CA1040120A - Overload clutch - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

In a totally enclosed adjustable overload clutch located between a driving and a driven member, in which a cam follower is so mounted with respect to a cam plate as to permit the driving member to rotate when the driven member is overloaded, without disengaging the cam follower from the peripheral surface of the cam plate, without destroying the clutch;
the cam follower being reseatable in a seat in the periphery of the cam plate simply by rotating one of the driving and driven members relative to the other in either direction, without access to the interior of the enclosure; there is provided an overload detector assembly mounted outside the enclosure in such a way as to respond immediately to overload, without repairing any electrical or mechanical interconnection with elements of the cam assembly inside the enclos-ure.

Description

L.~ 1,.20 This application is a division of copending application No.
238,940 filed November 4, 1975.
Overload clutches, positioned between a rotating driving member and a rotated driven member to prevent damage when the driven member is prevented from rotating, are old and well known. Illustrative examples from the patent art include U.S. Patents to Duncan et al, No. 1,441,491, Aldeen, No. 1,548,427, Landahl, No. 2,202,497, Babaian, No. 2,753,029, Hall, Reissue No. 23,361, Lutz, No. 3,561,576, Zanon, No. 1,391,601 and Gerstung, No.

2,826,903.
Conventional overload clutches have either been arranged to throw out a cam follower, as by a latching pawl arrangement, of which Duncan et al and Aldeen, above, are typical examples, or by an overcentering arrangement, of which Landahl is an example, or a catch, such as is shown in Hall, or they have been arranged to break a circuit to stop the rotation of the driving member, as in Babaian. These arrangements have required easy access to the cam follower assembly, to permit the cam follower to be restored to its engaging condition.
In Lutz, two cam followers are moved axially with respect to cam seats in the cam plate and a circuit breaking arrangement is provided, which permits restoration of the cam follo~ers to the seats by rotation of the driving and driven members in the opposite direction from the normal direction of rotation.
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In Zanon, three simple spring loaded detents pro~ect into notches and are said to permit relative rotation of the driving and driven members.
Even in the Lutz and Zanon devices, the overload clutch is exposed.
Gerstung shows an extremely simple arra~gement of a U-shaped spring, the legs of which embrace a non-circular cam, all of which is enclosed in a housing. The releasing of the Gerstung clutch depends upon the bowing of the legs of the spring.
In the prior art devices, either the cam pla~e has been made of a small radius, to permit the accommodation of follower biasing means in the same plane, or the cam follower has been cantilevered.
As a result of the use of the various constructions described, the overload clutches have not been sealed and permanently lubricated, and for most of them, it has been necessary to reach into the mechanism to restore the cam follower to its engaging position.
In those of the prior art devices in which provision is made for overload signalling or automatic power cut-off, the ~0 mechanism has been actuated by a lever or other movable support for the cam follower, This has necess~tated either leaving the lever exposed, as in Lutz, or partly exposed~ as in Babaian/ in which the cam follower must be in the part of the clutch ~(~4~;20 connected to the driving member, or else making provision for sliding electrical contact as in Grohn, No. 2,003,115.
In the copending application No. 238,940, an overload clutch is provided of the type in which a driven member is releasably connected to a driving member by means of a spring loaded follower, mounted on one of the members, normally engaged in a seat in a cam plate mounted on the other of the members. A generally circular cam plate, narrow in its axial dimension compared with its radial dimension, is provided with a seat in its periphery.
A housing, rotatably mounted on the hub, completely encloses the cam plate.
The housing has within it a lever cavity defined by spaced side walls of said housing, spaced, aligned journal wells opening through said side walls, on opposite sides of the cam plate and a spring well opening into the lever cavity at a point axially displaced from the cam plate. Anti friction bear-ings are provided between the housing and the hub to provide bearing surfaces for relative rotation between the housing and the hub. Annular seals are provided between the housing and the hub outboard of the anti-friction bear-ings in both axial directions. A dog-leg lever is mounted in the lever cavity ; on a shaft journaled in anti-friction bearings mounted in the journal wells.
- The lever has a yoke at one end with arms positioned at either side of the axial extent oE the cam plate and a leg on the o~her side of the shaft from the yoke extending, at an angle, to a position axially clear of the cam plate at the end of the leg opposite the yoke. The yoke arms carry a pin, upon which a roller-follower is rotatably mounted on anti-friction bearings, the roller-follower normally seating in the cam plate seat. A compression spring seated at one end in the housing spring well, bears at its other end upon the lever leg at the end of the lever leg axially clear of the cam plate.
The present invention is directed to an overload detector assembly outside of the housing. It includes a segmented flat annulus, mounted on the outside of the housing, the segments of which are slidably mounted for limited radial movement and biased radially inwardly, and an annular cam hub, mounted on the clutch hub. The radially inner edges of the segments of the annulus and the radially outer edges of the detector cam hub have complementary projections and indentations in which the projections seat. Upon relative rotation of the annulus and cam hub, the projections are driven from the indentations, moving the segments radially outwardly to actuate a control, such as a micro switch or hydraulic, pneumatic or mechanical control or signal.
; The totally enclosed overload clutch is simple in operation, rugged~ effective over a wide range of speeds and economical. The clutch eliminates the need for a hold-out mechanism. Further the clutch is bi~
directional and can be made with equal release torque in both directions or selectively greater release torque in one or the other direction.
Thus the totally enclosed clutch with the overload detector assembly of ehe preeent iDventlon requires no access to the interior of the clutch enclosure. The assembly is light, simple, immedlately responsive in any and every position and dependable.

Brief description of the Drawings In the drawing~, Figure 1 is a view in end elevation, partly broken away, of one illustrative embodiment of overload clutch of this invention;
Figure 2 is a sectional view taken along the llne 2-2 of Figure l;
Figure 3 is a sectional view taken along the line 3-3 of Figure l;
Figure 4 is a fragmentary sectional view illustrating one coupling arrangement between a drive shaft and a driven shaft through an overload clutch of this invention;
Figure 5 is a view in end elevation of an overload clutch of this invention, slightly modified and provided with one embodiment of overload detector assembly of this invention; and . Figure 6 is a view in side elevation of the exterior of the enclosing housing of the overload clutch of this invention with the overload detector assembly of Figure 5 shown in section t~ken alotg the line 6-6 of Fig~re 5.

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Description of the Prererred Embodlment Referring now to the drawlngs for one illustratlve embodiment Or overload clutch Or thls lnvention, rererence numeral 1 indicates an overload clutch which, ln this embodiment, is shown as connecting a sprocket 2 to a shaft, not here shown, the end of which is mounted in and keyed to a hub 10. The hub 10 ls cylindrlcal, and its internal construction is conventional.
A cam plate 20 is made integral with or securely mounted to the hub 10 against roation relative to the hub, intermediate the two ends of the hub.
The sprocket 2 is mounted on an outside face Or a wall 31 o~ a housing 30, which is rotatably mounted on the hub 10 and ~ completely encloses the cam plate 20.
!. The housing 30 has a circumferential wall 32, which, ? 15 ln this embodiment, is integral with the wall 31, and a side ; wall 33, bolted a~ainst a flat annular radial face Or the circumferential wall 32, in liquid tight engagement therewith.
In the lnterior of the housing 30, the walls 31, 32 and 33 define an annular lever cavity 34, within which a dog-leg lever 50 ls ~ `` 20 mounted.
¦ The wall 31 has a heavy section in which an axially directed ~ournal well 35 ls formed. A ~ournal well 36 in the wall 33 extends, in this embodiment, through the wall 33, and is axially aligned with the ~ournal well 35. The ~ournal well 36 is closed at its outboard end by a cap 63. In another heavy , OlZO

section or boss Or the wall 31, a sprinr, well 37, tendln~, chordally, with its axis substantlally parallel wlth flat slde races Or the cam plate 20, extends through the housing wall 32 at one end and opens at its other lnto the lever cavlty 34. The spring well 37 is internally threaded throu~h a part of its length from the end which extends through the wall 32, to take an externally threaded ad~ustlng nut 38. The adJusting nut 38 has an allen wrench socket 39 in lts outer surface, and when screwed into the threaded end of the sprln~ well 37, ti~htly closes the end Or the well.
- An axially projecting annular rib 40 extends lnboard rrom the side wall 33, and has a rlat radial race 41. An axially proJecting annular rib 44, of which the spring well boss is a part, with a flat radial face 45 extends inboard from ~ 15 the side wall 31. The faces 41 and 45 derine between them ; an annular passage through which the cam plate 20 extends.
Thrust washers 80 are interposed between the ~aces 41 and 45 and the flat side of the cam plate.
The radially inner face Or the rib 40 ls stepped to rorm a raceway channel 42 and a seal groove 43. The radially inner side Or the rib 4ll is similarly stepped to provide a raceway channel 46 and a seal ~roove 47.

4~2~1 Needle bearlngs 48 are mounted in both of raceway channels 42 and 46. Seals, which ln the embodiment shown are in the form Or 0 rings 49, are mounted in the seal grooves 43 and 47, axially outboard Or the needle bearings 48. It will be understood that the needle bearings 48 wlll normally be caged in their own raceways, whlch wlll be snugly mounted in the housing raceways 42 and 46, and on cylindrical outer - surfaces Or the hub 10 on elther side Or the cam plate 20, to provlde antl-friction bearings between the housin~, and the hub, for rree rotation Or the hub and housing with respect to one another. The 0 rin~s 49 bear snugly against ~ralls of the housin~
and smooth cylindrical surfaces Or the hub 10.
The cam plate 20 is bounded axially by flat, smooth, parallel radial side surraces 21 and 22 and peripherally by a rlat peripheral surface 24, lnterrupted, in the illustrative embodiment, by a single seat 45. The seat 45 is an arc Or a circle.
The dog-leg lever 50 has at one end a yoke 51, with arms 52 and 53 spaced ~rom one another, and carrying between ~4a)~%0 them a pin 5ll, upon whlch a roller-follower 60 ls mounted on roller bearlngs 55. The arms 53 and 52 are inte~ral wlth a knuckle 56 mounted on a shaft 57 ~ournaled ln needle bearlngs 58 in the Journal wells 35 and 36. A leg 59, integral at its one end with the knuckle 56 extends at an angle from the plane o~ the side faces of the cam plate 20 to a point axially dis-placed from the cam plate, and in line with the axis Or the ; spring well 37. The free end of the leg 59 is withln the lever cavity 34, a short distance from the open inner end of the sprin~ well 37.
A helical compression spring 70 is mounted in the sprin~ well 37 with one end abuttin~ the inside face Or the nut 38 and its other end abuttin~ an annular flange on a plun~er 75. The plun~er 75 has a stem 7~ which is slidably embrac,ed within the helical compression spring 70 and a head 77 the outer surface of which bears a~,ainst the lower end Or the le~ 59 of the lever 50. The compressive force Or the sprin~
70 aF,ainst the le~, 59 can be varied by screwin~ the nut 38 ln or out.

-- ~0 --~046~20 As will be seen from Fi~ures 2 and 3, the roller-follower 60 is centered axially on the cam plate 20, and as seen from Flgure 1, ls of substantially the same radiu~ as the seat 45 so as not to bottom ln the seat. The yoke arms 52 and 53 are symmetrically arranged wlth respect to and axlally outboard of the cam plate 20 on either side thereof.
The lever cavity 34 is filled with lubrlcant, and the ti~htness of the housin~ walls and the arrangement of the sealing 0 rin~s 49 provides for substantially permanent lubri-cation Or the elements within the housing.
The arrangement of the leg 59 and compression sprin670 permits the use of a relatively lar~e diameter cam plate 20 with a compact housin~. The provlsion of a totall~ enclosed, sealed housin~ permits, as has been indicated, permanent lubri-cation. Most importantly, the yoke mounting of both theroller-follower 60 and the do~-leg lever 50, with the anti-friction bearin~s ~ournalin~ both the roller-follower and the lever shaft, permits the follower and cam plate to rotate with respect to one another when a ,~am occurs, freely and for all practical purposes, inde~initely, without dama~e to the cam plate~ the follower, or any other component of the clutch. The clutch can be reset, after the ~am is cleared, simply by rotating one Or the housing and hub members with respec~ to the other in either direction, until the roller~follower seats in the seat 45.

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While the sprocket 2 is merely illustrative o~ a means for transferring power to or from the clutch, this p~rti-cular arrangement of mountlng the sprocket to the housing permit~ the use of a simple chain coupling arrangement with substantial advantages.
As shown in Figure 4, a sprocket 202 with a hub 203 keyed to a shaft 211 is connected to the sprocket 2 by means of one half of a cha~n coupling 215, of a well known, readily available type3 which provides reliable and inexpensive coupling with ample accommodation of misalignment, utilizing the existing sprocket mounting surface.
Referring now ~o Figures 5 and 6 for one illustrative embodiment of detector assembly 120 of this invention, mounted on the side wall 33 of the clutch housing and a hub 110 which is identical with the hub 10 shown in Figures 1-4 except for a longer axial extent, beyond the outside face of the side wall 33, and, in this embodiment, three set-screw receiving sockets 111.
The detector assembly 120 includes an annular cam hub 121, with set-screw passages 122 corresponding to set-screw receiving sockets 111, and circumferentially regularly spaced radially outwardly extending projections 123. The cam hub 121 i9 mounted tightly on the hub 110 and close to the outer face of ~¢~f~20 the side wall 33 as shown in Figure 6.
~ segmented annulus 130 is made up of three segments 131, 132 and 133 spaced slightly from one another and slldably bolted to the outer face of the side wall 33 by means of bolts 140.
Bolts 140 are three of the bolts by which the side wall 33 is bolted to the wall 32 of the housing, and are spaced 120 apart. The bolts 140 are longer than the rest of the side wall bolts, and are tlghtened against spacer sleeves 141, which extend through slots 134 in the segments 131, 132 and 133. The slots 134 are wider and radially longer than the sleeves 141 but narrower than a spring washer 142 between the head of the bolt and the sleeve.
Each of the segments, which are identical, has an outer flange 135 turned toward the clutch housing and normally bearing against an axially extending surface of the perimeter thereof. Each also has two, integral, struck out tabs 136, raised from the surface of the segment and open at their radially outer ends, and two inaen~ations 137 in its radially inner edge positioned complementarily to the projections 123 on the cam hub. The abutment of the flange 135 provides some clearance, somewhat exaggerated in Figure 5, between the outer perimeter of the cam hub 121 and the projections 123 and the inner perimeter of the segments and their indentations.

The segments are biased radlally inwardly by a cir-cular spring 150l seated a~alnst a shoulder 138 of each tab136.
The sprlng 150 is strong enough to prevent movemen~ Or the segments ln response to centrlru~al force at any intended speed Or rotation of the clutch.
As can be seen, the segments 131, 132 and 133 making up the annulus 130 are very thin. They transmit no turning torque and can be made of light metal or plastic, as can the cam hub 121.
When the clutch housing 30 and hub 121 start to rotate with respect to one another, the pro~ections 123 Or the hub will move out of the indentations and cam all of the segments radially outward at once, the movement being indicated in broken lines in Fi~ure 6. Thus, at any and every position, the detector assembly will react immediately to actuate a movement responsive control such as a micro-switch 160 lndicated somewhat diagrammati-cally in Figure 5. The "control" can perform either a sig-nalling or operating function.
The li~htness of the detector assembly means that it adds only ne~ ible mass to the clutch and allows for a compact design, important considerations ~or repeated stop-start appli-cations where inertia is important.

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Numerous variations in the construction of the overload clutch and detector assembly of this invention w~ll occur to those skilled in the art in the light of the foregoing disclosure.
Merely by way of illustration and not of limitation, more than one follower seat can be provided, spaced angularly from the first seat.
The seat 45 itself can be made assymetrical so as to make the release torque different for the two directions o rotation, and deeper or shallower or of different configurations to change the release torque characteristics. By in effect utilizing two housing members of the construction shown on the right side of Figure 2, rotated through 180 in both directions, modifying the housing members to provide for another appropriate lever shaft journal well, and providing a second seat in the cam plate a two roller, plural seat device can be produced. However, the single follower - single seat arrangement of the preferred embodiment has advantages of simplicity and automatic angular orientation of the hub and housing not available to the more complex arrangements with a plurality of seats or followers. Different housing seals can be employed, the 0 rings 49 being simple and effective, but not the only types which can be used. Some or all of the lndentatlons of the segments of the detec~or annulus and the projections of the cam hub can be reversed, or made different sizes and shapes.

to produce greater or less travel Or the segments. The numbers of se~ments making up the annulus can be varied rrom two to any greater number, althou~h three or four are prererred. The rim Or the annulus can be turned outwardly, although the lnward turnin~ has advanta~es Or servln~ the dual runctlon Or stop and control element bearin~ track and Or being more compact. The biasin~ Or the segments can be accomplished by the use Or other types of sprin~s. Ir a manual reset is desired, the sprin~ bias can be eliminated and a sprin~ washer or the li~ce used to hold the segment in place until the se~ment is cammed out and subse-quently manually forced back when the blocka~e is cleared. If the clutch hub does not proJect beyond the face Or the side wall, the cam hub can be mounted on the shart, but the prererred embodiment is unitary and compact. These variations are merely illustrative.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In an overload clutch connected to a shaft, said clutch being enclosed by a housing having a radially extending side wall the improvement comprising a cam hub mounted to rotate with said shaft, an annulus mounted on the outer face of said side wall and a movement responsive control device, said annulus comprising a plurality of segments, all radially slidably mounted on said outer race of the side wall of the clutch housing and each having a radially inward surface adjacent and racing a radially outer surface of said cam hub and a radially outer sur-face constituting a bearing track, said inner surface of said segments and said outer surface of said cam hub having com-plementary projections and indentations normally nesting in one another, means for yieldably maintaining the segments in a radially inward position at which the said projections and indentations nest, said projections and the surface defining the indentations serving to cam the segments to move them radially outwardly when the cam hub is rotated with respect to said segments, and said control device having means, positioned contiguous the segments bearing tracks to be operated by said outward radial movement of said segments.

2. The improvement of claim 1 wherein the annulus is made of thin sheet material, and the radially outer surface is constituted by a flange turned from the plane of said sheet.

3. The improvement of claim 2 wherein each of the segments making up the annulus has at least one tab struck out at its radially outer end, and the means for yieldably maintaining the segments in a radially inward position comprise a circular spring seated on a shoulder of said tabs.

4. The improvement of claim 2 wherein the said flange is turned toward and embraces a surface of the periphery of said housing.

5. The improvement of claim 2 wherein the projections and indentations do not touch when normally nested.