature having' a spindle provided with a step 4l aringgj within the post and extending through the fixed element; a spring which operates to hold the disk i-'ieldinglyV against. rotation from a predetermined position; anindieaior earried b v thespindle. and means for adjusting the magnet axialiv with respect to the distance of its poles from the armature.

In a magnet-ic taehometer. in combination with a ease, a rigid post within the case; a permanent, magnet element and :xa armature, one ymounted for rotation on the post and the other supported fixedly on the case; a .low-resistance disk positioned be.- tween the magnet and the armature having a spindle provided with a step bearing with in Vthe post and extending through the fixed element; a spring which operates to hold the disk yieldingly against rotation from a predetermined position; an indicator carried bv the spindle, the magnet. element comprisini; a. plurality of horseshoe magnets and a' carrier on which they are rigidly mounted, and

means for adjusting the magnets longitudi- 3 -nally on the carrier to varyy the distance from their poles to the armature.

6. In a maf'netic taehometer, in combination with a, case, a rigid post within the case; a permanent magnet element and an armature, one mounted for rotation on the postand the other supported ixedly on the case; a low-resistance disk positioned be tween the magnet. and the armature having; a spindle provided with a .step bearing with in the post and extending through the fixed element; a spring which operates to hold the disk yieldingly against. rotation from a redetermined position; an indicator carrie by the spindle; the magnet comprising a plurality of horseshoe magnets; a non-magnetic i carrier having seats for the horseshoe magnets; .screws set. through said'carrier iu.- pinging` againstthe neck or bow of the horseshoe magnets respectively, the ease'having an aperture through which such screws are accessible. r e

In testimony whereof, I have hereunto set my hand, in the presence of two witnesses, at Chicago, Iliinois,'this 12th day of November, 1905.

JOHN K. STEiVART. In the presence of- J Um S. Aorr, M. Garraum: ADY.

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