US2256781A - Overload release mechanism - Google Patents

Description

Sept. 23, 1941. F. R. NELSON OVERLOAD RELEASE MECHANISM 2 Sheets- Sheet 1 Filed Sept. 6, 1940 Sept. 23, 1941.

F. R. NELSON OVERLOAD RELEASE MECHANISM Filed Sept. 6, ,1940 2 Sheets-Sheet 2 Patented Sept. 23, 1941 OVERLOAD RELEASEMECHANISM Floyd R. Nelson, Rockford, 111., assignor to Gotta Transmission Corporation, Rockford, 111., a corporation of Illinois Application September 6, 1940. Serial No. 355,701

This invention relates to a new and improved 20 Claims.

overload'release mechanism for electric motordriven devices, as, for example, motor-driven domestic stokers. I i

In the past, stokers have ordinarily been equipped with shear pin type release mechanisms, but these have been objectionable because of theadded work connected with replacing the shear pin when the stoker has been automatically shut off by reason of jamming of the feed screw. It is therefore the principal object of my invention to provide a release mechanism of a simpler and more economical construction wherein the drive is disconnected in the event of excessive resistance to turning of the driven shaft of the feed screw driving transmission and the motor circuit is also automatically broken to stop the motor, the mechanism being devoid of any shear pin but having instead a kick-out member which requires only resetting after it is kicked out due to the overload, the resetting being as simple as pressing a button.

Another important object of v the invention consists in incorporating the kick-out member in' the belt driven pulley where the manually operable resetting pin or knob thereon is easily accessible.

,Still another object consists in providing the motor switch j in a housing arranged to be mounted in proximity to the pulley where a rotary pendant switch-operating member carried by thehousing is arranged to be struck by the reset pin only when the kick-out member has been kicked out, whereby to open the switch.

The pendant member when swung upwardly is i arranged to be locked releasably in the open circuit position by a latchmember one side of whichbears against the spring-pressed plunger of the switch and the other side of which has a detent notch therein to accommodate the pendant member in the raisedopen circuit posi- Fig. 2 is a section similar to a portion of Fig.1; showing the motor switch-operating mechanism in Vertical section in the plane of the line 22 ofFig.6; "1

Fig. 3 is aview of the inner side ofthe pulley taken on the line '3--3 of 'Fig. 1 with a portion of the cover plate broken away for better il-'- lustration; v Fig. 4 is a similar view showing the kick-out member in the kicked out position; FigQB is a rear view of the switch housing indicating diagrammatically the radius of operation of the reset pin with relation to' the'switchoperating mechanism under normal conditions, and Fig. 6 is a similar view indicating the larger radius of operation of the reset pin after the overload has occurred, and showing the parts of the switch operating mechanismin moved posi tion.

The same reference numerals are applied to corresponding parts throughout the views.

Referring first mainly to Fig. Lthe reference numeral 1 designates the housing of a domestic stokerdrive transmission for driving the usual coal feed ,screw. 8 is the driven shaft of the transmission to which is keyed as at 9, a hub H). A drive pulley H is rotatable on the bearing portion. l2 of the hub l0 and is retained in place by a washer l3 and cotterpin I4.' The pul ley is of a stepped cone type and is adapted to receive the V.belt 15 in either one of itsthree grooves according tothe speed .at which the stoker. feed screw is to be driven. Anelectric motor, not shown, carries the companion stepped cone pulley over: which thebelt l5 passes, and

' it is' that motor which the switch 16. hereinafter tion. Thelatch member is arranged to be tripped manually to release the pendant member after the kick-out member has been reset and everything is in readiness for restarting the motor. 'The invention is illustrated in the accompanying drawings, in which I .Fig. 1 is a longitudinal vertical section through the drive pulley portion of a stoker drive transmission showingthe overload release mechanism ofmy invention, the switch-operating mechanism .beingshown in this view in vertical section on the line l-I of Fig. 5 and the pulley being in section on the broken line l-l of Fig. 3;

referred to controls. At .l'l there is indicated generally an overload release mechanism incorporated in thepulley, in accordance with my invention, providing a driving connection .between the pulley H and hub I0 so long as'there is no abnormal increase in resistance to. turning of the feed screw as reflected by a proportionate increase in resistance to turning of, the driven shaft 8. I8 is the reset pin or knob projecting from the back of the pulley and normally operating on the small radius a, as indicatedin Fig. 5, but arranged to operate on the. larger radius 12', as indicated in Fig. 6, after thbver loadhas caused the release mechanism .11 to disconnect the pulley II from driving relation to the hub It]. At I9 thereisindicated generally the switch operating mechanism arranged to be operated by the reset pin l8 after the pulley connection of the pulley- II from driving relation to the hub l0. Most stokers have an obstruction clean-out plate on the end of the coal feed conduit next to the hopper where the foreign body is usually found to lodge, and once the obstruction has been removed and the stoker is ready to resume operation it is not necessary with the present invention to replace a shear pin, as in the other stokers having other types of overload release mechanisms. It is only necessary with the present invention to resetthe overload release mechanism I! by depressing the reset pin lgpwhi ch as will soon appear, requires no 1 more efiort than pressing a push button. Then the stokeris in readiness for restarting the motor, and the switch-operating mechanism 9 includes a latch 20, which, as will soon appear, maybe tripped manually to closethe switch it and3start the motor. N f V V 7 Referring now to Figs. 1, 3 and 4, the overload 3 release mechanism I 1' comprises a kickout member 2| pivoted on the web portion 22 of the pulley I, as indicated at 23; This member is elongated and carries the reset pin or knob 3' on the free; ,endportion thereof in transverse relation thereto projecting freely through a, slot 24 1 in a :cover plate 25 fastened to the rim portion 26' of; the pulley-1| as by means of screws 21,

this plate having a central hole 28 provided therein through-which a-portion of the hub I projects, as clearly appears in Fig.1. A cam projection 29 on the kick-out member 2| intermediate the ends thereof has its inclined cam surrow-c, the hub I0 is driven with the pulleyand the-coal feed screwvof thestoker which relies Ior-its drive upon the shaft 8 will accordingly be driven= The leaf-spring 33'mounted on the inlengagement with theinner head end of an f adjustable screw 35 mounted radially'in the rim 26.61? the pulley has a bent free end portion .36 --arranged to hold the kick-out member 2| in drivinglposition against the c-amaction of the projection 29 onthe drive pin 32 tending to kick member, due to the fact that there is no shoulder on the leaf-spring obstructing the return movement and only slight deflection of the spring 33 is required, as should be clear from a study of Fig. 4. The pin or knob l8 projects sufliciently from the pulley II, as clearly appears in Fig. 1, so that it is easy to press inwardly on it in the direction of the shaft Bto reset the kickout member 2| from the position of Fig. 4 to the position of Fig. 3. By adjustment of the screw 35 inwardly toward the spring 33, the 7 force required to kick out the member 2| against 1 face or' s'houIder 30 arranged slidably to engage the cam surfaceorshoulder 3| on a drive pin 1 32 mounted in the hub, I U and projecting radially'therefrom; =So long-as the-cam projection j .29 :is disposed in engagement with the drive-pin 32, as shown imFig. 3,:whereinthe directionof j rotation ofthe pulley isindicated by the arweb 22- ofthe pulley on a stud 34and disposed out thdmember 2| toward the position shown 1 inf-Figiil wherein .the freefendportion .of the kick-outlmember -2|-.is disposed in engagement .with' the .extreme outer end portion 31. of the j leafi-fsprin'g33 in engagement with a stopBBpro- 'yidedgby the, end portion of the spring which is bent'lapproximately at right angles toward the kickeoudmember. The bent portion. 36 of the l leafrspring-33 is so inelined in relation to the iirounde'digfree, end .39 of. the kick-out, member andextends transversely. relative to the path of movement." of the end portion of the kick-out member so that "a certain predetermined force is f required. to niove the kick-out member 2| outwardly against the resistance of the sprin .33, i this tom's being, on 'theotherhand, many times greater than that required to return the kick-out janism 9.

resistance of the bent end portion 36 of the spring 33 can be greatly increased, while, on the other hand, outward adjustment of the screw away from the spring 33 will decrease the force necessary to kick out the member 2|. In that way, it is a simple matter to set the release mechanism IT to disengage the pulley II from driving relation to the hub l0 within a certain range above thenormal resistance to turning of the shaftB, so that on the one hand there will be no danger of the coal feed screw drive being disengaged due toa slight fluctuation in the amount of powerrequired to turn the feed screw, and on the other hand there will be no question in regard to the positive disconnection of the drive when a spike, rock, or other serious obstruction, causes jamming of the feed screw. The screw 35 will, of course, be properly adjusted at the stokermanufacturers plant and should not require readjustment thereafter. A lock nut 40 on the screw is arranged to be tightened against the rim 25 of the pulley to secure the screw in its adjusted position.

Referring now principally to Figs. 2, 5 and 6, attention is again called to the fact that the pin 13 under normal driving conditions moves in a circle having the small radius indicated at a in Fig. 5, whereas upon disconnection of the pulley I from driving relation to the shaft 8 by reason of the kicking out of the member 2|, due to unusually great resistance to the turning of the shaft 8, the pin l8 in the subsequent free turning of the'pulley 'moves in a circle'having the larger radius h, indicated in Fig. 6. The switch It, previously mentioned, is mounted within a housing 4| suitably secured-to the housing 1 of inFigs. 1 and 2] Electrical conductors for the motordriving the pulley l are extended through conduit entered in the hole 43 in oneside of the housing 4| in proximity with the switch 6. The switch It may, of course, be of any suitable or preferred type, but is preferably of a snap action type'to snap on and ofi having a spring p'ressed plunger 44 tending normally to move outwardly toward closed circuit position but arranged to be moved inwardly to open circuit position by the latch 2|],previously mentioned, forming 'a part of the switch-operating mechanism M. The latch is pivoted at one end inside the housing 4| on a pin 45 and engages the plunger 44 intermediate its ends, the free end portion'of the latch extending through a slot 46 in the top wall of the housing so as to provide a handle portion for convenient manual operation of the latch. The latch has a notch 41 therein on that side thereof opposite the place where the plunger 44 at the switch It engages the latch. 68 is a rotary pendant member which also forms a part of the switch-operating mech- The pendant member 48 isin the form of a generally O-shaped rod pivotally mounted by its horizontal upper end portion 49 in bearings 50 provided therefor in the housing 4|, the member 48 normally hanging vertically.

with the lower horizontal end portion-5| thereof disposed in the same vertical plane in which the reset pin I8 moves but slightly above the circle of movement, as indicated in Fig. 5. However, when the member. 2| is kicked out to the position shown in Fig. 4, causing the reset pin l8 to move in the circle of larger radius, as indicated in Fig.

6,,the pin l8 in the rotation of the pulley will strike the lower end portion of the pendant member 48 and cause it to swing upwardly toward engagement in the notch 41 in the latch 20. Usually the speed at which the pin l8 strikes the pendant member 48 is enough to cause the latter to swing upwardly with sufficient force on the very first encounter to engage in the notch 41. At any rate, the second or third revolution of the pulley after it has been disconnected from the hub II] will certainly result in the pin l8 striking the pendant member 48 hard enough to move the latter to the full line position shown in Figs. 2 and 6. In the upward swinging movement of the pendant member 48, the bent end 52 slides along the straight edge 53 of the latch member 20, moving the latter from the inclined dotted position, shown at d in Fig. 2, to a substantially vertical position slightly to the right of the full line position of Fig. 2, but when the end 52 of the pendant member 43 rides into the notch 41, the latch 20 moves to the left under the action of the spring-pressed plunger 44, gripping the pendant member in the raised horizontal'position. In the movement of the latch member 20 from the dotted line position (i of Fig. 2 and finally to the full line position of Fig. 2, the plunger 44 of the switch I6 is moved to the right enough to snap the switch to off position, breaking the circuit for the motor driving the pulley ll. Promptly thereafter the pulley ll stops and everything remains at a stand still until the spike or other obstruction which caused the feed screw to jam is removed. Then, the reset pin 18 is depressed to move the kickout member 2| back to driving position, whereupon the latch 20 is moved to the right just enough to release the pendant member 48 holding the switch IS in open circuit position. Then, upon release of the latch 20, the plunger 44 moves outwardly under spring action causing the switch Hi to snap to closed circuit position so as to restart the electric motor driving the pulley II. It is obviously a much simpler matter to manipulate the reset pin l8 and latch 20 than to replace a shear pin. Replacement of a shear pin invariably required calling a service man, whereas the average stoker owner can by observance of simple instructions take care of everything from clearing out the obstruction at the feed screw to restarting themotor.

It is believed the foregoing description conveys a good understanding of the objects and advantages of my invention. The appended claims have been drawn with a view to covering all legitimate modifications and adaptations.

I claim:

1. A combination overload release mechanism and motor switch operating mechanism comprising, in combination, a motor driven drive member, a driven shaft having a drive hub thereon relative to which the drive member is adapted to turn freely, a drive projection on the hub, a kick-out member movably mounted on the, drive member having a drive projection thereon arranged to engage the aforesaid drive projecprojecting from the drive member for manual resetting purposes, a switch for controlling a motor circuit, and means for operating the switch operable upon engagement therewith by the reset pin, said pin being inoperative in relation to said means in the normal position of the kickout member.

2.. A structure as set forth in claim 1, including spring means for holding the kick-out member in driving position, and screw threaded adjusting means for varying the spring action so that more or less resistance to turning of the driven shaft will result in movement of the kickout member from driving position.

3. A structure asset forth in claim 1, wherein the last mentioned means comprises a swingable pendant member arranged to be struck by the reset pin to swing it upwardly from a normal dependant position to operatethe switch to open circuit position, and manually releasable latch means. for releasably locking the pendant member .in a' raised" position so as to keep the switch in open circuit position until manual release of the latch means.

4.. An overload release mechanism for a drive train, comprising in combination a drive member, a driven shaft having a driv hub thereon relative to which the drive member is adapted to turn freely, a drive projection on the hub,

a kick-out member movably mounted on the drive member havinga drive projection thereon arranged to engage the aforesaid drive projection on the hub to transmit drive from the drive member to'the shaft, said drive projections being formed to hav a cam action with respect to one another so that the kick-out member is moved from normal drive position when there is more than a predetermined resistance to turning of the shaft, and a leaf spring slidably engaging a portion of said kick-out member to hold it releasably either in driving position or inoperative position, the kick-out member being movable manually from inoperative to driving position. 5. An overload release mechanism for a drive train, comprising in combination a drive member, a driven shaft having a drive hub thereon relative'to which the drive member is adapted kick-out member movably mounted on the drive member having a drive projection thereonarranged to engage the aforesaid drive projection on the hub to transmit drive from the drive member to the shaft, said drive projections being formed to have a cam action with respect to on another so that the kick-out member is moved from'normal drive position when there is more than a predetermined resistance to turning of the shaft, a reset pin on the kick-out member projecting from the drive member for manual resetting purposes, spring means for holding the kick out member in driving position, and screw threaded adjusting means for varying the spring action so that more or less resistanc to turning of thedriven shaft will result in movement of the kick-out member from driving position.

I 6. "An overload release mechanismfor a drive train, comprising in combination a rotary drive member and a rotary driven member in coaxial relationship, one of said members having a sub stantially radial cam-shaped drive projection,

an elongated kick-out'member pivotally mounted at one end on the other of said members having a cam-shaped drive projection intermediate its ends arranged slidably to engage the first projection, whereby driv is transmitted from the driving to the driven member, and a leafl'spring detent cooperating with the free end of the kick-out member to hold the latter nor mally in drive position, the free end of the kickout member being slidable past the detent portion of the leaf spring against resistance of the spring when there is more than a predetermined resistance to turning of the driven member.

7; A structure as set forth in claim 6, wherein the leaf spring detent is of elongated form and rigidly supported at one end, the detent'portion being adjacent the other free end, and wherein the free end portion of said leaf spring is formed to provide a stop projection beyond the detent portion to limit movement of the free end portion of the kick-out member relative to said leaf springin the kick out movement.

v 8. A structure as set forth in claim 6, wherein the leaf spring detent is of elongated form and 1 rigidly supported at one end, the detent portion I being adjacent the other free end, and wherein thefree end portion of said leaf spring isformed to provide astop projection beyondtheidetent portion to limit movement of the free end porthe leaf spring to adjust the tension'thereof relative to the kick-out member and accordingly makeit more or less easy for the kick-out member to be kicked out.

10.'In a motor drive connection for a motor driven device, the combination of a housing for said-device, adriven shaft extending therefrom,

a drive pulley arranged to be driven by a belt from an electric drive motor, a hub drivingly connected with the shaft and rotatably mounting said-pulley, the side of said pulley toward the housing providing a recess annularly with respect to the hub, means providing a shoulder on the hub, an elongated kick-out member pivoted at one end tothe pulley in said recess and having a drive lug projecting there from intermediate its 1 ends for engagement with the driving shoulder, th drivingshoulder and lug being formed for sliding camming. engagement relative to one another so as to cause the kick-out member to be swung outwardly relative to the hub, spring detent means resisting outward movement of the kick-out member, a reset pin projecting from the kick out member in substantially parallel relation to the driven shaft, a motor switch adapted to control the electric circuit for the aforesaid motor driving the pulley, a housing for said switch mounted on the first mentioned housing adjacent the pulley, a pendant member for operating the switch pivotally mounted on the the detent portion to limit movement of the free 7 'end portion of the kick-out member relative to said leaf spring in the kick out movement, and screw threaded adjusting means cooperating with housing and hanging with the lower end thereof normally out of the path of movement of the reset pin but within the path of movement thereof when the kick-out member is kicked out, and

, manually releasable latch means for releasably locking the pendant member in a raised position withthe switch held thereby in open circuit position. V j

'11. A structure as set'forth in claim 10,'including screw threaded adjustable means for adjusting the tension of the spring detent means relative to the kick-out 'member, substantially asand for the purpose described.

12. A structure as set forth in claim 10, wherein the spring detent member comprises an elongated leaf spring rigidly supported at one end and having a detent portion on the other free end portion thereof arranged to be slidably engaged by the free end portion of the kick-out member, said spring being formed at the free end thereof to provide astop projection for engagement by the kick-out member in the'kicked out position, said leaf spring serving'yieldingly mounted'at one "end on the same member 'with' the kick-out element and having sliding engagement with a portion of said element at its other end to hold the elementreleasably eitherin driving position or inoperative position, said kick-out element being movable manually from'inoperative to driving position, and screw-threaded ad justing means on the same member with the kick-out element and leaf spring having engagement with the leaf spring at a point intermediate the ends thereof to increase or decrease the pressure of said leaf spring on the kick-out element.

14. A drive control mechanism comprising, in

combination with relatively rotatable driving and driven members, a kick-out element oscillatably mounted on one of 'said'members for movement to and from driving position, the kick-out element having a driving projection arranged to have sliding engagement with a surface provided on the other of said members, an elongated leaf spring mounted at one end on the same member with the kick-out element and having sliding engagement with a portion of said element at its other end to hold the element releasably either in driving position or inoperative position, said kick-out element being movable manually from inoperative to driving position, and screwthreaded adjusting means on the samermember with the kick-out element and leaf spring having engagement with the leaf spring at a point intermediate the ends thereofto increase or decrease the pressure of said leaf spring on the kick-out element.

15. An automatic control mechanism comprising, in combination, an oscillatable kick-out member, an elongated leaf spring rigidly sup ported at one end and having a stepped free end portion for sliding engagement with the free end of the kick-out member to hold it releasably on one step in operative position or on another step in inoperative position, the kick-out member being movable manually from inoperative to operative position, and screw-threaded adjusting means having engagement with the leaf spring at a point intermediate the ends thereof to increase or decrease the pressure of the stepped end portion of said leaf spring on the kick-out member.

16. In a motor drive connection for a motor driven device, the combination of a housing for said device, a driven shaft extending therefrom, a drive pulley arranged to be driven by a belt from an electric drive motor, a hub drivingly connected with the shaft and rotatably mounting said pulley, the side of said pulley toward the housing providing a recess annularly with respect to the hub, means providing a driving shoulder on the hub, an elongated kick-out member pivoted at one end to the pulley in said recess and having a drive lug projecting therefrom intermediate its ends for engagement with the driving shoulder, the driving shoulder and lug being formed for sliding camming engagement relative to one another so as to cause the kick-out member to be swung outwardly relative to the hub, spring detent means resisting outward movement of the kick-out member, a reset pin projecting from the kick-out member in substantially parallel relation to the driven shaft, and impact operated circuit control means for controlling the electric circuit for the aforesaid motor driving the pulley, said means being arranged to be struck by the reset pin when the kick-out member is kicked out.

17. A structure as set forth in claim 16, including screw-threaded adjustable means for adjusting the tension of the spring detent means relative to the kick-out member, substantially as and for the purpose described.

18. A structure as set forth in claim 16, wherein the spring detent member comprises an elongated leaf spring rigidly supported at one end and having a detent portion on the other free end portion thereof arranged to be slidably engaged by the free end portion of the kick-out member, said spring being formed at the free end thereof to provide a stop projection for engagement by the kick-out member in the kicked out position, said leaf spring serving yieldingly to hold the kick-out member in such position.

19. An impact operated circuit control means comprising, in combination with impact means rotatable with a rotary member, a swingable pendant member on an adjacent support arranged to be struck by said impact means to swing it upwardly from a normal dependent position to a switch operating position, a switch operable by said pendant member in raised position, and manually releasable latch means for releasably locking the pendant member in raised position.

20. An impact operated circuit control means comprising, in combination with impact means rotatable with a rotary member, a swingable pendant member on an adjacent support arranged to be struck by said impact means to swing it upwardly from a normal dependent position to a switch operating position, a switch having a spring-pressed plunger tending normal- 1y to move outwardly toward one extreme position but arranged to be moved inwardly to another extreme position when the pendant member is swung upwardly, and a latch member for releasably locking the pendant member in raised position While holding the plunger of said switch in the last-named extreme position, the spring pressure on said plunger causing said latch member to grip the pendant member resiliently.

FLOYD R. NELSON.

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