US2977931A

US2977931A - Overspeed safety devices

Info

Publication number: US2977931A
Application number: US50341A
Authority: US
Inventors: Donald E Schott
Original assignee: Thomas C Wilson Inc
Current assignee: Thomas C Wilson Inc
Priority date: 1960-08-18
Filing date: 1960-08-18
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04

Description

April 4, 1961 D. E. scHoTT 2,977,931

ovERsPEED SAFETY DEVICES Filed Aug. 18, 1960 l l FE 1N ENToR.

` 'wit lexcessive speeds. The newl device is` simple andiineiipen-y United States Patent C y Y 25971931 y l l e pg ovERsPEED-'SAFETY-DEVICES1 Donald'E. Schott,.Emersony*.NQ., assignor Vto Thonias C. Wilson', Inc.) Long Island City, N.Y., corporation of the compressed? air APatented Apr. 4, 196i Figi'.` 1V is: a fview' of' the'fl'ongitudinalcross-sectional, view through aivportion'lof atzpneumatic grinder provided with asgovernor andthe safety device of the invention;l

fFig., 2li`si akview ins end elevation of the shut-01T jaw ofttherdevice;

Fig-3 isafviewin. side elevation showing the jaw f mounted on: the1body of: the governor;

ay beleniployed"Withpneumaticmotors forvariz- 'pnrpo alllit's advantages arerealizedIin'itsuse p'eurritle'ally? driven` hand-held 'i grinders and anrernp tovaiV partlof thezliandlelt):Whichdetines. an opening Zlaf vgood operating condition; 'servetlieir irre,

,emor-is likelyto result in the development of excessive f. oversp"`e`ed-safetydeviceV off'fthe: invention fnctions` which air passes to the motor. As long Jas-tletmotoif does he governor tis inettectiv'e The for? a-fplnra'lity 'ofsballsi-an'd Y Fig. 4 is an exploded'longitudinal sectional view of the safety device and governor;

FirgtSfisLa: view lin'l perspective showing the pivoted WeightslofT the governor; `and` Fig. 'is-anend view ofth'eiretainer.

'I'he'pneumatic `hand-'heldV grinder, of which part is illustratedi-in`Fig5. l; comprises'ahandle 10'secured by bolts 'to' taacasingilI- enclosing Vthe pneumatic motor,u which hasA aiishaftalzmount'edfori rotation in a ballV bearing Y indicated diagrammatically at.13; The shaft has an end seetionf212al oflreduc'edzdiaineter' and the hub 14a of the body 14 of-a governoristhreadedi on thesection. The 'bodyl'hasa diarnetrieal ,ange 15 at the end of the hub lreinoteifr'omfthefmotorshaft' and a, pair of wings 16 project.:'front'therilangeorr'oppositesides of and parallelY to"theaxis: of'fltheiinotor shaft.- Apair of weights 17 are pivotallynfountedfonrespective pins 18 having their mends:` in kopenings'in the wings and each weight has an- -earl" 1.711y extending.; radiallyandlying adjacent to the ilange 15. ,y o fr AlheLhandle Ill containsanxinternal partition' 19 formlingraffclrambenfserving;*aszalrousingffor the. governor and a; 'bushingrzll fis threadedin an opening in'the housing'wall cocentriclwitlzthe imotor shaft and is formed with an inner surfa'ceof thehousing defined by the partition 19.

Theisleeve]hasiafpor't` 28a throughits cylindrical wall and,

.fvvheril the'sleeve is Tin proper angularrpositiom'the port registers rwithatpassage 29"v leading through the wall: of thesfhonsingit therfinterior of the ymotor casing 1.1*V The sleeve islalso provided` with a" pair of diametrically dis'- poseduinternaltlngs' 2811:'

but, if excessive motor. speed develops, the balls arey 1y- .e1-length@ 'guiaewyfst by centrifugalY ply`s`top'sthemotor `and it cannot be started again until `the balls jhavek been restored toj their seats andvthejaw and the s'leevelhave been returned to their initial posif tions with the port in the sleveregistering with the port inthe housing wall.

l 2 Forafbetterunderstanding the inventionrreference t xinay-.be-made tothe accompanyingjdrawing, in which The" `ovv fof-fairrfrorntheichamber 122 'through the bush- Y 120; "the-sleeve 28;.an'd thepassage 29 is controlled Y 4bythexa'otionfof tlteigovernor. Por this purpose, the

` 'gdvein'orrse-providedfwith"afcylindrical valve member 30 sleeve IAstier@result-i` the.sleeveisidausdto rtteivv'ith the jaw and the rotation ofthe.: sleeve cuts oit the air t supply tothe rnotor `except during the ,shortperiods t when` the port in :the sleeve is passing across theopen ing in the housinghwall.' Thecutting -oi of the air sup-` havingjlelosed end` with'ra 'centralfopening through which agbolt 3,1 loosely extends. The bolt is threaded into" the ihodyrfllt'fofithe governor andrtintothezend of the'motor shaft-andi its"A head-f3 las is ofifa'diameter.: slightly l'less than the internally diameter of the'valve-member Sil. A spring 32 encircling the bolt bearseat one end against the under' side of the head and, at therother, against theend of. the valvemember 30.

In the operation of the devi-ce, *thev governor body rotateswith the motor `shaft and,'as the motor-jA speed lincreases,vthe weights 17 are swung byucentrifugal. force;

so that their'ears 17a engagethe end of the 'valve mem-Y ber `30'and move the member toward the seat 20a e131-, Vcirclingthe opening throughb'ushing 20.` l As the valve l member approaches the seat, the. cross-sectional areaof l -on the shut-off sleeve.

3 the passage for air through the bushing is reduced and the motor speed is correspondingly reduced.

The overspeed device of the invention includes the shut-oif sleeve 28, a retainer 33, and a shut-off jaw'34. The retainer includes a'sleeve 33a 'threaded on the hub 14a of the body of the governor and lying at the side of the flange 15 facing the end of the motor shaft. The

retainer also includes a radial ange 33b at its innerA end and a plurality of seats for balls are provided by. openings 33c partly in the sleeve 33a and partly in the flange 33b. A radial guideway 33d extends outwardly `from each seat. i

The cut-off jaw 34 includes a ring 34a which encloses and is slidable on the sleeve 33a of the retainer, and a pair of arcuate extensions 34b'from one end of the ring, which are spaced lsufciently to receive the ange 15 of the governor body between them. Atits opposite end, the ring is formed with ange 34e, the outer face of which is formed with an annular radial seat 34d connected by a conical surface 34e to an annular radial surface 34f. A pair of lugs 35 are formed on the ange and extend parallel to the axis of the ring 34a.

A spring 36 encircles the ring 34a of the shut-0E jaw and bears at one end against the ange 34e and, at the other, against the flange 15 on the governor body. The spring urges the shut-off jaw toward the ange 33b of the retainer so that balls 37 lying in the seats 33e of the

radial surfaces

33b and 34e on the retainer and shut-olf jaw, respectively, and there is no force tending to move them inwardly toward their seats. The resetting of the device, accordingly, requires that the balls be returned to their seats and that the shut-oif sleeve be adjusted to place its port in registry with the air passage 29. In order to reset the device, the handle 10 of the grinder is detached fromthe motor housing and, as the handle is removed, it takes the shut-off sleeve with it. The governor is then exposed, so that it can be restored to proper operating condition, and the balls of the safetyr device can also be reseated. Finally, the shut-off sleeve is adjusted angularly to proper position and, when the handle 10 is again attached to the motor housing 11, the grinder is ready for further operation.

I claim:

1. An overspeed safety device for use with an air m0- tor having Aa housing with openings for inlet and outlet of air, a valve member within the housing for controlling the ow of air through the housing, a motor shaft entering the housing, and a governor driven by the shaft and operating the valve member, the governor having a body with a hub encircling and fast on the shaft, which comretainer are held in their seats by contact with the an- I nular seat 34d and the conical surface 34e on the shutoff jaw.

'The housing 38 in the motor casing for the ball bearing 13 has an end section overlying the adjacent end of the shut-off sleeve 28 and the end section is formed with an internal annular channel 38a. A rubber O-ring 39 is mounted in the channel to bear against the surface of the sleeve 28 and normally holds the sleeve against rotation.

During normal operation of the grinder equipped with the safety device, the balls 37 of the device lie in their seats 33C in the retainer 33 and the annular seat 34d and the conical surface 34e on the shut-o jaw 34 are held in contact with the balls by the spring 36. The shut-olf sleeve 28 is initially adjusted with its port 28a in register with the air passage 29 and the sleeve is held inthis position by the 0ring. When the motor is operating, the retainer rotates with the governor body and, although the shut-oft` jaw is mounted loosely on the retainer sleeve, the jaw also rotates with the governorbody because its extensions 34b lie on opposite sides of the ange 15 on the governor body. The shut-off sleeve is at rest. If the rated motor speed is exceeded, centrifugal force moves the balls out of their seats and they roll outwardly in their guideways and on the radial surface 34j on the shutoff sleeve. In such outward movement, the balls cause ythe jaw to move along the sleeve section 33a of the retainer until the lugs 35 on the jaw engage the lugs 28b The sleeve then rotates with the jaw and, in such rotation, the port 28a on the sleeve registers with the air passage 29 only for a brief, period during each rotation of the sleeve with the Yresult thatl the air supplied to the motor is so greatly reduced that Y the motor stops.

env

prises a retainer mounted to rotate with the shaft and having circumferentially spaced ball seats and guideways with radial surfaces leading from the seats, balls in respective seats, a shut-olf jaw mounted for rotation with and movement axially relative to the shaft and having an annular seat opposed to the retainer seats and a radial surface opposed to the guideways, means urging the jaw toward the radial surfaces of the guidewaysv and against the balls, means operable on rotation to reduce the flow of `air through the housing, and co-operating parts on the jaw and reducing means for connecting them for rotation in unison upon movement of the jaw axially of the shaft `away from the radial surfaces of the guideways.

2. The device of claim 1, in which the reducing means is a sleeve mounted in the housing against the inner surface thereof for rotation about the axis of the shaft and `having a port registering with one of the housing openings in one angular position of the sleeve. 0

3. The device of claim 1, in which the retalner is mounted to encircle the governor body hub and is fast thereon.

4. The device of claim 3, in which the shut-off jaw is mounted to encircle the governor body hub and is movable endwise thereon and connected to the governor body for rotation therewith.

5. The device of claim 4, in which the reducing means is a sleeve mounted in the housing against the inner surface thereof for rotation about the axis of the shaft and having a port registering with one of the housing openings in one angular position of the sleeve, the sleeve at leastpartially enclosing the jaw.

6.4 The device of claim 5, in which the sleeve has internal lugs and the jaw has lugs engageable with the sleeve lugs for connecting the sleeve and jaw for rotation in unison. y

References Cited in the tile of this patent UNITED STATES PATENTS