US2291639A - Centrifugal switch - Google Patents

Description

Allg. 4, R LEE CENTRIFUGAL SWITCH l/NVENTQR ROYAL. LEE

BY 4 Al l/VSULAT/ `Filed May 16, 1940- 26 J4 47 .31 .55 FIG Patented Aug. 4, 1942 2,291,639 caN'rmr'UGAL swrrcn Royal Lee, Milwaukee, Wis., assignor to il.

Engineering Research Corporation, Milwaukee,

of Wisconsin Wis., a corporation Application May 16, 1940, .Serial No. 335,461

(Cl. 20o-80) 8 Claims..

The present invention relates to speed-respon= sive devices andmore particularly to centrifugal switches.

It is an object of the invention to provide an improved centrifugal switch which will operate smoothly -and accurately throughout a wide range of speed-settings.

A`Another object is to provide a centrifugal switch which can be economically manufactured' and which has an adequate currentwarrying capacity.

The invention further consists in the several features hereinafter described and claimed. In the accompanying drawing, illustrating cer- ."/tain embodiments of the invention,

Fig. 1 is a sectional elevation showing one form of centrifugal switch constructed in accordance with the invention, the switch being mounted on an electric motor and being adjusted for operation at high speed;

y Fig. 2 is a front elevation ci the switch;

Fig. 3 is a top view;

Fig. 4 is a bottom view;

Fig. 5 is a sectional elevation taken generally Fig. 6 is a side elevation of the switch, parts being broken away and parts being shown in section, and the switch being adjusted for operation at low speed;

Fig. 'l is a side View, partly in section, oi a modied form of centrifugal switch, the switch being adjusted for operation at high speed;

Fig. 8 is a front elevation of the switch ci Fig. "i, and

Fig. 9 is a top view, similar to Fig. 3, showing another form of centrifugal switch in which the contacts are adapted to engage upon increase of lmounted on the rotatable member il and are preferably in the form of flat concentric collector rings or disks mounted on one side ci the insulating disk i9. As seen in Fig. l, brushes 2.5i and 24 bear on the respective collector rings il and 22 and are here shown to be carried by the motor frame.

Rigidly secured to 'the insulating disk lil, by a plurality of rivet-forming studs or posts le and cooperating screws is a generally circular, ill-shaped frame or plate 2l which is formed oi a suitable metal such as duralumin. The studs or pests 2li also serve to secure the outer collector ring, 2l, to the insulating disls and to electrically connect the metal frame 2l to this collector ring. The t3-shaped frame 2l extends at right-angles to the disk anis and in spaced relation to the disls, and has a gap between its ends. A plurality of contacts @il are detachably secured to the spaced end portions oi the plate El in on center relation to the dist. axis and have their contact faces lying in a plane normal to the disk axis. The Contact heads are preferably formed of. tungsten or other resistant metal. ln the present instance, each end portion o the plate is shown to carry two contacts. A balancing segnient Sii is secured to the plate 2T! at the peripheral region thereof dlametrically opposite the contacts 2Q.

lDisposed. between the insulating disk i9 and metal frame ill is a iorlsed, plate-like, oscillatory lever which is hingedly supported on the insu-s lating disk by a pau of rivet-fore posts or studs 32 and cooperating screws engaging the ends of a irl-shaped hinge-orming leaf spring to, the latter being riveted or otherwise secured to side extensions oi the lever. The :trame 2l is provided with openings 35 for access to the screws 33. The plane oi the lever 3i is approximately at right angles to the anis of the disk, and the longitudinal center line oi the lever eX- tends diametrically with respect to the disls axis. The posts or studs 32 also serve to secure the inner collector ring, 222, to the insulating disk and to electricalliT connect the lever to this collector ring. The inner collector ring is further secured to the disl:` by rivets 36. The lever 3i is formed of a suitable light-weight metal such as duralumin. A plurality oi contacts el are detachably secured to the free ends of forli arms of the lever 3l and cooperate with the contacts 29 on the metal frame 2l, the lever contacts being normally urged or biased against the frame contacts by the hinge spring tl. The eiective' hinge axis of the lever extends in a transverse direction with respect to the disl; axis and at one side of the disk axis, while the contacts 3l are arranged at the opposite side of the disk axis. The lever contacts are movable in a direction approximately parallel to the disk axis.

The oscillatory lever ll carries thereon a weighted centrifugally actuated member 98 which is shiftable with respect to the lever to inoscillatory lever Il. as by means of a cross shaft 39 extending parallel to the hinging axis of the oscillatory lever and having reduced ends jour-v nailed in bearing members 40 secured to the fork arms of the oscillatory lever. The auxiliary lever 39 extends radially of the disk axis and is movable in the space between the 'fork arms of the lever 9| and in the gap 29 between the ends of the c-shaped frame 21. 'I'he axis of the cross shaft 39 extends in the region between the disk axis and the contacts. The outer end of the auxiliary lever 98 carries an off-center weight member 4| which extends angularly in a direction away from the insulatingv disk and which is secured to the lever by rivets 42, one of these rivets also serving to lock the cross shaft 99 to the weight member. The inner end of the auxiliary lever 3l is disposed at the axis of the disk and carries a rounded metal button 43 against which is adapted to bear the rounded insulating tip 44 of an adjusting screw 45, the latter extending axially of the disk and movable in the central open space of the c-shaped frame 21. In order to permit adjustment of the screw while the switch is operating, the screw is carried in a stationary uscrew-threaded support 46. Inward movement of the inner end of the auxiliary lever Il is yieldingly resisted by a leaf spring 41 which extends in a radial direction and. has its outer end riveted or otherwise secured to the hinged end portion of the oscillatory lever Il, the inner end of the spring 41 having an embossed rounded end which bears on the inner side of the button 4I. The spring 41 holds the button 43 against the tip 44of the adjusting screw 4l, and the inward displacement of the spring by the screw serves to counteract the biasing force of the hinge spring I4.

'Ihe centrifugal switch may be used in any suitable circuit and by way of example it is here shown to be included in series with motor windings comprising a pair of series field windings 4l and an interposed amature 49, the field windings being connected to line conductors Il. 'I'he brush 23 is connected by a conductor Il to one of the motor brushes and the brush 24 is connected by a conductor I2 to one end of one of the field windings 4I. thus placing the centrifugal switch in series with the motor windings. In some instances the switch is shunted by a resistor Il and by a protective device such as a condenser I4. By placing the switch in circuit between the field windings, the latter will form choke coils or reactors in both line conductors to prevent or mlnimize the tron to these conductors of electrical disturbances that may be caused by the operation of the switch. The motor windings may be those of the motor Il or of a separate motor.

\ When the centrifugal switch of Figs. 1 to 8 is at rest the contacts l1 are urged by their springmounted supporting lever 3l into engagement with the contacts 29 carried on the frame 21. The contact engagement will be maintained throughout the normal range of adjustment of the speed-setting screw 49. For adjusting the switch to open at a high speed the screw is turned outwardly to the position shown in Fig. 1, thus causing the weighted lever 39 to turn counterclockwise (as viewed in Fig. 1) under urge of the spring 41 and reducing the eii'ective force arm of the weight 4I with respect to the cross shaft 99. Upon setting the motor shaft Il in rotation the centrifugal force on the weight 4| will tend resilience of the hinge to turn the auxiliary lever I8 counter-clockwise (as viewed in Fig. l) about the cross-shaft Il. and since the lower end of the lever 3l bears 0n the adjusting screw 45 there will be an inward pressure on the contact-carrying lever 9i, opposing the pressure of the hinge spring I4 and tending to separate the lever contacts 31 from the frame contacts 29. Upon the attainment of a certain critical shaft speed, determined by the spring 94 and force arm of the weight 4I, the centrifugal turning moment produced by the weight 4I will become sumcient to move the lever 3| inwardly and cause the lever contacts I1 to move out of engagement with the frame contacts 29. As a result, the electric circuit through the brushes 2l and 24 will be interrupted by the separation of these contacts. If it is desired to have the centrifugal switch operate at a lower speed-setting. the screw 4I is turned inwardly, as to the position seen in Fig. 6, causing the weighted lever to swing clockwise (as viewed in Fig. 6) and inwardly flexing the spring ,41. 'I'he contacts will then separate at a somewhat lower critical speed determined by the reduced effective force of the hinge spring I4 and the increased force arm of the weighted lever 99. By turning the screw 44 inwardly from the position of Fig. 1 to the position of Fig. 6. the speedsetting of the switch will be progressively reduced through a wide range. If the screw is moved inwardly a sumcient distance, the lever contacts 3| will remain separated from the contacts 29, even when the switch is at rest, and if Athe screw is moved outwardly a sumcient distance, the contacts will remain in engagement regardless of the speed of the shaft. In the latter case the force arm of the weight member 4I will be zero or very small.

In the arrangement shown in Fig. l, the centrifugal switch is employed to control the seriestype electric motor Il by which it is driven. As soon as the motor` accelerates to the critical speed, the contacts 2l and I1 separate, thereby introducing the resistor I3 in series with the motor windings. The motor speed then drops slightly below the critical speed. whereupon the contacts29andl1againengagetocaiuethe motor speed to increase. In practice. the oscillatory contact-carrying lever 3| of the switch vibrates at a relatively high frequency. and al a result the adjusted motor speed remains substantially constant.

It will be noted that the speed-setting of the lcentrifugal switch is aifected by two factors, one

the variation of the effective spring action on the oscillatory contact-carrying lever 3l and the other the variation of the effective force arm of the centrlfugalLv 'actuated weighted lever 8l. As a result of these two factors. and especially the latter. the switch will operate in a satisfactory manner over a wide range of speed adjustments. At high speeds tion is relatively strong and the eective force arm of the weighted lever Il is relatively short, thus avoiding excessive centrifugal action. At low speeds the effective spring action is relatively weak and the eiiective force arm of the weighted lever Il is relatively long. thus obtaining the eifective spring ac- A sive windage losses.

replaced if shown in Figs. 7 and 8, the pivot a favorable centrifugal action on the weighted lever.

The plate-like contact-carrying members of the switch extend in planes approximately normal to the shaft axis, thus providing for eiiicient cooling of the off-center contacts without exces- The construction of the switch readily permits the use of a plurality of contact pairs so as to provide adequate currentcarrying capacity, and the contacts can be easily necessary. The switch is of such construction that it can be economically manufactured, the parts thereof being capable of inexpensive fabrication and easy assembly.

In the modified form of centrifugal switch `shaft 39 and spring 41 of Fig. 2 are omitted, and the weighted lever |38 (corresponding to the lever 38) is hingedly carried on the forked oscillatory lever 3l by springs 39. The springs are here shown to be leaf springs of E-shaped configuration, the free ends of the outer arms of the springs being secured by short riveted posts or studs it@ to the oscillatory lever, and the 'free ends of the intermediate arms of the springs being secured to. side extensions it of the weighted lever. The connecting bars of the E-shaped springs are in alignment and extend transversely of the oscillatory lever. The angular displacement of the weighted lever |38 by the adjusting screw 45 is yieldingly resisted by the hinge springs i3d. The construction and operation of the switch of Figs. '7 and 8 are otherwise the same as that of Figs. l to 6.

The modified form of centrifugal switch shown in Fig., 9 is generally similar to that of Figs. l to 6 except that the contacts have been reversed so as to be normally open, thus adapting the switch to be used in various circuits requiring this contact relation. For lthis purpose the contacts 29 are reversed on the spring-mounted oscillatory lever 3l to face the insulating disk i9 and to engage cooperating contacts itl detachably mounted on a at annular supporting frame itl secured to the disk i9 and outer collector ring 2| by spacing studs or posts V25 and associated screws E26. The studs B25 correspond to the studs 25 ci Fig. 3, and the frame lil corresponds to the plate 21 of Fig. 3. The contacts 29 and H31 of the switch of Fig. 9 are normallyopen,

vand upon attainment of a critical shaft speed,

the centrifugally actuated weighted lever te causes the contacts to engage. The construction and operation are otherwise the same as that of the switch of Figs. 1 to 6. The modification shown in Fig. 9 may also be'applied to the switch of Figs. '7 and 8.

Certain embodiments of the invention have been shown and described, but it will be obvious to those skilled in the art that modifications may be made without departing from the spirit and scope of the invention. f

What I claim as new and Letters Patent is:

l. In a centrifugal switch, the combination of a rotatable member, a contact carried by said member, a lever swingably mounted on said member vand movable in a generally axial direction with respect to said member, said lever being spring-urged in one direction, a contact carried by said lever and cooperating with said firstnamed contact, a weight member having a pivdesire to secure by d otal mounting on said contact-carrying lever to swing about an axis transverse to the axisof said rotatable member and centrifugally actuated to urge said contact-carrying lever in a direction opposite to its spring-urged direction, means for angularly displacing said weight meter with respect to said contact-carrying lever to adjust the effective arm of force of said weight member with respect to said lever,'and resilient means normally urging said weight member in a direction reducing said arm oi force.

2. In a centrifugal switch, the combination of a, rotatable member, a co'ntact carried by said member, a lever swingably mounted on said member and movable in a generally axial direction with respect to said member, said lever being spring-urged in one direction, a contact carried by said lever and cooperating with said rstnamed contact, a weight member having a pivotal mounting on said contact-carrying lever to swing about an axis transverse to the axis of said rotatable member and centrifugally actuated to urge said contact-carrying lever in a direction opposite to its spring-urgeddirection, angularly displacing said weight member with respect to said contact-carrying lever to adjust the eiective arm of force of said weight member with respect to said lever, and resilient means normally urging said weight member in a direction reducing said arm of force, said resilient means being carried on said lever to reduce the biasing force on said lever when the arm of force of said weight member is increased.

3. lin a centrifugal switch, the combination of a rotatable member, a contact carriedtby said member, a lever swingably mounted on said member and movable in a generally axial direction with respect to said member, said lever being spring-urged in one direction,- a contact carried by said lever and cooperating with said first-named contact, a weight member having a spring hinge connection with said lever to swing vabout an axis transverse to the axis of said rotatable member and centrifugally actuated to urge said lever in a direction opposite to its spring-urged direction, and means for angularly displacing said weight member with'respect to said lever to adjust its effective arm of force with respect to said lever, said spring hinge connection normally urging said weight member in a direction reducing said arm oi force.

d. In a-centrifugal switch, the combination of a rotatable member, a contact carried by said member, a lever swingably mounted on said member to move in a generally axial direction with respect to said member, said lever being spring-urged in one direction, a contact carried by said lever and cooperating with said firstnamed contact, a centrifugally actuated weight member pivotally carried by said lever for urging said lever in a direction opposite to its springurged direction, the pivotal axes of said weight member and lever being generally parallel and extending transversely of the axis of rotation of said rotatable member, and means for angularly member to move in a generally axial direction with respect to said member, said lever being spring-urged in one direction and having forked free end portions forming an opening between them, contacts carried by the forked portions of means forthe lever and cooperating with said rst-named contacts. a centriiugally actuated weight member pivotally carried by the forked portions o! the lever and movable in said opening, and means iorangularly shifting said weight member with respectto said lever to adjust the arm ot i'orce oi' said weight member and to thereby adjust the speed setting o! the switch.

6. In a centrifugal switch, the combination of a rotatable member, a frame mounted on said member and having an opening. contacts carried by said frameon opposite sides of said opening, a lever swingably mounted on said member to movein a generally axial direction with respect to said member, said lever being spring-urged in one direction, contacts carried by said lever and cooperating with said mst-named contacts. and a centritugally actuated weight member mounted on said lever for urging said lever in a direction opposite to its spring-urged direction, said weight member being movable in the opening oi' said frame.

7. In a centrifugal switch, the combination of a rotatable member, a contact carried by said member, `a lever swingably mounted on said member to move in a generally axial direction with respect to said member, a contact carried by said lever and cooperating with said ilrst-named contact, said lever being spring-urged in a direction to eilect disengagement of said contacts, a centriiugally actuated weight member shiitably carried on said lever i'or urging said lever in contact-closing direction, and means ior shifting said weight member with respect to said lever to adjust the arm ot torce of said weight member and to thereby adjust the speed setting oi' the switch.

8. In a centrifugal switch. the combination oi' a rotatable member carrying a pair oi' contacts, resilient biasing means for one of said contacts, centriiugally actuated means carried by said member for relatively displacing said contacts and including a shiftably mounted weight member having a variable arm oi' force. resilienty means normally urging said weight member in a direction reducing said arm oi' force, and means to adjust said arm of force to thereby vary the speed setting of the switch.

, ROYAL LEE.

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